CQ CQ CQ de W0VLZ

AWA 2012 Linc Cundall OT CW Contest

2012-01-22T21:27:00.017-06:00

This afternoon I wrapped up my participation in this year's Linc Cundall OT CW Contest. Obviously I'm not a major contester. During the 48 hour contest I netted nine contacts. Not many contacts/points but I did enjoy putting my latest homebrew transmitter on the air.

This year I used my new "Taylor 75", a 1934 style oscillator-buffer deck driving two Taylor TZ-20s in push-pull. The receiver was a National NC-101X. Everyone that commented indicated that the transmitter sounded fine. Keying the buffer stage helped. With the crystal oscillator running continuously (on transmit) there was no sign of chirp.

I went ahead and created a QSL card to send out.

On the Air

2012-01-14T19:31:00.003-06:00

Today I got on both 80 and 40 using my new 75 watt transmitter. This afternoon I had a nice QSO on 40 with KC9RXI, Tom, in West Salem, WI and this evening on 80 with NS7E, Art, in New Prague, MN. Both Art and Tom reported no problem with my signal.

Tremendous!

It Works!

2012-01-12T20:09:00.019-06:00

After a couple of days scratching my head and asking around trying to figure out why my TZ-20 amplifier wasn't working up to expectations I finally did what I should have done first. I checked the wiring.

One TZ-20 wasn't connected to the final tank coil. I was running with only half an amplifier and a poorly designed one at that. It worked but not well. Once I fixed the wiring error power levels jumped to the 50-60 watt range. Neat, but now I needed to deal with typical amplifier problems.

TPTG feedback -The first problem I had was that the amplifier took off on it's own (without any drive) when the input/grid circuit was peaked for maximum output. This was solved by removing C3, the TZ-20 grid tuning capacitor, from the circuit. C3 in the amplifier and C8 in the final tank circuit of my 1934 transmitter interacted anyway so this eliminated one pesky control. Problem solved but now the drive level was way down...one solution led to another problem.

Drive level - With no tuned circuit on the grids of my TZ-20s they were not getting the drive needed to get anywhere close to full output. This one was solved with a new coil for L1/L2. More turns for L2 got the power transfer up to the point that now I'm easily driving the amplifier to 75 watts input.

Bias - This all started with me wondering if I has the bias set right. The advantage of the TZ-20s is that they do not need an external bias supply to protect them when the drive goes away. With no drive (and no bias) plate current drops to almost zero. For the TZ-20 a simple resistor from the grid to ground is all that's needed to produce needed bias....but what value? It turns out that the 1939 Taylor tube manual has a formula for calculating recommended Class C CW grid bias for a given plate voltage, in my case 500V. Bias came out approximately 20 volts. I'm driving the grids to about 30mA ... 20V/30mA = 666 ohms. I had a 750 ohm resistor, close enough.

One question that had to be dealt with was how best to couple the output to the antenna. It turns out that, for my 40 turn tank coil, a four turn link gives me maximum output into my 50 ohm dummy load. I am set up, though, so that I can add a loading capacitor in series with the link to cover real world antenna conditions.

Now I have an amplifier for my 1934 transmitter that takes about 6 watts of drive to run 75 watts input (45-50 watts output) on 80. With a couple of new coils I should be able to put it on 40.

Look for me during the AWA Linc Cundall OT CW contest next week.

TZ-20 Operating Specs?

2012-01-07T08:47:00.008-06:00

I've gotten my TZ-20 RF amp up and running with my three tube 1934 transmitter but its not working like I expected.

I'm running with 500V on the push-pull plates with the recommended 2K bias resistor. Key down I'm seeing grid current (total for the two tubes) of about 40mA and total plate current of 40-50mA. Looking at the TZ-20 specs and tubes curves from the 1939 Taylor Tube manual I expected to see 50-75 watts input with 35-50 watts output, instead I'm seeing 20-25 watts input and only 8-10 watts output. I do have three TZ-20s. Any two of them behave the same. What an I doing wrong...or is it working as designed?

Elecraft KX3 On Order

2011-12-30T20:53:00.015-06:00

It's winter here and I'm already thinking about spring!

After 10 years I'm retiring my faithful K1 for a brand new Elecraft KX3. See http://www.elecraft.com/KX3/kx3.htm for the details.

I'm excited. The KX3 It covers all amateur bands, 160-6 meters, operates phone, data and CW, and is DSP-based. It will allow me to do digital/PSK31 from the picnic table without an attached computer and the the receiver looks like it should be great.

The first thing on my list was the ATU. With it I can easily load into my favorite end fed half wave antenna. I ordered the KX3 assembled to make certain everything was aligned right and that it worked straight out of the box. The internal charger will make it easier to do really spur of the moment operating. Finally, why the mic? The rig supports CW, phone and data. This will allow me to try a little QRP phone operating, especially if demoing the rig.

I decided to wait on the roofing filter. I'll see how it works as is. I'm not a big contester or pileup operator so I tend to move away from the QRM but sometimes it comes to you. I can always spend the $130 for the filter later.

---------------------Order Summary-------------------------

Item Subtotal: $1269.80
Shipping Cost: $15.68
GRAND TOTAL: $1285.48
NOTE:Customer declared exemption from 93.20 sales tax.

Shipping Method: UPS Ground [55901]
Shipping Weight: 5.50

-----------------Individual Item Breakdown-----------------

Item Ref. Price ea. Qty. Description

KX3-F $999.95 1 KX3-F 160-6 M Transceiver (Assm)
KXAT3 $149.95 1 KXAT3 ATU for the KX3
KXBC3 $59.95 1 Int. NiMH Charger/Clk for KX3
MH3 $59.95 1 MH3 Hand Mic. for KX3

------------------------End of Order-----------------------

Unfortunately the estimated ship date is almost two months away. I'll have to wait.

AWA Bruce Kelley Memorial CW QSO Party

2011-12-12T09:26:00.013-06:00

The last two weekends I operated in the AWA Bruce Kelley 1929 QSO Party. This is always a great time to get an early rig on the air and work others doing the same.

On the first weekend I operated as K5CF from Poteau, OK using Vance's type TNT transmitter running about 6 watts using a single type 10 tube. While I heard W0LS, KB0RON, N8YE and KB0MM fairly well I could never get a response to my calls. Power out looked OK so Vance's Gap Titan DX vertical on 80 may have been the problem.

This past weekend I was back in Rochester, MN using my Hartley transmitter to make ten contacts. This event allows any receiver to be used. This year I used my 1941 simple superhet. I have only a fairly low end fed wire antenna and my contacts reflected this. Seven were right here in MN, two were in OH and one "DX" contact was in SC.

What might I change? The antenna is always an issue. I have a 29' base loaded vertical this winter but the recent snow seems to have detuned it. I'll need to check it out before the LC CW Contest in January.

More TZ-20 Amp

2011-11-09T08:19:00.007-06:00

I've finished the wiring. Now I need to cobble together a power supply and I'll be ready to test it.

My deadline is about two months away, the January AWA Linc Cundall CW Contest. Two years ago I did ok with my 1934 transmitter running barefoot, this time I'd like to add 75 watt "boots".

A Strain Relief for an End Fed Wire

2011-10-30T13:23:00.010-05:00

Once a friend asked about how to anchor an end fed antenna ( such as an EFHW ) at the rig end. A lightweight QRP rig attached to a 67' long wire slung over a high tree limb won't stay put without help. I solved the problem with a "split bolt connector" and some nylon twine.

I found split bolt connectors in the electrical department of my local big box hardware store. The nut, with it's captured cross-piece, screws onto the slotted bolt.

I cut off a couple of feet of nylon twine and looped each end. One loop goes into the split bolt.

Looping the twine around a convenient object (in this case a porch railing) and securing it gives a solid anchor for an end fed wire.

On the Air with my Hartley

2011-10-28T11:36:00.005-05:00

The AWA 1929/Bruce Kelley CW Party is coming up the first two weekends in December and the weather has started to cool off here in Minnesota. I've put the K1 back into it's winter operating position (a top the 75A4) and started to warm up the classics.

Right now I'm running my Hartley paired with my 1940 Simple Superhet. They make a good pair but my signal reports remind me of one of the Hartley's main limitations. On the 18th I worked Lynn, NG9D. Lynn commented that my signal had a fast QSY to it. Last night I worked Dave, WA9DOF. Dave reported that he wouldn't have known the transmitter was a vintage rig if I had not told him. The difference was the wind. Last night we had no wind here while on the 18th the wind was 10-15 mph. The antenna blowing in the wind shifts the load slightly that it presents to the transmitter. This in turn pulls the frequency slightly. Lightly loading the rig when tuning up helps (see my Nov 16, 2009 Blog entry) but wind can still be a factor. Pulling my wire antenna tighter or a completely new antenna might be needed. I'll see what I can do.

Another Chance to Operate QRP

2011-10-06T16:06:00.014-05:00

Beth and I try to get away at least once a month. Almost always I pack along my K1 (and Beth, a good paperback). This time I also had along my Crappie Pole 20 mtr C-Pole vertical.

Last weekend we took the trailer down to the Wisconsin Dells, about 150 miles southeast of Rochester. Besides doing some of the the usual tourist stuff (and there is a lot of it at "the Dells") I got on the air, both from the campground and from an I 90 Rest Stop at the Minnesota/Wisconsin border. Stations worked included KF4IZE, K4ZH, WG0AT/P (A real high for the weekend. See Steve's video report here), WA3SEE and KI4UUZ. The weather was great for sitting at the picnic table with the K1 and I had no problem making a few contacts.

With cooler weather approaching my picnic table QRPing will move into the basement and start to split time with the boat anchors...but we'll still see what can be done outside this winter for the Arizona ScQRPions FYBO contest.

QRP on the Road

2011-08-23T14:39:00.005-05:00

Beth and I just got back from a trip covering 4900 miles in eleven western states. I had packed my K1 and 67' end fed wire antenna so I operated along the way. QTHs included Pt Defiance (in Tacoma, WA), Paradise (on the south side of Mt Raineer) and West Cliffe, CO (south of Denver). I worked WA7NCL, N7MOB, K0FTC, KD6L, W6LOH, KK4IP, N5RDN, KG8YT, KD8A, WB0UFF, W4HEX in nine states. Signals on 20 tended to be a down but it was still fun to get on the air and see who I could work. My most memorable contct was with W4HEX, Will. He was operating mobile CW near Mongomery, AL. At the time he was using his K2 and a Hamstick on his pickup but backup rigs included a K1 and a K3.

3S4 QRP Midget

2011-05-19T10:36:00.006-05:00

Last week I paid a visit to my friend Skip, K7YOO, in Winona. While rooting around in his parts storage I noticed a little transmitter. I've a weakness for QRP homebrew and this one, with miniature tubes, is of an era I don't have covered. A couple of days ago Skip dropped it off here in Rochester as he headed for the airport.

It is a version of the "QRP Midget" first described in July 1967 Popular Electronics by W5LET. Dave Ingram also covered it in November 1992 CQ. This one is build in a little bigger box with an added current meter and RF choke in the B+ line but otherwise it is a good copy of the original.

This transmitter uses tubes designed for battery powered portable radios common just before transistors took over the market. Two "power" pentodes in parallel run about a watt out on 80 or 40...not a barn burner but it should be good for some contacts.

Now I need to come up with a receiver along the same lines...

Spring at Last!

2011-05-04T17:07:00.006-05:00

Spring is here at last, but I did have to drive 150 miles to find it.

Some extra time in my travel schedule today gave me the chance to do my first Picnic Table QRPxpedition of 2011. The I90 rest area just outside of Mauston, WI turned out to be fine place to stop, have some lunch, throw the antenna up into a tree and see who I could work. Mark, KQ0A, in Taos, NM heard my "QRL?" on 14.060MHz and gave me a call. He was 599+ the entire QSO while he gave me a 579 with some QSB.

With the solar cycle heading up I'm planning a lot more great QRP QSOs this summer.

More TZ-20 Amplifier

2011-03-15T16:35:00.015-05:00

My TZ-20 Amplifier project has been on hold waiting for some sort of rack to mount it above my 1934 transmitter. I finally got some help from Skip, K7YOO, to cut and bend a piece of 16 gauge aluminum to form the shelf. 1" angle aluminum is used for the vertical legs and the shelf supports.

Once warm weather returns to Minnesota I'll take the rack apart and give it a few coats of paint, probably black wrinkle to match the rest of the station.

Winter 2011 CX

2011-01-31T22:06:00.012-06:00

Yesterday was the Winter 2011 Classic Exchange. This event offers a great chance to get on the air with older gear. Participants putting multiple vintage transmitters and receivers on the air have a big score advantage, but it's fine to put only one vintage station on the air or work others using, even, a software defined Flex-5000A.

This year, after going through the possibilities, I settled on five stations I'd like to have in the CX:

Drake R4B/T4XB
Collins 75A3 / EF Johnson Navigator
NC270 / Eico 720
NC303. EF Johnson Ranger II
NC101X / 1934 "46 Job"

In all I made 11 contacts (but only 10 counted for points) and I used 4 of my 5 stations. The CX gave me a chance to play with a couple of radios I haven't used in a while and to fine tune a little what I'm looking for in my favorite "boat anchor" station.

2010 AWA Bruce Kelley QSO Party

2010-12-18T17:00:00.006-06:00

The last two weekends I participated in the AWA Bruce Kelley QSO. Except for curious visitors, transmitters must be limited to 1929 (or earlier) designs and not crystal controlled.

This year I used my Hull Hartley at 10 watts input and a Drake 2B receiver. The change from last year was having a 80 mtr vertical available rather than a simple end fed wire. Unfortunately SE MN was under a blizzard warning for most of the first weekend of the party and I was busy elsewhere for most of the second weekend. Self excited oscillators like the Hull Hartley are prone to frequency wobble whenever the antenna load changes. My vertical swaying in the blizzard wind was too much for it. Rather than wobble all over the band I again used my 105' end fed inverted "L".

Even with only 3 watts out to a low (10' -15' off the ground) antenna I made 11 contacts and worked both east and west coasts. I had a good time.

Maybe next year I'll have an amplifier for my Hartley so that I can use the vertical (with the sway) and run closer to 6-7 watts out.

80 Mtr Vertical Performance

2010-12-09T08:18:00.020-06:00

I wondered if my 80 mtr top loaded vertical is a good antenna for the Bruce Kelley Memorial 1929 CW QSO Party. Part of the loading is the top 6' of two of the guys. Any sway at all causes a guy to sag a little shifting the load my Hartley sees. This causes my signal to FM/wobble...distracting to say to least and aggravating if the band is crowded. I needed to know if the gain offered by the vertical over my endfed wire was enough to outweigh the the wobble it introduced.

The reverse beacon network at http://www.reversebeacon.net/ allowed me to get a good idea of real antenna performance. All I had to do is call CQ and any reverse beacon stations hearing me automatically posts my call, frequency and signal strength to the web. By switching between my low endfed wire and my vertical I could get a good A vs B comparison. By doing this over a period of time I could see how changing nighttime propagation impacts this comparison. Monday night I did exactly this and then sorted though the data to see how the two antennas compare from about 8PM (2:00 UTC) through the next morning.

What I found was that for the east coast (PA) the vertical offered 4-5 dB gain throughout the night. While not a spectacular performer it is almost always better than my endfed wire...but signal reports all mention the wobble/FMing introduced by antenna sway. Based on this I'll stick with my endfed wire for the early evening hours and then switch after about 10PM when the band activity dies down a little.

For next year's Bruce Kelley QSO Party it would be nice to have this problem solved by building a '29 style amplifier to use with my Hartley. Fortunately my 1934 transmitter already has an amplifier stage in between the oscillator and the antenna. My vertical will work fine with this transmitter during the AWA Linc Cundall Memorial CW Contest in January.

More 80 Meter Vertical

2010-11-06T09:59:00.014-05:00

Yesterday I did the final pruning on my 80/40 meter vertical.

This antenna is a big improvement over my 105' endfed wire. Last night on 80 CW running only about 10 watts I worked KK1K (VT), VE7SL (BC) and VE3AWA (ONT). All gave me good signal reports and had no trouble with the QSOs. In addition VE7SL reported I went from s6-s7 to unreadable when switching back to the endfed wire. VE3AWA reported that I went from s9 plus to s8 when switching to the endfed wire.

I also checked my antenna performance used the Reverse Beacon Network at http://w ww.reversebeacon.net .This is a network of receivers/computers connected to the internet. They auto log the frequency and signal level of any CQs heard. By calling CQ using both the vertical and the endfed wire I got a good idea on how the two antennas compare. The network consistently logged me when I used the vertical and never heard me when I used the endfed wire. At the locations on the Reverse Beacon Network, the vertical was the clear winner. But there were no reverse beacon stations in MN, WI or IA. My endfed wire might have done better if evaluated using nearby reverse beacon stations locations.

I was asked about my radial system. I have eight 30' insulated wire radials stapled in the grass. 30' seems short, I expected to need 67' (1/4 wave on 80) long radials. I measured the resonant frequency of the radial system as I would an 8 element fan dipole with two 4 element halves. 30' seemed to be right. Velocity factor must have a big impact on the length of ground mounted radials.

This new vertical should definitely help my AWA QSO Party scores.

More 80 Meter Vertical

2010-10-11T20:02:00.010-05:00

Beth has commented that I need to get a "Frequent Buyer" card for my local big box hardware store. Since starting on this project I've been making trip after trip to buy yet one more bunch of screws, a particular clamp, a spool of wire, a ..... the list goes on. For a project that started with a $7 set of fiberglass poles this one certainly is a great example of "the devil's in the details".

I'm finally to the point of pruning it to frequency. Along the way I've fashioned a hinged base out of a large gate hinge and two conduit hangers, I've added 40 meter capability and I've made the bottom 24' a four wire vertical cage. Top loading is provided by two 6' elements forming the top ends of two of the guys, a coil wound out of 14 gauge insulated wire on a piece of 4" thin wall PVC sewer pile and a vertical 6' element. 40 meter coverage is provided by a 9' stub (connected directly to the top of the 24' vertical cage) that makes up the top of the third guy. Additional support is provided by tying the mast to my deck railing at approximately the 9' level.

Normally this will be a winter installation. I plan to paint the mast white.

Actual on the air reports will need to wait until I finish tuning it to 3560KHz.

80 meter vertical

2010-09-01T16:00:00.014-05:00

As I look forward to cooler weather I've starting to think about 80 meters. With the winter months 80 becomes quieter and a better band for "DX". 80 is also to best band for my 1929 transmitters. I'd like to put up a better 80 meter antenna. Right now my endfed wire is only 10'-15' off the ground. If works OK for Minnesota but not much else beyond that. The radiation angle is too high. My backyard was too recently a corn field. Nothing back there is tall enough to support a higher dipole or end fed wire.

I'm going to start with a 30' to 35' 80 meter center loaded vertical and maybe even top load it a little. For a mast I'm going to try some of the fiberglass camouflage netting support poles / antenna masts seen on ebay these days. AI4WM has a good article on the web describing these poles . I found some with the fiberglass reinforcing ring on ebay fairly cheap. A trip to my local big box hardware store resulted in several "attachments pictured:

1.5" Conduit Hanger - This allows me to attach coils, pulleys, etc to a mast or they can be used to attach to mast to something else (like a fence or a post).

1.25" PVC Cross - This fits nicely over the top/male end of the mast.

2" x 1.5" PVC Reducer - This I found in the electrical department. With a little drilling to add a few wire loops I should be able to use this to attach guys

1.25" PVC Plug - This goes in the top (when mounted) arm of the PVC cross. It will give me a place to add a 6' whip above the top fiberglass mast.

More C-Pole Vertical Array

2010-08-23T19:23:00.006-05:00

After building/using my two C-Pole array I'm starting to rethink my plan.

KF2YN's C-Pole vertical array design calls for dedicated C-Poles (each pruned to have a 25 ohm input impedance) and phasing lines that both transform the antenna impedance to 100 ohms and set the phase delay between the two antennas. On the surface this looks doable but I've a lot of concern about getting the phasing lines right. W8WWV's measurements showed about a 4% delta as he measured the electrical length of a 17.1' long piece of coax. Also, I don't want to dedicate two C-Poles to an antenna that I won't be using much.

A local friend of mine wants to build a self supporting C-Pole antenna like mine. I can feed two verticals with arbitrary (but equal) lengths of coax and a simple Tee connector at the antenna tuner to make up for the 25 ohm combined feed impedance...no need to worry about electrical lengths. In addition, self supporting antennas can be positioned anywhere to point my signal where I want it to go that day. I can even boost the gain a little (up to 4.8 dB) by separating the antennas 5/8 wavelength.

It's still August, I should have another couple of months of outside weather here in Minnesota.

A Two C-Pole Steerable Array

2010-08-11T16:15:00.019-05:00

Yesterday I finally got my two C-Pole phased array up and on the air. In fact, after tuning it a little I easily made two QRP contacts, one with N2UGB in NY and the other with CT4RL/1 in Portugal.

My journey from idea to an antenna was based on Chapter 13.3, "A Steerable C-Pole Array" in Brian Cake's book, "Antenna Designer's Notebook". Here Brian presented a design based on phased array theory and modeling. Brian was not aware of anyone that had actually built one.

The C-Poles themselves are made from Radio Shack 18 gauge stranded hookup wire. 1/2" PVC pipe is used for the top and bottom 40" spreaders. For easy supporting, the two C-Poles are in the same plane and aligned with the rope joining the two antennas. The upper inside corners of the antennas are connected by a 33.5' length of rope. This insures correct spacing. Support ropes are tied to the two top outside corners. Instead of a relay I used a coax T connector. L3 was added/removed as needed to change the radiation pattern.

Without L3 the array is endfire and, according to Brian's modeling, good for 1.18dBi gain. By adding L3 into the short/L2 side both sides become 3/4 wavelength long and the array has 3.5 dBi gain broadside.

I learned a little along the way about...

Baluns and phasing lines...The phasing lengths include the phase delay introduced by the required choke baluns. I had planned to use air core baluns consisting of RG-8X wound around 4" plastic coffee "cans". What I found was that each balun takes about 1/4 wavelength (electrically) of coax. By the time I added the baluns to L1 and L2 in the accompanying diagram I couldn't separate the antenna by a physical half wave. I was forced to use more expensive ferrite toroid baluns that require less coax.
Adding/removing L3...The switch/relay proposed by Brian in his design introduced its own challenges. The relay/switch is part of the phasing network. I found that my DPDT toggle switch with the needed connectors introduced more phase delay to the point that I was again in trouble with the physical separation of the two antennas. I eventually used a T connector instead.
Supports...Finding trees with the right separation, orientation, height and limb placement can be a problem...especially for a temporary installation in the park.
Measuring the electrical length of coax...My MFJ Antenna Analyzer gave a broad X=0 reading. My grip dip meter gave a sharp dip but not on the same frequency as the MFJ (The ARRL Antenna Book recommends against using a dip meter). Eventually I averaged the two MFJ endpoint/X=0 readings to get a center/single frequency and then calculated the coax electrical length based on that frequency.
Gain...1 to 3.5 dBi of gain is hard to notice when asking for signal strength comparisons under real band conditions.

This antenna array may be a good alternative for someone with properly located supports but my typical picnic table operating style doesn't always allow that. This was as interesting exercise but I'll probably keep using my single C-Pole when I'm at the park.

QRP operating at Myre-Big Lake State Park

2010-07-27T09:42:00.011-05:00

This last weekend Beth and I took our camper trailer to Myre-Big Lake State Park near Albert Lea, MN. I had along my K1 and Crappie Pole 20 mtr C-Pole vertical.

As expected the C-Pole antenna worked well. Over the weekend I had 11 contacts including WA3SLN (PA), K4SPO (KY), K3WWP (PA), AF4O (TN), WB2PEF (NY), VA3RKM (ONT), WB6OJB (CA),WB4KLI (KY), WD9F (IL), W2IQK (NY) and W9LD (WA). I also started a QSO with AB7KT (NV) but that QSO was as victim of QSB/QRM/QRN.

Charles, K1ETU, from Oneonta, NY, spotted me and stopped by for an enjoyable "eyeball QSO". Bill, a camper from Louisville, KY, also stopped by bringing his two sons. Bill has been interested in ham radio since a teenager but had never gotten a license. Now he's thinking of locating a Louisville Radio Club and working on getting his ticket.

The crappie pole frame for my C-Pole really stands out in a campground. It looks like some sort of tall skinny game target or goal. Lots of campers noticed it as they walked or drove by, some asked about it. My favorite comment: "I've never seen a camping accessory like that before".

More W0VLZ Operating

2010-06-24T20:01:00.006-05:00

Strong signals are few and far between here at the Shady Creek Resort but I'm still been able to make contacts using my K1 running five watts into my Crappie Pole C-Pole antenna.

My surprise contact yesterday was EA6UN on the Balearic Islands off the coast of Spain in the western Mediterranean Sea. That's over 4600 miles on my five watts. I found Jurek calling CQ on 14.050 MHz with no responses. He came right back to me and gave a 579 report. Today's QSOs have all been to the west...WB6HGJ (CA), W7LPV (AZ) and N6IV (CA).

W0VLZ Operating

2010-06-22T22:17:00.009-05:00

I have almost a week to kick back at a lake resort here in north central Minnesota. As usual I have my K1 along. In the past I would have made use of a tree as an antenna support for my end fed 67' wire antenna. This time I'm using my Crappie Pole C-Pole antenna.

Conditions have been marginal at best with strong signals few and far between and QSB the order of the day. Daily operating has been rewarded by a few contacts....VE3FIT (Toronto, ON), N3EIN (Coatesville, PA) and
W9FHA (Evansville, IN). Another contact, with K9WWT in Merrillville, IN, was a victim of QSB. My signal went from 589 to unreadable in the length of George's initial transmission.

The Mitey Mite Beginner Transceiver

2010-06-10T13:08:00.022-05:00

Last weekend I attended the TwinsLAN/3M swapmeet in St Paul, MN. This is always one of my favorite swapmeets of the year. It is open-air in a large parking lot so all of the boatanchors show up that we don't want to lug inside to a table...just throw open the van doors or uncover the pickup bed and sell.This year I saw many more boat Nationals, Hallicrafters, Johnsons and Heathkits than I've seen in the past...it was a great meet.

One item caught my attention, a late 40's United Surplus Materials "Mity Mite" HF radio. It is a three tube regenerative receiver/transmitter. The audio stage of the two tube receiver doubles as a single tube crystal controlled oscillator/transmitter. The third tube is a rectifier. I bought it from KB0DVM. He built and used this little rig while he was an Ag student at U of Wisconsin/Madison in 1948.

This is a great example of a minimal design making use of available WWII surplus parts. The first steps in the instruction manual explain how the disassemble the included BC-745 pogo stick transceiver tuning unit to get the crystal, two sockets, a tuning coil and the bandset capacitor. The design itself would not make it off of today's drawing boards. First it is an AC-DC set with one side of the AC line connected directly to the metal chassis/cabinet...what a shocker! A safer (and more expensive) AC-DC design has circuit ground isolated from the chassis but not this one. A quick look at the operating instructions shows a note about not connecting an antenna ground but nothing about the shock hazard. Next there is no tuned circuit in the transmitter output. Any harmonics generated by the crystal oscillator are passed unattenuated to the antenna. Again not a good design but it works, though on several bands at the same time.

The Mity Mite is a pretty neat little radio that reflects the time and market it was designed for. It is a keeper. I'll probably figure out a way to put it on the air (while staying on one band and not killing myself).

A C-Pole Antenna for QRPxpeditions

2010-05-31T21:18:00.020-05:00

I've finished yet one more version of my Crappie Pole antenna, this one based on KF2YN's ground independent vertical antenna (or C-Pole). See here and April 2004 QST, page 37, for more information. After trimming it a little it measures 1:1 at 14.060 MHz rising to 2.5:1 at 14.35MHz and 1.2:1 at 14.0MHz.

I found the choke balun to be key to making this antenna work. With no choke the SWR was over 14:1 at 14.060MHz and with a 10 ferrite bead choke the SWR was still 2.8:1 at 14.060MHz. What I'm using now is 15 turns of RG8X single layer wound on a 4" plastic coffee can.

This antenna is about 18' tall, self supporting without guys and has only a 4' x 5' footprint. It breaks down to a bundle 5' long. Physically it looks like a tall skinny goal post. Add a birdie and two racquets and it should fit well into a typical camping weekend.

View a video of me setting up this antenna at http://www.youtube.com/watch?v=nYn-GnwcSoE

Today I made several nice contacts using my K1 at 5 watts and this antenna including W8CQU in Ohio (599), WA3SLN in Pennsylvania (449), W0WCA in Colorado (449), KI0II in Colorado (549) and N4ESS in Florida (579).

This antenna is going with us when we go camping this summer. Thank you KF2YN.

Update: On June 23 I worked EA6UN on the Balearic Islands off the coast of Spain in the western Mediterranean Sea. That's over 4600 miles on my five watts and this antenna. I found Jurek calling CQ on 14.050 MHz with no responses. He came right back to me and gave a 579 report.

An SW-4 Mystery

2010-05-24T22:46:00.007-05:00

A friend of mine noticed that my National SW-4 shown at http://www.prismnet.com/~nielw/nat_list/sw4.htm uses what looks like standard SW3 type audios as opposed to the National "Duo Coupler" mentioned in the SW-4 ad. Other National radios show a production process that used parts that were available. Close inspection and comparisons between National receivers of the same model can show undocumented differences in details. Are this audios replacement parts or do they reflect a production change to take advantage of existing stock?

As I looked at these audios I saw something else. Close inspection of my SW-4 bakelite chassis showed three large plugged holes and several plugged small bolt holes. Parts mounting and the quality of the work makes it appear that all of this chassis rework was done before most of the parts were mounted. Why all of the extra plugged holes? Was the chassis originally drilled for another product and then reworked? Was the chassis made from a piece of bakelite that already had a few holes in it? Did a worker make several errors that had to be fixed before the chassis could be used?

There are a few SW-4s still around. I wonder, do they show similar changes and reworks? Were these sorts of production techniques common or is this really a set that was carefully reworked at some point after it left the factory?

A 20 Meter Crappie Pole Vertical

2010-05-17T15:49:00.008-05:00

This past weekend we had nice weather here in southern Minnesota....mostly sunny and temperatures around 70. I spent some time working on a new portable antenna and then using it on the air.

I was looking for something simpler than my 20 Meter Crappie Pole Vee dipole. I decided to try a quarter wavelength vertical. The March 2010 issue of QST has a good article on ground systems for vertical HF antennas. Based on that I concluded that a 1/4 wave length vertical with only 4 elevated resonant radials should perform fairly well. What I ended up with is a 16 1/2' crappie pole on top of a 4' base section. The crappie pole itself is non-conductive fiberglass. It serves only as a support for the vertical wire. The guys at the top of the base section are 14 gauge stranded copper wire. These are trimmed to resonate on 14.05 MHz and serve as antenna radials sloping from 4' at the base of the vertical to about 1' were they are each tied off with adjustable lines.

On Saturday while using this antenna and my K1 I worked WA0FJT in Independence, MO on 14.050. There was some QSB but our 5 watt CW signals were usually 589 both ways. I got on the air again on Sunday afternoon and worked WB4YXD (New Mexico), N4HUS (Arizona), W2LG (Florida) and KB2DHG (New York). All came back to my CQs on a fairly quiet/vacant band. Via email I even received a reception report from W1CTT (Maine).

The antenna seems to be fairly effective but the elevated 16' radials could be a problem, especially in a full campground or picnic area. I'll look some more for a 20 meter self supporting antenna that fits better into an average campsite

More TZ-20 Amplifier

2010-05-02T17:21:00.002-05:00

Work continues....

More TZ-20 Amplifier

2010-04-19T16:49:00.007-05:00

With the chassis and front panel drilled, punched and painted this project should start looking more like a kit. Everything is in hand, all I need to do is mount, wire and solder.

I laid out the chassis and front panel so that eventually this amplifier will serve as an upper deck of a 70 watt CW transmitter. My 1934 transmitter will be the lower deck/driver.

Springtime - QRPtime

2010-04-13T08:10:00.007-05:00

With an early spring here in SE Minnesota I can start thinking about QRP again. One of my favorite local picnic table QRP spots here in Rochester is Essex Park. It has plenty of space, lots of trees with limbs about right for antenna supports and movable picnic tables. Take a look here for a video on my operating from Essex park. On Saturday I worked N1LU, Don in NH, and K1TG, Roger in CT. K1TG was an especially good QSO. We are both active in the AWA and have worked each other using our vintage stations.

This weekend at Essex Park I also worked on a new antenna. My end fed half wave and full wave wire antennas do a fine job but they require at least one well placed tree. I could use a self supporting antenna. Cabellas (and other big box sporting goods stores) sell a 16.5' collapsible crappie (as in fishing) pole. 16.5' is just about right for half of a 20 meter dipole. On Sunday I setup two of these poles to form a V to support a V (not inverted V) dipole. Read more about this antenna here. It appears to work as well as a straight dipole and it is fairly portable....now I need to find a bare nob of a hill to operate from.

National TRM 56 MC Transceiver

2010-03-27T18:27:00.006-05:00

Last week I acquired a 30's vintage National 56 MC transceiver. Read about this model on my web site at http://www.prismnet.com/~nielw/TRM_TRW/TRMpage.htm . The TRM and the wooden cased TRW were two of the first commercially available VHF radios. At only 6"x6"x7.5" and 8.5 pounds it is amazingly heavy for it's size. The two special National transformers add a lot to the weight.

I don't find much information about the TRM. What I've found is from National's 1935 catalog and a 1933 article that, while it doesn't mention it by name, appears to describe the TRM. None of my catalogs mention the TRM or TRW after 1935 but my TRM has a model tag. National didn't but tags on their equipment until after James Millen left in 1938. This one must be a late model.

Another Swapmeet Find

2010-03-18T16:07:00.005-05:00

Here's something that I keep around to show visitors that hams really did build the transmitters described in QST. Take a look at my version of George Grammer's push-pull TNT transmitter. This one here is a lot worse for wear but it is recognizable.

Swapmeet Find

2010-03-10T21:48:00.007-06:00

Every once and a while over the years I've picked an item at a swapmeet just because it was interesting and if it could talk would have a story to share.

Here's one. I don't remember when or where I got it but probably at a central Texas swapmeet a few years ago. Some one on a budget wanted to get into ham radio. The local trash heap contributed an old crystal set complete with loose coupler. The tuning coil was rewound as the antenna transformer primary. Some tuning was allowed by striping off insulation in a few places. The loose coupler became the antenna coil and allowed variable coupling. I found a section of the Sunday comics shoved into the loose coupler to keep it in place..date1930. Two of the holes on the board next to the spark coil match the mounting holes for a Bunnell telegraph key.

More RF Amp

2010-03-05T15:49:00.010-06:00

A push-pull amplifier is two tuning caps, two coils and two tubes right? With all of the support circuitry, the output loading circuit I like and miscellaneous parts and hardware it is starting to look like a real project. Once the drilling is done this one will sit until warm weather returns to Minnesota (maybe May?). I want to paint the chassis but not with snow on the ground and temperatures in the 30s.

RF Amp

2010-02-21T23:25:00.008-06:00

Most of my 30s vintage transmitters are in the 10-20 watt range. It would be fun to have a little more power, especially with my 10 watt Meissner Signal Shifter / VFO. According to the specs two Taylor TZ20s in push-pull can be driven with 5 watts to about 110 watts input or 85 watt output. This sounds like what I'm looking for.

As usual any project starts with sorting through parts and then doing a preliminary layout before taking a drill to the metal.

1929 and 1930 Stations

2010-02-05T09:31:00.003-06:00

Lots of times questions get asked about what sort of rig to put on the air as a 1929 station. What were hams really using? Do the back page ads in QST really reflect what was on the air?

As I went through my old issues of the AWA OTB/Journal I found Bruce Kelley's comments on 1929 equipment in the May 1994 issue. He summarized 1929 and 1930 QSL card information from W1NE. He saw that Hartley oscillators and the 210 dominated the transmitter scene and almost 90% of the receivers had no RF stage. I found two 1930 QSL cards in my collection and added those to Bruce's tabulation. I've posted this data at http://www.prismnet.com/~nielw/OldQSLCardInfo2.pdf .

If you have similar 1929 or 1930 QSL data email it to me and I'll add it to the summary.

AWA Linc Cundall Memorial OT CW Contest

2010-01-25T07:39:00.009-06:00

For two days this past week I participated in the AWA Linc Cundall Memorial OT CW Contest. This contest gives a significant multiplier to those using pre 1947 gear. I used a National NC-101X and one of my recent homebrew transmitters, a "46 job". I worked nine stations in four states plus Ontario.

Photo QSL Cards

2010-01-02T13:40:00.015-06:00

QSL cards are a ham radio tradition that I was introduced to when I was a novice in 1966. My novice card then was a fairly generic design ordered 100 cards at a time from the Little Print Shop near Austin, Texas.

These days I usually custom create my QSL cards to go with a particular event or location. Lots of places will print digital photos and most allow on-line submission. I've seen prices as low as 9 cents per print with no minimum. All that is needed is a jpg file the right size.

Start with your favorite graphics editor, even Microsoft Paint has enough power and function to do the job.

First create a blank colored background with the right aspect ratio to match the prints to be ordered. I planned to order 4" x 6" prints so I created a 800 x 1200 pixel background. This background gives you control over auto resize/crop that occurs when your file is printed. The color doesn't matter. It will eventually get trimmed off.

Use your editor to cut out from the middle of the background a rectangle the matches the final size of the QSL card. For a typical 3.5" x 5.5" QSL card on a 800 x 1200 pixel background this rectangle will be 700 x 1050 pixels. This space is where you create your QSL card.

Use your graphics editor to add whatever QSL card text and images you wish. For Microsoft Paint I found it best to crop and resize any photos or images before I paste them into the QSL card.

Send the jpg file off to be printed.

The resulting 4" x 6" print will have a colored frame that needs to be trimmed off. This should leave your 3.5" x 5.5" QSL card. A paper cutter works great for trimming.

Other cheaper options may be available but for the QSL card information I use a Avery #5264 3.25" x 4" shipping label stuck to the back of the QSL card. Inside the Avery box are instructions telling how to use a template included in Microsoft Word to create six preprinted labels per sheet of shipping labels.

1928 Hartley / AWA 1929 B Kelley QSO Party

2009-12-13T22:12:00.013-06:00

The past two weekends gave me a chance to get some more operating time on my 1928 Hartley transmitter. These were the weekends of the AWA Bruce Kelley Memorial 1929 QSO Party . The first weekend I used my HRO Sr with the Hartley. On the second weekend I paired my Drake 2B with my Hartley. I had a good time working other '29 transmitters in Minnesota, Wisconsin, Illinois, New Hampshire, North Carolina, Ohio, Ontario and British Columbia.

In total I made 16 contacts and learned a little about the limitations of my station. First, I really need a higher antenna. My antenna is a 105' inverted "L" only about 10' to 20' off the ground. It loads up nicely but, given this low height, has a fairly high angle of radiation. It probably qualifies as a Near Ver tical Incident Skywave (NVIS) Antenna. Out of my first six contacts, five were here in Minnesota and most of them reported a strong signal. I also found that the best time was late afternoon, not the night time hours. The first weekend the only QSO I had outside of MN was with Ohio and it was when the QSO Party rules allowed me to crank the power up a little. When the propagation changes my antenna works OK but I feel it does limit me. Next, I learned that 40 meter transmitter performance is a little down from 80. While I've received a good signal report on 40, I can't get as much power out and I had more trouble getting on frequency. My Hartley is a usable 40 meter transmitter but 80 is definitely its better band.

1928 Transmitter Tuning

2009-11-16T09:10:00.004-06:00

Ross Hull's QST article documents a lot of experimentation done to understand the behavior of self-excited oscillators. Whether Hartley, Colpitts, TPTG or TNT Hull concluded that all of them behave about the same and the same tuning guidelines apply to all of them. In summary, any self-excited oscillator should be run at only about half power in order to produce at acceptable signal.

After the transmitter is on frequency and running at full plate voltage:

1) Tighten the antenna coupling as much as possible. In the case of my transmitter this meant moving the antenna coil until it almost touched the tuning coil. At maximum antenna coupling tune antenna loading for maximum output and note this "maximum output".

2) Back off antenna coupling to 75% maximum power (watts) or 85% output current (RF Amps) retuning antenna loading along the way.

3) Once you are at 75% power (or 85% RF current) output, detune antenna loading by adding capacitance to reduce output another 75% power (or 85% RF current). After detuning check your signal. In some cases Hull found that detuning antenna loading worked best if capacitance was reduced rather than added.

Hull plotted frequency vs load capacitance. His curves show a fairly steep curve around resonance and then they flatten out. When a self-excited oscillator is peaked up for maximum output any changes in antenna loading will have a maximum impact on frequency. At this tuneup point an antenna swaying in the wind (changing the load that the transmitter sees) will have a maximum impact on the signal frequency. Detuning the output the oscillator away from peak output moves the operating point to the flatter part of the frequency vs load capacitance curve. Antenna sway will have less impact.

1928 Transmitter Signal Quality

2009-11-15T09:52:00.012-06:00

Ross Hull's August 1928 QST article, "Overhauling the Transmitter for 1929", is a great article for anyone interested in putting a late 20s/early 30s self excited oscillator on the air. This includes the Hartley, Colpitts, TPTG and TNT transmitters used in the AWA Bruce Kelly 1929 CW Party. In the words of QST, this "is, we feel, one of the most important articles ever published for the radio amateur. Let every amateur study it most carefully, and apply its information, for it contains salvation for 1929." It can be found by searching the QST magazine article archives at http://www.arrl.org/.

Ross Hull's major point is that the poor signals legal in 1928 will no longer be acceptable in 1929. He further states that the main problem is the "men pushing the keys". How 1929 transmitters are tuned up makes a big difference in signal quality. The actual transmitter required to meet 1929 standards can be fairly simple. To prove his point he describes the one I built, a "simple -- in fact crude -- rig...capable of performing quite creditably". He even goes on to say that he anticipates some "raspberries" over the crudity of his simple transmitter.

Transmitter features helping signal quality include a heavy tank coil/circuit, mounting the tube so tuned circuit heating is minimized and high tuning capacity/low inductance. Ross Hull emphasizes that the inexpensive hardware features he's listed combined with proper tuning over come lots of the frequency shift introduced by marginally filtered or unregulated B+ supplies, antennas swaying in the wind and components heating up. Simple 1929 transmitters don't need to "splutter, wobble, creep and rattle across great slices of the bands".

In fairness, I still find that moderate winds causing antenna sway does introduce some FMing, but my signal is acceptable. Hull, in fact, states that a DC (T9) note is extremely uncommon and rather unpleasant. He much prefers a more "musical note" that we might rate T8. Given proper tuning that's about where mine is: a sweet, musical, T8 signal. Also keep in mind that this transmitter design does not address other "creature comforts". It is microphonic requiring it to be placed on a table separate from the operating position, hand capacity is a problem and bandspread, such that there is, is barely adequate for getting on frequency. These could be addressed in a more expensive design but their solution is not required in order to archive "any reasonable [signal quality] standard set for 1929".

1928 Hartley Coils

2009-11-13T14:34:00.010-06:00

Pictured are my 80 and 40 meter tank coils. Ross Hull made a strong point in his QST article that these coils need to be able to handle a lot of current (5 amps of RF for this design), be mechanically stable and tune with as much capacitance as possible.

These coils were wound out of 1/4" OD copper tubing. A piece of 2 3/8" OD pipe was used for a winding form. Once a coil was wound I installed it and then adjusted the turn spacing so that the bottom edge of each band fell close to maximum tank tuning capacity.

While shopping for copper tubing I found that tubing wall thickness varied brand to brand. For best current handling and mechanical stability I bought the heaviest/thickest I could find.

More 1928 Hartley

2009-11-06T15:35:00.018-06:00

The last few evenings have included some final cleanup of the Hartley and then getting it on the air some more. There's been several of us on 80 meters around 3615 during the late evening but the 80 mtr propagation god hasn't smiled on me since my QSO with VE3AWA. Some of the others have heard me but I haven't worked anyone. Here is how I sounded last night at VE7SL's QTH in British Columbia:

More 1928 Hartley

2009-10-30T21:27:00.018-05:00

Well, it's in the log...the first QSO. Tonight I worked Lou, VE3AWA, on 3565. We were 549-559 both ways and had a nice contact going until 80 meter QRM caught up with us. Lou was using his Push-Pull TPTG transmitter with a NC101X. I had my HRO Sr paired with the Hartley running 10 watts input and about 3 watts out.

For this contact I added an extension to the main tuning capacitor shaft. Both my TNT and this Hartley are really sensitive to hand capacity. Adding 8" to the tuning shaft helped a lot as I moved onto frequency. I also used a VT-25, the military version of the type 10.

Not obvious in the Hartley list of parts are the National Velvet Vernier dials used by Ross Hull. These make a big difference adding mechanical bandspread to help overcome the 80 meter CW band being crammed into a few degrees of capacitor rotation at one end of its travel.

Lou asked how come my signal was so stable. Antennas swinging in the wind typically shift the transmitter frequency as the load changes. My 105' inverted "L" happens to be a little low (only 10-20' off the ground) and behind a ridge so it is protected from the west winds. I also run with the antenna loosely coupled to the transmitter. Output is only about three watts instead of the 5-6 watts the transmitter is capable of at maximum coupling.

The RF choke is now one I hand wound on a 3/4" piece of wooden rod like Ross Hull's original 1928 design. It doesn't have quite as many turns as he called for but it works fine.

More 1928 Hartley

2009-10-21T12:48:00.006-05:00

After a little debugging it works!

When I first put power to my version of Ross Hull's Hartley transmitter I could only get it to oscillate if the cathode clip is either not attached at all or clipped to the tank coil near the plate (rather than grid) end. RF with the clip this high on the tank coil is detectable on a nearby receiver but not measurable at the transmitter antenna.

It turned out that all things that look like RF chokes don't make good RF chokes. Mine from my junque box looked like a single layer vintage RF choke, it tested good for continuity and B+ showed up at the tube socket but didn't work well in this circuit. Replacing it with a
more modern RF choke fixed my problem. I'll need to go back and hand wind one like shown in the original 1928 QST article.

I also needed a 4:1 balun to match well to a 50 ohm load.

Now with 300 V B+ and about 25mA input I can push it to over three watts out. Backing off gives me a clean 2 watts out.

Thank you to several AWA friends that helped with parts and advice.

More 1928 Hartley

2009-10-19T16:07:00.007-05:00

Except for a couple of coil clips my clone of Ross Hull's 1928 Hartley is complete. It's ready for power and checkout.

More 1928 Hartley

2009-10-15T21:31:00.006-05:00

Today we have surface-mount-technology, before that we had pin-in-hole printed circuit cards, before that point-to-point wiring and before that we had breadboards. With breadboard construction came solid bus bar wiring. Bus bar is stiff enough that wiring takes on a 3D sort of aspect. Wiring of a transmitter such as this Hartley has height along with depth and width.

More 1928 Hartley

2009-10-14T20:35:00.009-05:00

Working through this project has given me a new appreciation of the homebrewing skills of many of the hams during the twenties and thirties. The article on this particular transmitter has some gaps in the construction details....for coil turn information the builder is referred to the coil photo, to count the turns himself....and....Keying method is a reference to another chapter and, again, left to the builder to figure out.

I chose cathode keying for my version. I also buried the cathode resistors under the tuning capacitor. Keying added two additional Fahnestock clips along the left hand side. From the front mine lays out as keying (hot side), keying (ground side), filament, filament, B-/ground and B+.

More 1928 Hartley

2009-10-13T16:56:00.005-05:00

That pile of old parts, wood and copper tubing is starting to look like a transmitter. The eight parts left are mostly to be wired into place so things should speed up a little.

The unsung hero of any project like this is a drill press. Without one you could never get all of the holes right.

More 1928 Hartley

2009-10-02T21:53:00.002-05:00

With (plexi)glass rods ordered and one additional National DX capacitor in the mail from a friend the next step is some table saw time.

A 1928 Hartley

2009-09-29T23:42:00.011-05:00

After seeing my 1934 transmitter a friend asked if I was doing anything special for the Bruce Kelley Memorial 1929 QSO Party coming up in December. Last year I put my TNT transmitter and SW3 on the air. This year it might be interesting to try a Hartley oscillator.

As ham radio approached January 1, 1929, and the more rigorous standards, the ARRL encouraged hams to improve their stations. One improved transmitter design was a single tube Hartley oscillator described by Ross Hull in the August 1928 issue of QST. Bruce Howes, W1UJR, covers this design on his web site here.

I've been searching through my junque box looking for the parts I need. The first step was a parts list and an enlarged scan/photo of the transmitter. After picking through multiple boxes and peanut butter jars I've lots of possibilities. Now it's a matter of sorting through what I have for the parts that match the original design.

Camping and Picnic Table QRP

2009-09-27T20:07:00.004-05:00

This last weekend we planned a campout at Frontenac State Park. We've picniced there several times but have never camped over night. No camping trip packing list is complete without my K1. (This time we did forget the blankets and pillows but the K1 was loaded.)

I ended up getting several chances to ham. After a quick listen on 20 and discovering the CQ WW RTTY contest in full swing I moved to 30 mtrs for the weekend. The antenna was a 45' endfed wire (1/2 length wave on 30 mtrs) in a tree next to the campsite. It was approximately broadside to the NNE but did a great job into the northeast US. Between Saturday and Sunday I worked W3XAF (MD), KB3TJS (MD), W0IMD (CO), AA3TH (PA), WA1IIE (ME) and KD3DK (PA).

More 1934 Transmitter

2009-09-22T20:27:00.008-05:00

Remember the safety problem with my 1934 transmitter? One of the phone plugs is for metering and the other is for the key. If, in the heat of the moment, I get the two mixed up and plug the key into a B+ metering jack, I'll have over 300 volts on the key.

To protect myself I tied a length of string and a plastic cable clamp to the key phone plug (any lump of plastic would work). After the key is plugged in I slide the cable clamp under the front edge of the transmitter. The string is short enough that the plug can not be removed without getting the clamp out from under the transmitter.

A 1934 transmitter - On the Air

2009-09-16T10:55:00.008-05:00

Yesterday I set up my 1934 transmitter up with my NC101X and tried the pair out on 80 meters using my endfed 105' inverted "L" antenna only about 10'-20' off the ground. The station worked fine.

At 21:45 I had a nice QSO on 3570 with NG9D in Plainfield, IL. Lynn's signal varied from 589 to 599+. He reported that my 589 signal sounded fine/stable.

Also shown in the picture is my iambic keyer set up to key older tube rigs.

More 1934 transmitter - It Works!

2009-09-13T22:54:00.023-05:00

I've finished wiring my 1934 transmitter, powered it up and it works! With about 300 volts on the plates of the 46s and the 47 it loads to 15-20 watts input and 7-10 watts output. It sounds great also.

One change I made from the Bill Orr design is to connect the 47 screen to regulated 150V rather than a resistor network off of B+.

This transmitter is not without some personality, though. Only the amplifier stage is keyed so the oscillator stage runs continuously. On key up any energy from the oscillator that makes it to the antenna will be heard as a faint back wave. We'll see if this is objectionable. The second personality trait is, unfortunately, pretty nasty. When using the rig, one phone plug is for metering and a second is for the key. If in the heat of the moment I get the two mixed up and plug the key into a metering jack I'll have over 300 volts on my key. To make matters even worse, keying the metering/B+ line works so I may not even be aware that I have the plugs swapped until I get myself between the key and ground. I'm planning something that will keep me from accidentally removing the key plug.

Eventually I plan is to mate this transmitter with my National FB7X for a complete 1934 station that I'll use in the 2010 AWA Linc Cundall OT CW Contest.

QRP Operating at Crater Lake National Park

2009-08-28T20:53:00.007-05:00

After three weeks, 5300 miles and 12 western states Beth and I are back in Rochester. I took along my K1 in a lunch bag so that I'd be ready for any ham opportunities.

One of our tourist stops was Crater Lake in southeastern Oregon. On August 19 I found a tree stump overlooking the lake, threw a 32' length of wire into a nearby tree and got on 20 meters. My location was on the western rim of the 5 mile wide caldera with the water around 800' below me. After a few CQs I worked Jim, W0CML, near Denver. Once he swung his beam around he was nice copy at 589 and I was 579. After supper that evening I operated on 40 from in front of our cabin at Mazama Village, 7 miles and about 1000' below the rim. Tim, AD7AN, in San Diego gave me a 529 while he was 579 for me.

"Picnic table QRP" continues to be a fun way to spend some spare time while traveling.

More 1934 Transmitter

2009-07-09T06:44:00.007-05:00

I've gotten the components all mounted and the transmitter is ready for wiring. I learned a few things along the way...

30s vintage Sangamo mica capacitors are large enough that they don't mount well on their own leads. Each one must be mechanically supported, either by a solder strip or by screwing to the wooden sides of the chassis.

The wooden chassis takes 1 1/2 inches of available length and width. This can impact the layout. Using an all metal chassis there is space for a buffer stage between the oscillator and amplifier. With 1 1/2 taken off the length/width plus the added reinforcing across the middle it would be a challenge to fit the buffer stage in there.

Will the lead length be a problem? Certainly I wouldn't trust this spread out layout at 30MHz but it may be OK on 7MHz. Time will tell.

QRP from Frontenac State Park

2009-07-06T19:15:00.014-05:00

Sunday afternoon, July 5, I got over to Frontenac State Park for some picnic table QRP. The picnic area there sits at the edge of a 400' bluff over looking the Mississippi River. Below the park is Lake Pepin , a naturally wide part of the upper Mississippi. To the east, across the Mississippi/Lake Pepin, is Wisconsin. The weather Sunday was sunny but not too warm in the shade, perfect for picnic table QRP.

Using my K1 running 4 watts and feeding a 67' end fed wire I worked K4BAI(Columbus, GA), WA3PAK(Marion, OH) and N7JOX(northern CO near Cheyenne, WY). All in all a satisfying and relaxing afternoon....

More 1934 Transmitter

2009-05-31T22:33:00.010-05:00

After some quality table saw time, a bunch of drill press time and eight coats of paint (primer coat, satin black, three coats of wrinkle paint that didn't wrinkle and three more coats that did) I have a wood and aluminum chassis that looks pretty good. The layout is much like the Gross CW-25 but without the buffer stage. In place of the middle/buffer tuning dial I'm mounting a plate current meter. Across the bottom are three 1/4" phone jacks. One is the key jack. The other two are in the B+ circuits of the oscillator and final amp stages. These two jacks will have 350VDC exposed on the outside rim. For safety I recessed these jacks 1/2" behind the front panel. I also added a B+ switch on the far right.

I found two more examples of this tube lineup. One is a George Grammer construction project covered in November 1932 and February 1933 QST. The second is the Collins 4A transmitter.

More 1934 Transmitter

2009-04-10T08:12:00.006-05:00

After collecting all of the parts comes "playing checkers" to find the best layout given the set of parts located. In this case I found suitable 30's parts for all of the major components except the chassis itself. For it I'm using a 17"x10" sheet of 18 gauge aluminum. It will be fastened to a 4 1/2" tall wooden frame and then frame and aluminum painted black winkle.

A 1934 Style Transmitter

2009-04-09T21:30:00.016-05:00

Since the AWA Linc Cundall OT CW Contest in January I've been thinking about building another transmitter, this one falling in between my 1929 TNT transmitter and my Thordarson 100 or late 30's 6L6 transmitters. I want to use it with my National FB-7 so it needs to be an early to mid 30's design.

A popular design in the early 30's used a type 47 as a crystal oscillator driving a buffer and final on 160 through 10 meters. Typical power was anywhere from 20 watts on up depending on the tube lineup. The Gross CW-25 was one example. It had a 47 oscillator driving a 46 buffer/multiplier followed by two 46s in parallel. Plug-in coils were available for all bands 160 - 10. This looks like a pretty neat transmitter. More about the CW-25 can be found in Bill Orr's "Antennas" column in the February 1977 issue of CQ magazine.

I wish I could find a CW-25 available. Does anyone have one they will part with? In the mean time I'll have to homebrew something.

The cover story of the November 1971 issue on CQ magazine is a Bill Orr construction article describing a 160/80/40 meter "1934 Style Transmitter". Circuit-wise it is a close match to the CW-25 but without the buffer/multiplier stage. This circuit design fits my early/mid 30's requirement but the CW-25 chassis sort of construction better matches the "modern" look of my FB-7. I'll combine the two using the circuit from Bill Orr's article but building it to look more like the CW-25.

Notice that the schematic scanned from the original CQ article is missing the connection between the coupling capacitor C6 and the 46 tube grids.

QRP FYBO Contest

2009-02-07T20:28:00.012-06:00

Today I participated in the annual QRP FYBO (Freeze Your B___ Off) contest. See http://www.azscqrpions.org . It happened that we are into a little warm spell after several weeks of below freezing weather. The temperature was 40 at 10AM when I got started, rose to 46 around lunchtime and then dropped into the 30s by the time I got off the air at 3:15. I'm not a big contester. With on and off operating and marginal band conditions I made only 5 contacts on 40 and 20 CW for 800 points. Most hams I worked were relatively warm, only VE3RRP in Ontario was below freezing.

The FYBO Contest did give me a chance to get out of the basement shack. One of the neighbors interrupted a snowman build to find out why I was lounging on my deck in February. Even with temperatures hitting the mid 40s it is still winter in Minnesota.

I found the FYBO Contest a challenging and fun break from my regular winter boatanchor activity. I'll do it again next winter.

AWA Linc Cundall OT CW Contest (Part 2)

2009-01-28T16:54:00.005-06:00

The second half of the AWA Linc Cundall OT CW Contest was this past weekend. Between Saturday evening and Sunday afternoon I added 4 contacts to my log including W0LGU(MN), WA9QNN(WI), WB9WHG(MN) and NG9D(IL). While not a lot of contacts this year my push-pull 6L6 transmitter seemed to work pretty well. I suspect my low antenna (only 10-15ft off the ground) resulted in a lot of RF going straight up. I did OK for nearby stations but heard/worked no east coast stations.

AWA Linc Cundall OT CW Contest

2009-01-23T12:26:00.019-06:00

The first half of the AWA Linc Cundall OT CW Contest ran Wednesday evening through Thursday late afternoon. This coming Saturday is the second half of the "contest".

My station this year is a 1938 vintage NC-101X and a homebrew crystal controlled push-pull 6L6 oscillator. Electrically this transmitter is based on the QSL Push-Pull in QST, June 1940. I added cathode current metering, a load control and regulated the screen voltage to 150V. I ran mine with only 300V on the plates for about 20 watts input and around 10 watts output on 80 and 40. Cosmetically this transmitter is based on what I had on the shelf to work with, an old amplifier build in an even older Meissner Signal Shifter cabinet.

Here in SE Minnesota using my low hung 105' inverted "L" antenna I heard no AWA stations on the air Wednesday night but did work W0NYQ(MN), KB0ROB(MN), VE3AWA(OT) and AA9DH(IL) late Thursday afternoon.

An Iambic keyer rated for cathode keying

2009-01-14T18:01:00.012-06:00

When using my vintage transmitters I've missed not having a keyer. Many older tube transmitters are cathode keyed. The voltage across the key terminals can be high enough to fry the output transistor of a typical modern keyer. In some cases the voltage can even be high enough to be a safety problem.

I already had a K1EL K10 keyer board ( http://k1el.tripod.com/K10.html ). I added a Keyall from Jackson Harbor Press ( http://home.att.net/~jacksonharbor/keyall.htm ) to make a keyer capable of keying up to 500V at 2.A. It works great! I even installed a jack for a straight key so that I use the K10 CW monitor plus the Keyall isolator on Straight Key Night.

1929 AWA QSO Party

2008-12-18T17:33:00.005-06:00

The last two weekends I participated in the AWA 1929 QSO party. The main requirement is that the transmitter be a 1929 or earlier design. I ended up using my two tube TNT (tuned plate - not tuned grid) transmitter (see http://www.io.com/~nielw/tnt/tnt.htm ) while the receiver was a National SW3 three tube regen (see: http://www.io.com/~nielw/nat_list/sw3.htm ). See http://www.io.com/~nielw/1929Stn/1929Station.htm for more information and videos.

I was only on 80 and worked 8 stations, 7 in MN and one, WA3FFC, in PA. MN contacts were W0DGU, K0KCY, W0CWU, WA9WFA, W0NYQ, K0PK AND KB0ROB.

A Simplified CW keying monitor

2008-04-27T19:49:00.008-05:00

My homebrew CW station shown at http://www.io.com/~nielw/2tube_xmtr/2tube_xmtr.htm
includes a control (speaker/power supply/TR switch) box. I found, though, that I still needed some sort of CW monitor. The June 1952 issue of CQ magazine describes a simplified CW keying monitor using only 6 parts. Basically it is a neon bulb type audio oscillator keyed by a second neon bulb energized by transmitter RF. I built the circuit into my control box coupling the monitor output to the grid of the 6F6 audio output stage. I added a 12 Meg resistor from B+ to the junction of the two neon bulbs to help reduce motorboating when the circuit is not energized.

It works fine. Now I can silence the receiver on transmit and have the CW monitor to listen to my own fist.

2008-03-15T10:39:00.005-05:00

As I played with my 6J5/6L6 transmitter I saw that I had some holes in my 80 mtr crystal selection. I had several crystals at 3550 but practically none between 3550 and 3570. Before stable and well calibrated VFOs were plentiful, grinding crystals was a common activity. Military surplus crystals were obtained cheap and ground to the frequency of interest. I decided to grind some of my 3550 KHz crystals up a few KHz to fill in the gaps in my crystal selection.

I used 400 grit wet sandpaper face up on a flat surface as my grinding "station". I removed the quartz crystal plate from the holder and, pressing on two opposite corners, ground in a figure 8 pattern. I'd typically grind for 5 to 10 passes and then rotate 90 degrees, repeating four times. I then cleaned and dried the crystal, reassembled it and checked the frequency. If I hadn't shifted it far enough I repeated the whole process. To insure that I ground only one side of the crystal I marked a side with a dot of ink.

I found that my Millen grid dip oscillator and a frequency counter made a handy crystal checker. I plugged the crystal in place of the GDO coil and capacitively coupled one pin to my frequency counter. The counter then read the crystal frequency and the grid current indicated crystal activity.

Further 6J5/6L6 Transmitter Developments

2008-02-25T20:43:00.025-06:00

Using my 6J5/6L6 transmitter transmitter in the January AWA OT CW Contest reminded me that my original intent for this transmitter was to have some sort of loading control. In theory L2, the output link, can be wound to properly match a 50 ohm load. In reality I never quite got the power I expected when I used a fixed output link. The solution is to switch to a pi network or add a loading capacitor between L2 and ground.

In keeping with the vintage of the design and the typical output networks of the day I added C10, a loading capacitor, between the output link and ground. C10 is actually a 300pf variable with an old television 300pf doorknob capacitor optionally in parallel with it. The photos show a toggle switch next to the output coil that controls whether the extra 300pf is in the circuit of not. It is needed on 80 but not on 40.

Tuneup is now the standard "dip and load " sort of procedure. Plate current is dipped using C8 and then increased by increasing C10 capacitance. This is repeated until adjusting C10 does not increase plate current. The last step should be to dip the plate current using C8. With a 300 volt (under load) power supply mine easily loads up to about 50mA or 15 watts input.

AWA OT CW Contest Operating

2008-01-29T17:00:00.003-06:00

Last week was the AWA OT CW Contest. I had hoped to be operating using my 815 transmitter but it continues to run off on it's own as a tuned grid-tuned plate oscillator. I switched to my 6J5/6L6 transmitter ( http://www.io.com/~nielw/2tube_xmtr/2tube_xmtr.htm ) and a NC-101X ( http://www.io.com/~nielw/nat_list/nc100.htm ). The pair worked well together and I had four enjoyable QSOs including WA9QNN, W0LGU, WU2D and AA4RM.

More on my 6L6/815 Transmitter

2008-01-16T18:02:00.002-06:00

Next Wednesday, January 23, is the AWA Linc Cundall Memorial OT CW Contest. It is about time I get my 6L6/815 Transmitter on the air. Two big stumbling blocks had to be worked on: 1) three different high voltage requirements, 815 B+ around 500 VDC, 815 screen around 250 VDC and oscillator B+ around 150-200 VDC and 2) a tendency of the 815 to run off on it's own as a tuned grid-tuned plate oscillator.

The original transmitter design called for voltage dropping networks to get the right screen and oscillator voltages. In the end I added a VR tube to even out the voltage to the 6L6. In the 1941 design the 6L6 plate voltage would drop from 500 to 250VDC at key down. The oscillator would over drive the 815 as the voltage dropped, creating harmonics and spurious RF output. It was bad enough that the SWR would bounce up at the beginning of each dit or dah indicating RF temporarily not on the design frequency. The VR 150 at the left rear of the chassis along with a 10K resistor network underneath now keeps the oscillator B+ at 150 VDC, key up and key down. I found the 815 screen voltage to be more forgiving than the 6L6 plate voltage. There I added the recommended power resistor network to drop the screen voltage to an acceptable level. Neither of these solutions are elegant. Between them they waste 25 watts of power but they do work.

The instability of the 815 amplifier is still a problem. A tin can (actually Wolf brand chili can) shield around the 815 grid coil helps a lot, especially if the final is lightly loaded. I still have to tune up carefully, though, or the output looks pretty trashy.

BA on 20mtrs

2007-12-20T07:38:00.000-06:00

Tuesday I got on 14.050 cw using one of my boat anchor stations. The station of choice this time was my Collins 75A3 and Central Electronics 20A. In the mid 50s the 20A was one of the first commercially available SSB exciters but it also works fine on CW running about 20 watts. I use mine crystal controlled. Contacts on Dec 18 in the early afternoon included both W5ZR (LA) and NV4I (SC).

AWA 1929 CW Party

2007-12-19T08:00:00.003-06:00

With snow on the picnic tables here in Minnesota my operating has moved from K1/QRP to the boat anchors in the basement. The AWA 1929 CW Party occurred the first two weekends of December. This contest requires that the transmitters reflect 1929 or older technology and tubes. Participation is in the 50 - 100 station range so it is a fairly low key "contest". Even the required log information forces operators to slow down as name, QTH, signal report and transmitter descriptions are exchanged. Power is limited to 10 watts input (except for late east-west QSOs) on 80 and 40 meters. Many of the transmitters are self excited Hartley, TNT or TPTG oscillators link coupled to the antenna. Some are MOPA (master oscillator-power amplifier) two stage transmitters. I put my TNT transmitter on the air with my National NC-81X receiver. Running about 2 watts out on 3560 KHz I had seven enjoyable QSOs. Longest "DX" was N4GJV in Cleveland, NC. All of the others were in MN and WI. The contest was not without some last minute challenges, but not with the 1929 gear. As I got started I realized that I had no way to zero beat my signal. The '81X muting function has no mute bypass switch. With it wired into my T-R relay to mute on transmit I had no way to tune my receiver to listen for my own frequency. Fortunately the '81X is ham band only with relatively good calibration so I wasn't to far off ... but then the NC-81X receiver dial string broke. My receiver could be tuned just fine but I had no direct frequency readout. I made it through the contest by listening for a signal of known frequency and then not straying far from that. It was a fun evening.

More NC-57

2007-11-26T17:18:00.000-06:00

I added a Heathkit QF-1 Q-Multiplier ( http://www.heathkit-museum.com/ham/hvmqf-1.shtml ) to my NC-57. The QF-1 provides additional selectivity or signal rejection as desired. It was marketed by Heathkit starting around 1956 and was a fairly common accessory. It requires a connection to the IF stage plus B+ and filament voltages available at the NC-57 accessory socket.

I found this to be a big help. The QF-1 effectively eliminated the CW audio image (ie. a readable signal each side of zero beat) common in receivers that don't have a crystal filter. Eliminatling the audio image eliminated half the QRM on the band.

NC-57 Project with comments about the NC-125

2007-11-21T09:53:00.000-06:00

For the past few days I've been going through my NC-57. This radio was marketed by National in the late 40s and early 50s. Features include a built-in speaker, electrical bandspread (uncalibrated), regulated B+ for the HF oscillator and a tuned RF stage. Advertised frequency coverage was .54-55MHz. See http://www.io.com/~nielw/nat_list/nc57.htm for more information.

My set had been already gone through by a previous owner, recapped and aligned. This set includes an extra dial string in the bandspread tuning assembly to overcome slipping. While this radio generally worked it also would go dead once and a while for no apparent reason. Close inspection revealed a cracked solder connection on a filament pin of the 6H6 detector. Resoldering this connection fixed the problem.

Properly aligned, the calibration was excellent and sensitivity good but this radio is still only one step removed from a simple SWL receiver. Mechanical and electrical stability is marginal, especially above 40 mtrs. It was no surprise that SSB and CW signals easily overloaded the receiver and BFO. Operation with the BFO requires running the AF gain wide open and controlling volume with the RF gain control. I did like the positive feel of the main tuning. While National used a failure prone dial string for bandspread tuning, main tuning uses a gear/pinch wheel mechanism.

Three years after introducing the NC-57 National came out with the NC-125. Under the covers this "new" receiver was simply a NC-57 with the internal speaker replaced by an S-meter and Select-O-Ject audio filter. Both of these features were available as options on the NC-57. National also replaced the round dials with slide rule dials. Unfortunately National took a step backwards by using slip prone dial strings on both the bandspread and main tuning. The Select-O-Ject feature, while unique, does nothing to remove the audio image. I believe a Q-multiplier similar to the Heathkit QF-1 would have been more useful.

I acquired a tilt base with my NC-57. Besides tilting the radio front for easier reading, this also allows a ham to add extra station controls and some accessories without cluttering up the shack. High on my list is a 1MHz crystal calibrator to help set the main tuning for repeatable bandspread calibration over each ham band.

I plan to use my NC-57 on 80 and 40 with one of my early novice transmitters.

QRP Operating - Austin, TX

2007-10-28T21:48:00.003-05:00

On October 26 I finally had a chance to do some more K1/QRP operating. This time while on a trip to Austin, TX. The weather was great: sunny and about 75. My antenna was again a 67' (full wavelength on 20 mtrs) endfed wire . The operating position was on second floor balcony. I ended up running my antenna up to eaves above me and then sloping down to a fence along side the yard. My clear view was to the east and I was on top of a bluff over looking Lake Travis.

A few minutes before noon I had a QSO started with KC9AWL, Len, in Palm Coast, FL on 14.057. He gave me a 559 but when I noted how deep the QSB/fades were I knew we were in trouble. Len turned it over to me but, evidently, the band went south and he lost me. I never heard him a second time.

Within ten minutes I had another QSO going on 14.057, this time with WA9FZP, Phil, in Racine, WI. This enjoyable QSO lasted about 1/2 hour with 559-569 signals the entire time.

815 Transmitter Postmortem

2007-08-26T22:46:00.000-05:00

After weeks of vacation, etc I finally got back to my 815 transmitter. To recap ... the major mods since the original design shown in the ARRL handbook and my blog entry dated March 19, 2007 have been to 1) add a loading capacitor between one side of the output link and ground 2) Replace R4 with an RFC to a 200-300 VDC supply and 3) replace the 815 screen voltage dropping network R5/R6 with an RFC to a 200-300 VDC supply. The final layout is shown in my May 28 blog entry.

Tests on 40 meters have been a little disappointing. The 815 runs at only 35%-40% effeciency into a 50 ohm load. 50 watts input gives only about 20 watts out. (whoops! I checked my Drake watt meter agains a Bird. Turns out that the Drake watt meter is reading way low. The Bird says I'm putting out about 30 watts. This is about the power output I expected.) Also the transmitter is not real forgiving. If misadjusted, it goes into self oscillation or generates a trashy sounding signal.

This one will go to the back of the shelf. (but after discovering the watt meter error, only while it waits for a power supply)

More QRPxpeditions

2007-07-06T21:43:00.001-05:00

Over the past week I've enjoyed QRPing from both Milwaukee, WI and White Water State Park in SE Minn aboth times using my K1 feeding a 34' endfed wire on on 14.060. In Milwaukee I worked Butch, KD5RSS, in Haskell, OK and Dick, W0NTA near Loveland, CO. Dick and I were both running 5 watts and we were 599 both ways. His antenna and high QTH makes up for a lot. At White Water State Park near St. Charles, MN I found a point on top of the bluff on the west side of the White Water River valley. Conditions weren't specticular but I did work KB3AAG, Frank, in Delphene, PA and N5GW, Gene in MS.

QRP / K1 Video

2007-06-26T21:56:00.002-05:00

Here's a video that I just posted on YouTube. In it I demonstate setting up my QRP station, show some of the features of my K1 and then talk a little about my QRP operating experiences. The video itself was done by John Reed K0KTY (SK) about 2 years ago.

http://www.youtube.com/watch?v=BUeJOuu5oUE

QRP Operating

2007-06-25T19:42:00.001-05:00

Today I finally made it away for some more QRP operating. This time it was to Great River Bluffs State Park (See http://www.dnr.state.mn.us/state_parks/great_river_bluffs/ ). This park is along the bluffs of southeastern Minnesota overlooking the Mississippi River Valley. From my operating position I could see far into Wisconsin and watch the hawks soaring below me. Using my K1 and a 32' endfed wire on 14.060 I worked both K7UP, John, in Elephant Butte, NM and W2BWQ, Gene, in Congers, NY. Conditions were only fair with QSB a problem. I heard only half a dozen stations across 20 mtrs.

On the 815 transmitter front it needs a better regulated suppy for both the 815 screen and the oscillator plate. The dropping resistors have to go.

A working 815 transmitter

2007-05-28T21:58:00.000-05:00

I have a working 815 transmitter. Unfortunately I had to "glue" a capacitor on to the side of the chassis to do it. Key to getting the final to work into a variety of loads is some sort of antenna tuner. Adding a capacitor into the grounded side of the output link does just that. The added capacitor does output loading . Tune up now amounts dipping the final with C2 and increasing/decreasing the loading with the added output link capacitor. Typical operation is 50 watts input and 35 watts out.

Eventually the loading capacitor will be hidden behind a front panel.

QRP (and a little homebrew)

2007-05-25T20:07:00.002-05:00

After a couple of days of on and off rain with cool weather here in SE Minnesota, today was sunny and temperature about 70 ... great evening for a picnic and a little QRPing from the park. We chose to go to Florence Park in Stewartville, MN. With my K1 and 67' endfed wire in a tree, 20 mtrs sounded pretty dead. An early CQ did raise K9PWK but QSB was bad and we lost each other before we really had much of a QSO (he gave me a 229). Finally at 6:45 Terry, N4IY, in Borden, IN came back to me. We had a nice QSO. His 4 watts was doing a fine 579 job.

On the homebrew 815 transmitter front I've been trying to get the final coil wound so that the transmitter delivers full output to a 50 ohm load. At this point I'm about to add an outboard antenna tuner to my project list.

2007-05-07T20:30:00.000-05:00

I've powered my new transmitter up on 40 meters.

For use during this test phase I built an adapter to allow the use of B&W 5 pin JVL transmitter coils instead of winding coils on my National coil forms. I'm also temporarily connecting the bias and voltage dropping resistor networks to the back 12 terminal barrier strip. This way I can easily play with the resistor values to get the right voltages.

The transmitter loads up to 40 watts input and 30 watts output with no sign of self oscillation

I've still problems, though. The 815 screen current won't come down. It appears to draw around 60 mA rather than 15. High screen current causes the screen dissipation to be exceeded, maybe damaging the 815. Right now I'm looking for another 815 to compare readings with.

A mid 30's Three Tube Regen

2007-05-06T12:42:00.000-05:00

I aquired another radio last week. This one I "won" through ebay. The pictures posted on ebay showed a fairly ughly set with three mis-matched dials. The layout, though, suggested the "Three Tube Regenerative Receiver of Unusual Performance" by George Grammer and written up in the January 1933 issue of QST.

I bid and the gamble paid off. Underneath the flaking paint front panel and cabinet was a fairly nicely done version of George Grammer's design.

George grammer's original article was more than another construction project. He spent a large part of the article talking about features of good regen receiver design before describing "a practical receiver". This receiver includes a tuned RF stage and general coverage/bandspread tuning. Bandspread tuning is via the drum dial at the left after the detector and RF stage bandset capacitors are set. The receiver showed up in the ARRL handbooks through 1937.

815 Transmitter Coil/L1

2007-04-25T21:40:00.000-05:00

L1 of my transmitter calls for ten turns on a 1" coil form spaced over 7/8". I had the form and the wire I needed. Winding spaced turns, though, takes a trick. I first wound the ten turn coil on the form, tightening the wire as much as possible. The turns were not even. It was not pretty. I then wound another "coil" (the red wire) forcing evenything to space out evenly over the 7/8". This I heavily coated with clear fingernail polish. After the fingernail polish had dryed I removed the red spacer coil and recoated with fingernail polish.

Picnic Table QRPing in Decorah, IA

2007-04-23T19:13:00.001-05:00

We spent the weekend in Decorah, IA and on Saturday and Sunday I had some spare time for hamming. I used my K1 with a 67' endfed wire up in the tree above the campsite. With the K1's built-in antenna tuner it loaded up on 40, 30 and 20. Sunday afternoon at 3:00 I did finally did have a QSO with Ken, WA8REI/4. He was on the Appalachian Trail at Newfound Gap, NC near Gatlinburg, TN. We were on 14.060, both running battery/5 watt power into end fed wire antennas. With some amount of QSB, signals were around 579. For the bottom of the sunspot cycle I was pretty happy.

See more examples of my QRP operating at http://www.io.com/~nielw/qrp/QRP_Stn.htm

Final 815 Transmitter Layout

2007-04-09T15:11:00.000-05:00

I've finally committed to a layout and mounted the major parts. From left to right along the front is the xtal (with B directly above it) C1 and C2. Left to right on top is 6V6, L2/L3, 815 and L4. RFC2 is mounted upright behind the 815 and L4. I elevated L2/L3 so that it could be mounted directly above C1. The toggle switch on top of the chassis in the right front corner is to short out L1 when not multipling in the tri-tet oscillator. The extra space along the back is reserved for whatever is needed to get the screen and oscillator voltages right. The spotting switch will probably go in the space between C1 and C2 with a cathode current meter mounted directly above it (if I add a front panel).

Final Layout / Drilling Guide

2007-04-07T16:19:00.000-05:00

After "playing checkers" for several days tweaking the layout, I'm ready to drill. I usually mark major component locations and holes using masking tape. After I'm done the tape can be removed leaving no markings on the chassis itself.

Another Power Supply Option

2007-04-05T07:48:00.000-05:00

Bryan, WA7PRC, pointed out to me that an "economy" power supply would be a more elegant way of getting the lower B+ needed for the oscillator stage then wasting power in multiple dropping resistors.

From Bryan:

"It's an easy way to obtain high- and low-B+ voltage sources.  In fact, there's more than one way to skin a cat... center tapped or non-center tapped transformer using a fullwave doubler.  In both cases, the output voltages differ by a factor of 2. The doubler, aside from needing a transformer with only a single secondary winding, has the advantage that the output voltage is 2.828 RMS instead of only 1.414 RMS.  So, your secondary can be 177VRMS instead of 354VRMS. Practically speaking, because of resistance losses, the voltage would be somewhat lower under load.  And of course, you'd still need whatever VA rating, so the transformer size/weight would be the same.

With either topology, you'll have a significantly lower low-B+, and should you decide to use a regulator, will not have to dissipate as much power in the series resistor."

815 Transmitter Power Supply

2007-04-04T19:55:00.000-05:00

I keep a couple of generic brute force power supplies around to use with my homebrew projects. This one grew out of a much modified and cannibalized WRL transmitter that I found at a swapmeet several years ago. From the back, on the right side is the high voltage section including transformer, choke, filter capacitor and rectifier tube. It will easily deliver the 500 VDC at about 200mA that I need for this project. On the left side is the bias supply. This section has a VR-90 with a pot across it. The exact bias voltage is set and then left alone. The six foot cable shown will plug into an octal socket on the back of the 815 transmitter.

QRP Operations from W0IBM shack

2007-04-03T17:56:00.001-05:00

Today was a great day to stay inside in SE MN: windy, overcast, temp in the 30s and snow in the forecast.

The first Tuesday of the month is informal meeting day at W0IBM, Rochester, MN. ( see http://www.w0ibm.org/ ) I took along my K1 as show and tell. 20 wasn't real active but I hooked up to the W0IBM three element yagi and managed a contact with George, KF4UCC, in Chesapeake, VA.

On the 815 transmitter front I've done a rough layout to help orient tube sockets and studied the dimensions a bit more. It still looks like it will fit. I'm just about ready put the drill to that virgin chassis.

815 Xmtr parts

2007-03-28T17:03:00.001-05:00

Here's the collection of parts needed to build my transmitter (the power supply is separate). I'll mount the male 8 pin plug on the back of the chassis for power. The barrier strip is for metering points and for the key connection. I'll be able to connect in a plate modulator here also. In the final transmitter the two 25 watt pots will be replaced by wire wound resistors.

Additional 815 xmtr Mod

2007-03-25T16:15:00.003-05:00

Another feature missing from most pre-WWII transmitters is some sort of spotting capability. Two reasons drive the need for spotting capability today. First, with transceivers being the norm, operators rarely tune the band looking for a response to a CQ. If answering a CQ, you need to be close to on frequency. Operating in an open spot on the band is the second reason for a spotting switch. Choosing the right operating frequency/crystal requires spotting capability.

To add a spotting switch to the 815 transmitter I'll try a DPDT switch connected in the cathode circuits of both the oscillator and the final. In the "spot" position it will key the oscillator just as the key and also open the cathode-to-ground connection on the 815. The crystal oscillator should operate normally letting me locate myself in the band but I'll not have 50 watts of RF overloading my receiver.

Another layout

2007-03-22T20:59:00.001-05:00

Here's another thought on layout ... move C2, the final plate tuning cap, from on top of to under the chassis. This frees up space top side and there is still enough space below for the parts around the 815. C2, a major shock hazard, is now safely under the chassis. I also found ceramic plate cap connectors for the 815. L4 is still exposed with voltage on it but it is set back from the edge fairly well and it is opposite the crystal socket.

815 Xmtr - Safety mods

2007-03-21T15:59:00.001-05:00

Someone asked me about modifying a vintage design in the name of safety. Sounds like a good idea to me. I already modify vintage receiver projects to keep B+ out of the headphones ( see http://www.io.com/~nielw/onestep/onestep.htm ). I also try to keep transmitter B+ away from accidental touching. This design, unfortunately, has 500 VDC exposed on the final tank coil and C2. I plan a couple of things to to help. First a front panel. I'll probably use a piece of masonite painted wrinkle black. As a bonus this gives me room for a plate current meter should I decide to add one. The second modification is to move the crystal socket to the front panel. No need to be reaching around behind the front panel to change frequency. The rest needs to be handled by being careful. Obviously power down when changing bands and short the tank coil to ground before touching it. Not so obvious is the key. Cathode keying allows one side of the key to float to B+. Usually one side of a key is more protected than the other. Connect this side to R1 and don't diddle with the key contacts with power applied.

815 Xmtr Parts Subbing

2007-03-20T21:20:00.001-05:00

As I search for parts, the topic of subbing parts has come up, particularly for C1 and C2. Miniture 140pf dual section variables are called out for both of these. In my junque box I fine slightly larger (physically) parts and, for C2, only a 100pf dual section variable. I can probably work around the 100pf problem by adding two fixed 50pf caps to L4, a 80JVL plug-in coil. The physical size increase appears to be OK for C2 but C1 is going to cramp the wiring around the oscillator stage. Can I shift C1 to tune L2 rather than L3? That reduces me to needing only a single section variable. Unfortunately is also means that I need to insolate "C1" from ground. The mounting starts to take up any space that I saved by changing to a single section cap. Looks like I'll stick with the parts I've found and just carefully lay out the oscillator stage in the space I have.

815 xmtr

2007-03-19T18:36:00.001-05:00

I'm to the point of starting to layout my 815 transmitter. Here are a couple of figures from the 1943 ARRL handbook describing this transmitter along with a picture of my preliminary layout. My chassis is 3"x 8"x12" so I have a little more room. Good thing, since I didn't have the small size variable caps called out in the original design. I'm also allowing room for a VR150 (seen on the back left corner) in case the oscillator stage needs regulated B+ for stability. The original design used only 3.5MHz crytals to cover 80, 40 and 20. I'm going to use 3.5 MHz crystals on 80, 7MHz crystals on 40 and 7MHz crystals on 20. This leads to one change. I'm adding a switch across L1/C3. This will be used to short out the cathode coil/cap when I'm running the tri-tet oscillator straight through.

815 transmitter

2007-03-18T13:05:00.001-05:00

According to the 1942 ARRL Handbook the 815 requires less then 2/10 of a watt of drive. A 6L6 is rated for much more than that. The 6V6 has the same base pinout but lower rating. I'll switch over to a 6V6 for the oscillator stage. My power supply will deliver about 500 VDC for the 815 but I don't want to run the 6V6 at 500 volts. I'll need to somehow drop 500V down to about 150 VDC for the oscillator stage. Depending on current requirements a VR150 and a dropping resistor might work. I don't want to use just a dropping resistor since then the 6V6 plate voltage could go as high as 500VDC with the key up.