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Sunday, December 13, 2009

1928 Hartley / AWA 1929 B Kelley QSO Party

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 Vertical 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.

Monday, November 16, 2009

1928 Transmitter Tuning

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.

Sunday, November 15, 2009

1928 Transmitter Signal Quality

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 Kelley 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".

Friday, November 13, 2009

1928 Hartley Coils


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.

Friday, November 6, 2009

More 1928 Hartley

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:


Friday, October 30, 2009

More 1928 Hartley

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.

Wednesday, October 21, 2009

More 1928 Hartley


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.

Monday, October 19, 2009

More 1928 Hartley




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

Thursday, October 15, 2009

More 1928 Hartley


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.

Wednesday, October 14, 2009

More 1928 Hartley


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+.

Tuesday, October 13, 2009

More 1928 Hartley


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.

Friday, October 2, 2009

More 1928 Hartley


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.

Tuesday, September 29, 2009

A 1928 Hartley

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 thr
ough 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.

Sunday, September 27, 2009

Camping and Picnic Table QRP

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).

Tuesday, September 22, 2009

More 1934 Transmitter

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.

Wednesday, September 16, 2009

A 1934 transmitter - On the Air

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.

Sunday, September 13, 2009

More 1934 transmitter - It Works!

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, two phone jacks are for metering plate current and the third is for the key. If in the heat of the moment I get the three 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 of what I've done 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.

Friday, August 28, 2009

QRP Operating at Crater Lake National Park


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.

Thursday, July 9, 2009

More 1934 Transmitter


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.

Monday, July 6, 2009

QRP from Frontenac State Park

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....

Sunday, May 31, 2009

More 1934 Transmitter

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.

Friday, April 10, 2009

More 1934 Transmitter


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.

Thursday, April 9, 2009

A 1934 Style Transmitter

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.

Saturday, February 7, 2009

QRP FYBO Contest


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.

Wednesday, January 28, 2009

AWA Linc Cundall OT CW Contest (Part 2)


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.

Friday, January 23, 2009

AWA Linc Cundall OT CW Contest



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.

Wednesday, January 14, 2009

An Iambic keyer rated for cathode keying



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://wb9kzy.com/keyallhv.htm ) to make a keyer capable of keying up to 500V. 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.