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Saturday, February 29, 2020

A Dingey size Boat Anchor

I first started on this project over 15 years ago. I wanted a 6L6 based transmitter with a spotting function. Over the years it has gone through several iterations to the "Dingey Size Boat Anchor" I use today. Along the way I added a loading control, regulated the oscillator plate voltage to 108 volts, shifted the output circuit to a pi network and repackaged it in a metal cabinet to better match my HRO Sr. Like many projects it has been a journey. Here are a few more details about this transmitter as it stands today.

The circuit itself is fairly standard using a separate 300 B+ power supply. About the only thing I don't see in most designs is SW, the spotting switch. It allows me to check my crystal frequency against any station I might want to work or against QRM. As an important serendipity it also allows me to run the oscillator continuously while keying only the 6L6 output stage. This cuts down on chirp caused by the crystal restarting at the beginning of each code element. C10, the loading capacitor, is really two capacitors in parallel. One is a typical 300pf variable. The second is a 300pf high voltage "door knob" capacitor that can be switched it/out with a toggle switch.
Coils are what I could find. The 80 and 40 meter coils are commercial Bud coils that I had. I'm using only the tank portion, not the link. For 30 I found an old plug-in coil that looked about right and tried it. It works. In general look for coils that  dip and load to around 60% efficiency (ie. 6 to 7 watts output for 10 to 12 watts input).

Inside I arranged everything so that it made sense.  Across the back, left to right, is the 6J5 oscillator, the 6L6 final and then the plug-in output coil. Just to the right of the coil is the toggle switch that switches in/out the additional 300pf  loading capacity. The crystal socket is near the 6J5 and the 0C3 108 V voltage regulator is just to the right of that.

When changing crystals or, especially, coils it is important to recognize where high voltage is exposed. In this case the unprotected meter  terminals have 300 VDC, a lethal voltage, on them. Power this transmitter down when under the covers. This is even more important when working under the chassis. Don't take chances. Power down before working on it. As a safety modification consider placing the crystal socket on the front panel.

Are you looking for something more modern looking? Try  W1TS's 6C4-5763 MOPA in the October 1968 issue QST. Just add a resistor and 0B2 to regulate the oscillator B+ to 108V and include a switch to run the oscillator stage while keying the final.

Thursday, February 27, 2020

A Dingey size Boat Anchor on 30 mtrs

After putting my Drake 2B on 30 mtrs I immediately started looking for a matching transmitter.  The trouble is, the WARC bands like 30 mtrs weren't created until about 1980, long after the novice requirement for crystal control had gone away. By then solid state VFO controlled transceivers were becoming the typical rig. I'd need to homebrew a transmitter if I wanted vacuum tubes and crystal control on 30 mtrs.

A search of the QST archives brought up three articles that helped me decide what to do. The first was WD8DQT's article in January 2012 showing how to use today's HC49 crystals in simple MOPA (Master Oscillator - Power Amplifier) transmitters. The other two, W1TS's in October 1968 and WD8DAS's in January 2003 each show 6C4 to 5763 MOPA designs that can be modified per WD8DQT's article to use HC49 crystals.

What next?

I already have a crystal controlled MOPA transmitter on my desk. See . I did a quick check and found that the 6J5 I used is a close match to the 6C4 WD8DQT based his article on. I could start with the 6J5-6L6 transmitter I already had.  First I added a VR-105 and 12K 5 watt dropping resistor to power the 6J5 oscillator at 105 VDC. Next I converted the PA to a pi network instead of link coupled output. The tank capacitor is now 140pF and  the output/antenna capacitor is now 300pf plus, optionally, an additional 300pF. The coils on 80 and 40 are the same B&W output coils I've been using but without the output link connected. For 30 mtrs I searched through my junque box and found a coil that loads up fine on 30. Finally, I found HC-49 crystals, including 30 mtrs, five for $7.50 on ebay. See

My "new" 6J5-6L6 transmitter uses FT-243 and HC- 49 fundamental frequency crystals. It runs almost 12 watts input and about 6 watts out on 80, 40 and 30 ... outstanding! 

See ya on 30.

Sunday, February 23, 2020

Putting the Drake 2B on 30 and 17 meters

Recently I noticed the optional crystal frequency chart in my Drake 2B manual. It shows that a 14.0 MHz crystal allows you to listen to WWV on 10 MHz and 30 mtrs on 10.1-10.150. Nice, but wait, buy one get a second one free! The chart in the manual also shows that by retuning the preselector that same 14.0 MHz crystal also covers 17.5-18.1 MHz. This includes the lower half of the 17 mtr band. It looked like shifting the crystal up 100 KHz would shift coverage to include the entire 17 mtr band and still keep WWV and 30 mtrs on the dial. Outstanding!

A quick check of AF4K's website at shows that he stocks 14.1 MHz crystals in both the HC49 and HC6 style holders. Being cheap I bought the HC49 version for $12 instead of the HC6 plug and play option for $24. I mounted my new crystal on a hacked off HC6 base and plugged it in. It works fine.

Range C on my 2B now covers WWV, 30 mtrs and 17 mtrs.

Where is Solar Cycle 25?

Tuesday, November 26, 2019

Christmas Vertical

Each year around Thanksgiving through about New Years I give up my 40 mtr vertical. That vertical makes a great support for our Deck Christmas Tree Lights and the timing fits fine between the AWA Bruce Kelley '29 CW Party and the ARRL Straight Key Night.

Merry Christmas!

Thursday, November 21, 2019

AWA Bruce Kelley 1929 CW Party - 2019

Another BK is in the log. This year I worked ten other '29 stations. K0SM/W2ICE was worked outside of the party hours so Andy does not show up in my official BK log.

It was interesting that half of the '29 stations I worked were in MN and they all had, by far, the strongest signals. My 80 mtr antenna is only 15' off the ground. I suspect it was working well as a NVI antenna covering the "locals" fine. After trying all I could think of to clean up my 40 mtr signal I still wasn't satisfied so I stuck to 80.

My BK station stayed pretty much as planned for the first part of the BK using my new push-pull Colpitts and 1940 homebrew simple super but I felt I wasn't hearing as well as I might plus I was having trouble zero beating my own signal. I cobbled in my Drake 2B after the first night.  It helped but contacts were still pretty slow. I also noticed a lot of signal wobble because of wind. I see all of my MN compatriots are running MOPAs. They may have a point.

What's next? The ARRL Straight Key Night on New Years Day followed almost immediately by the AWA Linc Cundall Memorial CW Contest.

Friday, October 11, 2019

Winter Operating Events

The first of this winter's Classic/Boat Anchor Radio operating events is on the  horizon, only a few weeks away. I've been working on rigs since last spring. Now I'll have more chances to put them on the air.

First up is the AWA Bruce Kelley Memorial CW QSO Party in early November. This one requires that transmitters be of 1929 or earlier design and use tubes available in 1929. I'll use my Push Pull Colpitts with either an SW3 or my Simple Superhet. If things get really tough I'll move my KX3 over for the receiver.

Next is the ARRL Straight Key Night on New Years Day (UTC). This is ARRL's "Uncola" of contests (Does anyone remember those Uncola 7 Up ads?). It runs for 24 hours and has no scoring, only interesting QSOs. I'll probably bounce between several rigs but I think I'll have my Drake 2NT and R4B running as the primary station.

Right after SKN, in mid January, is the AWA  Linc Cundall Memorial CW Contest. In this one extra points are scored for rigs designed before 1950. I've three stations that would fit but I've just gotten my National FB7 checked out and running again. I'll operate it with my "CW Jr" as a 1934 station.

Next is the Novice Rig Roundup. The NRR emphasizes rigs from the early Novice era when novices had to be crystal controlled and run only 75 watts. My Heathkit HW16 is newer for me so I'll run it on 80 and 40 for this event. The backup receiver will be my KX3.

Finally, the AWA John Rollins Memorial DX Contest is in mid-March. This one emphasizes contacts on 40 and 20 using rigs designed before 1960. I'll have a chance here to use my Collins 75A4 with my Eico 720. This may not be a real DX station but, for me, it has a lot of class. 

Listen around and participate. All of these except the
Bruce Kelley Memorial CW QSO Party allow you to join in using modern gear . If you hear me give me a call. 

This winter should be a lot of fun.

Friday, September 20, 2019

FB7 / Parallel 46s Station On the Air

This week I finally finished up my early 30s CW station using a National FB7 and a homebrew 1934 transmitter. To-Dos that have been slowing me down are recapping the FB7, making a new power cable (and repairing the FB7 power cable) and then shoe horning everything into the corner I  have available for it. Does anyone else have a shack that reminds them of the old advertising slogan: "There's always room for Jello"?

I got on the air looking for signal reports and  RBN feedback. I had three QSOs that night (N4EDE/NC, W9BRD/NJ, W5RG/FL). All reported that my 10 watts sounded fine. W9BRD, even gave me a "first rate note" comment. 27 hits on the RBN said I was also getting out. Great! I've another fun station to put on the air and it is a perfect match for the January 2020 AWA Linc Cundall CW Contest.

What next? The AWA Bruce Kelley1929 QSO Party is coming up in November. I better get my  Push Pull Colpitts transmitter back on line, tested and ready to go.

Saturday, August 24, 2019

Drake 2-NT Transmitter

Last week I traded some of my 1930s heavy metal for a Drake 2-NT novice transmitter. At this point I'm interested in a decent rig I can carry rather than heavy weight shelf queens that need the next door teenager to get them out of the basement. What a great trade!

The 2-NT was introduced in 1966, late in the classic novice era when novices were still limited to 75 watts CW only and transmitters had to be crystal controlled. Around 2500 were produced. Within the novice restrictions the  2-NT had features that put it far above the competition. It was comparatively compact, included QSK or semi-breakin transmit/receiver switching and had receiver muting. Also, 80 through 10 meter coverage made it attractive beyond the novice license. The keying is set up so that the oscillator runs with a settable delay and the buffer stage is keyed to minimize chirp. Drake did a fine job with this rig.

The 2-NT was introduced with the Drake 2C but the 2-NT works well with a lot of radios that have a built-in mute function. The receiver mute function just needs to be designed so that the receiver mute terminal is grounded for receive and left floating for transmit.  This includes the Drake 2B, the 4 line (R4, R4B, R4C) receivers and the SPR-4 receiver. WARNING: Drake did this by wiring the mute function into the AVC circuit. Some radios may do this by controlling the receiver B+. I'd be careful running receiver B+ into my 2-NT.

Now I needed to decide which receiver to pair with the 2-NT. While a  2C would be nice and would cosmetically and market wise match the 2-NT, I don't have one. I do have a 2B, an R4B and an SPR-4. The 2B is a nice radio but it is of the previous generation. For now I'll leave it paired with my Eico 720. The SPR-4 is the same design vintage as the 2-NT and was Drake's first all transistor receiver. It is a fine example of what can be done with transistors in the mid 60s. Unfortunately Drake designed the SPR-4 as a high end SWL receiver. They didn't give me enough knobs to play with. AVC, bandwidth and passband are all fixed depending on the mode (USB/LSB/CW/AM) selected. Unfortunately the CW passband (and, therefore, the peaked CW pitch) is fixed at a higher pitch than my ears like. The SPR-4 went back on the shelf, possibly to wait for this winter and VLF experimenting.  The R4B has adjustable bandwidth and passband along with AVC choices and it is of the right vintage. Like Goldilocks I found my third choice, the R4B, to be just right.

Together the 2-NT and R4B work great. I'll certainly have them on the air a lot.

The 2-NT is also featured in the Sept 2019 issue of QST, Classic Radio column.

Monday, July 22, 2019

Push Pull 45s

In the November 1955 issue of QST I found this accolade to the Push-Pull TNT transmitter:

A Pair of 45s in Push-Pull
The words of
Keith S. Williams, W6DTY
The other day a few of us were sitting around chewing the fat, mostly cussing QRM, 'phone, c.w., single sideband, narrow-band f.m., Novices, old timers, the FCC, the ARRL, and the like. Joe Twerp, a ham of fairly recent vintage, remarked, "Seems like everybody you work nowadays has a Monster III transmitter. I'll bet it's used by more hams than any other single rig in the history of radio."

There was a general nodding of heads, all except for me and Hiram C. Hartley. Hiram turned to me and said, "Keith, do you recall the 'Complete Amateur Transmitter for Forty-Five Dollars'?"

"I sure do!"

History's Most Popular Ham Transmitter was first described in QST for November, 1930, in an article by George Grammer. Its immediate popularity was due to several causes, probably the most important being the Depression. It was pretty tough to keep beans on the table and a signal on the air at the same time. The standard transmitter of the day was a single 210 tube in a Hartley oscillator with 550 volts on the plate. This was a self-controlled transmitter, by the way, directly or inductively coupled to the antenna. Only rich guys had crystals and only a few were so far advanced technically that they could build a transmitter with two or more stages. Type 10 tubes cost money, and the power supply necessary in order to get decent output was almost out of the question for the majority of hams, whose billfolds were completely flat. A majority of broadcast receivers in 1930 used a pair of 45s in the audio output stage, with a Type 80 rectifier in a 350-volt power supply. Therefore. 45s and 80s were comparatively cheap and plentiful, and the corresponding power supply components were easy to acquire. The Type 45 had been a widely used audio tube for some time, but the manufacturers stated emphatically that the tube was not suitable for use as an oscillator so hams hadn't tried it in transmitters.

Grammer's article in QST stated that all parts for the push-pull 45 rig could be purchased new for $45.00 or less. Actually, the only parts ordinarily bought and paid for were the power transformer, filter choke and wet electrolytic filter condenser. All other parts, including the pair of 45s, were usually scrounged. (Many were the families who couldn't hear Morton Downey because Junior had pinched the 45s out of the family BC set and was upstairs stoking them up on 80.) In some cases the quarter-inch copper tubing for the tank coil had to be bought, but even this item could usually be managed without breaking the piggy. bank. The rig was built on breadboard. Well, it was actually built on anything handy, but rigs in QST were always built on real, honest-to-gosh. breadboards — the kitchen-cabinet variety. It was a push-pull self-controlled oscillator. It had a medium high-C plate tank for a modicum of frequency stability, an untamed grid coil, an antenna tuning condenser, and two or three small parts. It was simple to build and sure-fire in operation — the answer to a ham's prayer.

The appearance of this rig in QST coincided with a tremendous upsurge in the ham population. With the Depression, a large number of people found themselves with time on their hands. Those who couldn't get a steady job selling apples began to take up inexpensive hobbies in order to keep occupied while waiting for the NRA and the return of beer and light wines. Ham tickets began to be issued in droves. Commercially built ham gear, except for a few items like the National Thrill Box and the Pilot Super Wasp, was almost nonexistent and it was a rare would-be ham who could afford ready-made equipment, anyway. However, with Grammer's contraption you could get on the air for next to nothing and enjoy the thrill of talking to distant places by short-wave radio! Practically every new ham built the push-pull 45 transmitter and started out pounding brass on 80-meter c.w. Old timers who built a new rig in those days usually ended up with a pair of 45s in push-pull. Beginners generally started on 80 meters because self-excited transmitters usually tended to behave in a civilized manner on that band but could be unmanageable brutes on the higher frequencies. The push-pull 45 rig I had on the air in 1932 was very tame on 80 — most of the reports I received were either "PDC" or "NDC" and once in a while some liar would give me a "XTAL PDC" report and I would like to bust with pride. But on 40 meters, although the rig put out gobs of r.f., the note sounded like a buzz saw ripping through knots; on 20 meters the 45s ran red-hot and smoking while putting out about two watts to the antenna. I must say others had better luck.

Yes, indeed, that push-pull 45 rig was without doubt the most popular ham transmitter ever to be seen in W-land. After Hiram C. Hartley mentioned it the other day I got to pawing back among the stacks of old QSL cards stowed away on a closet shelf. I picked up a batch of old cards, circa 1932. Out of the first 38 cards, 24 cards said, "XMTR: PAIR 45s IN PP." That's 63 per cent, and I can easily believe that from 1931 to 1934 at least 63 per cent of all hams in this country were using that identical rig.

( Reprinted with the permission of the ARRL. Copyright ARRL.)

Wednesday, May 1, 2019

A fix for drift?

Does anyone else have a slow drift problem with their Hull Hartley? I was looking at mine and spotted something I wanted to check into.

The center tap resistors for the filament are mounted right under the tuning cap. Any heat they generate goes right to the tuning cap. Hull suggests 50-200 ohm resistors there. I used a couple of 40 ohm resistors thinking that as long as my power supply can handle the extra current draw I'd be ok. Now I have a .7 watt heat source where Hull's design had as low as a .14 watt heat source there. Any heat might cause a problem. oops.

These two resistors are in the circuit to provide a ground point for cathode keying, but there is an alternative. I have a center tapped 7.5 V filament supply. I can remove those two 40 ohm resistors and just key the filament transformer center tap. The heat source will be removed so my Hartley should now stay on frequency better.

*** clock ticks while solder smoke rises ****

Well, I removed the 40 ohm filament center tap resistors from my Hull Hartley. It is a fairly clean change. The only visible indication of the modification is the addition of one fahnestock clip along the left side for the transformer center tap connection. Now that heat source is gone.

I did before and after standby drift measurements. After tuning on the rig I checked the transmit frequency every 30 seconds for 15 minutes. Key down was only long enough every 30 seconds to get a transmit frequency readout. I had no load connected and the plate current was about 18mA with 300 volts B+.

Was is worth it?

*** Now drums rollllll ***

It depends

On 80 meters I found that the original Hull design drifted about 2KHz from a cold start while the modified version drifted about 500Hz. That's good but both took about 15 minutes to settle down. With both versions I still have to be careful about jumping on the air right after power on. I saw no significant change on 40.

But two parts were eliminated along with some amount of power on drift, both good things.

If I were starting out now building my Hull Hartley and I had a center tapped filament transformer I'd make this change. If I already had my Hull Hartley up and running, I'd probably let it be.