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Thursday, July 9, 2015

1T4 / 3V4 Regenerative Portable

Since getting a 3S4 QRP midget transmitter I've been thinking about building a receiver to match it. I wanted to use tubes along the same lines as the 3S4 and, at the same time, have a late 50s style. The late 50s/early 60s ARRL "How to Become a Radio Amateur" featured a two tube regen with a 3 1/2" National type K dial. That sort of style was what I was looking for.

I finally found the receiver circuit at Bob's Data: Useful Electronic Data and Project Plans and I have a National Type K Dial to set the style.

I've found the parts I need and have played with them to figure out a layout I like. The chassis is marked up and I'm ready to drill.

Tuesday, July 7, 2015

A Ross Hull Three Tube Regen

A couple of weeks ago I spotted a radio on ebay that looked really interesting. I've been doing some research on it since then.

This radio is a three tuber with a tuned RF stage, regenerative detector and a single stage of audio  ... not unusual for an early 30s shortwave set except for the mechanical layout. All of the tubes are mounted horizontally with the RF tube projecting through the RF/Detector stage shield.  This layout allows for a compact set. The National SW3, for example,  is a three tube regen with a tuned RF stage. It measures 9.5"x7"x9". This set is only 7"x5"x6.5", less than half the size of the SW3.

A search found the original described in the June 1931 issue of QST. Ross Hull designed this set to demonstrate the capabilities of the new type 33 audio pentode.  He bragged about the gain of the AF stage and being able to drive a speaker to good volume. Why, then, didn't he include a volume control? You have to detune the RF stage if a station is too loud. Along the way, though, Hull did, in typical Hull style, came up with the clever mechanical layout. Hull was also an early VHF advocate/experimenter. This layout allows fairly short leads. I have to wonder if he was thinking ahead to 60MHz when he sat at the drawing board designing this radio.

Sunday, May 3, 2015

Spring 2015 in the Park

It is warming up nicely here in SE Minnesota and the city parks are finally open. Yesterday I took my KX3 along with my 20 meter end fed zepp to Essex park here in Rochester. I didn't have a lot of action but both QSOs were neat. I finally had to QRT when the high school kids started showing up for prom photos and it looked like I might be in the background.

My first QSO was with NM5S in the Magdalena Mountains of New Mexico. He was operating SOTA (Summits on the Air). I've activited a couple of summits but no 10 pointers like Alan was yesterday. Later this summer I'll probably find a summit or two to activate myself.

My second QSO was with N1SZO. Rod was running 170mW using a
Rockmite transceiver and a 1/2 wave vertical. He was almost 100% copy here in MN, that's 5600 miles per watt!

I'm looking forward to more QRP outings to the park but next time I'll pack along a Coke and the BBQ grill so that I can make a day of it.

Saturday, December 20, 2014

2014 Bruce Kelley 1929 QSO Party

It was an interesting Bruce Kelley 1929 QSO Party this year. I learned a little more about using my own 1929 equipment and greater appreciation for the skill of those hams 85 years ago.

Getting my SW5 on the same frequency as my transmitter was the greatest challenge.
Fortunately I could tune my KX3 to my transmitter frequency using the KX3 as my code/signal monitor and then get the SW5 on frequency by tuning it and listening for the KX3 local oscillator.

I was never totally satisfied with the stability of my Hartley but, in reality, it may have been good enough of the BK. At the last minute I switched it out for my TNT. My TNT is a push-pull design with two tubes is push-pull across the tank circuit. Any inter-electrode capacitance change is cut in half so drift due to this capacitance change is also cut in half.

As mentioned earlier I tamed my SW5 considerably by converting the tuned RF stage to an untuned RF stage. This required only plugging a new "coil" consisting of an RF choke and capacitor.

All in all I made 16 contacts on 80 including Maine, British Columbia and North Carolina....not too bad for my 2-3 watts into a low endfed wire.

My friend W7BGO caught me on the air and recorded two of my QSOs, one with K0EOO and the other with KE0Z.

Listen to recording of my QSO with K0EOO and his 1926 Hartley:

Listen to recording of my QSO with KE0Z and his 1929 Hartley:

Thursday, November 6, 2014

2014 Bruce Kelley 1929 QSO Party

I'm making progress with this year's 1929 QSO party station. The SW5 works OK but I wonder if the grounding may have gone bad over the years. Nothing in the 1930's SW-5 literature hints at the sort of microphonics and feedback that I'm experiencing. I've tested the bypass caps by substitution and tightened all of the nuts/bolts I find with no change. Running it with an untuned RF stage seems to be the biggest help. Next is powering up my 1928 Hartley.

Pictured is my SW5 at the operating position and Hull Hartley on the window ledge. My Hartley tends to be microphonic because of the tank circuit construction. It can't sit on the operating table because just pounding on the key will be transferred to the transmitter causing the signal to wobble. The window ledge sits on the cinder block house foundation. it shouldn't be going anywhere. I'm using a National 5880-AB power supply (recapped, fused and cord replaced) with the SW5. The regulated power supply is for the Hartley...anything to make the signal as stable as possible. Also part of the station is my Elecraft KX3. The BK recommended operating windows are only 25 KCs wide, just a couple of dial divisions on both the SW5 and the Hartley. The KX3 will be my frequency meter and backup receiver.

Friday, October 24, 2014

2014 Bruce Kelley 1929 QSO Party

This year's AWA 1929 QSO Party is only about  1 1/2 months away.
The Feb 1931 QST cover inspired me to pull my SW-5 off the shelf to pair with my Hartley transmitter.

I found feedback within the SW-5 to be a problem. This isn't too bad for casual listening but it is a real problem for  on-the-air operating. Checking through my QST files I found the James Millen Sept 1931 article describing the design process for the SW-3. In it he talks about various shielding options. The SW-5 shielding looks a lot like Millen's first attempt at SW-3 shielding. He described the results as "most disappointing" and "the RF stage oscillated violently". My no holes solution? Turn the tuned SW-5 RF stage into an untuned RF stage. I inserted an RF choke and an antenna coupling capacitor into an empty SW-5 coil form and use it instead of a standard RF stage coil. Now the SW-5 RF stage stays out of oscillation and it still picks up plenty of 80 and 40 meter signals.

It looks like I may be able to use my new QSL cards after all.

Friday, September 12, 2014

Special Event Station K0M

A major focus for my spare time this past spring and early summer has been putting a special event station on the air. We ended up making 214 contacts over five days. See  for the details.

The equipment and focus wasn't particularly vintage or QRP (unless you count the 25 year old Heath SB-1400) but I did try out a new antenna (a MFJ-1777 102' center fed (with window line) doublet) and now I know more about setting up a special event station.

One advantage of a special event station is that there are no contest type rules. You can put as much into it as you wish. It could certainly be used to introduce other local hams to QRP operating or vintage equipment. A 1x1 call can even be reserved at . Fortunately WB4AEJ's posting at  covers a lot of the how-tos.

Wednesday, May 28, 2014

Function again wins

80 years ago crystals were expensive. Hams made do with one or two. Ads for the Utah Jr even touted two crystals will cover 160-20 meters. Swapping crystals to QSY up and down the band was not a high priority. The Utah Jr reflects this design philosophy. The one crystal socket is accessible only from the back and sits just in front of the plate loading cap with B+ exposed. Just the other side of the 6L6 is the plate loading coil with the same B+ exposure. Safe operating practice requires one to power down this transmitter before changing the crystal.

Today most hams have transceivers, they expect to hear a response to a CQ on their frequency. If I don't have a crystal plugged that puts me close to a station calling CQ he isn't going to hear my call. Powering down the transmitter to swap a crystal out takes time tempting me to cut corners.

The obvious solution is to extend the crystal socket so that I could change the crystal without digging in to the rig. I ended up building two versions. The cute one shown included 8" of TV twinlead and two crystals sockets wired in parallel. It sat on top of the Utah Jr making it easy to change crystals. The functional one had only  two wide spaced 3" leads running from a male 5 pin plug (that fit the Utah Jr crystal socket) to one crystal socket barely beyond the back of the transmitter. Running with the cute one resulted in a chirpy, harmonic laden signal while the other gave a clean signal. The cute one added about 7pf in parallel with the crystal while the functional one only added about 2pf. Maybe the extra 5pf causes a problem or maybe RF is feeding back via the 8" of twin lead. Either way, function wins over cute.

Thursday, May 8, 2014

Utah Jr Transmitter

The May 1936 issue of QST included an announcement of a new "Audio Power Tube", the 6L6, with a promise of more information in the June issue. By June the new 6L6 was featured as  "a high output crystal oscillator". In the second half of 1936 four transmitter designs in QST used the 6L6. The pace didn't slow down. In 1937 twelve QST transmitter designs used the 6L6. Clearly hams were excited about this new tube.

About this time Utah Radio Products Company in Chicago decided to begin offering kits that used their transformers. The Utah Jr was one of their first products. It was a single 6L6 crystal oscillator with self contained power supply. The Junior design appears to be based upon the "new Jones Regenerative Oscillator" described in the 1937 Frank C Jones Radio Handbook.

Ads featured the Junior as
an exceptional and outstanding value, especially recommended for the beginner and as the nucleus for a more powerful CW or phone transmitter. Experienced hams could even use this as an inexpensive standby or emergency transmitter. At $15.95 (less tubes, meter and crystal) this "professionally styled" 25 watt transmitter was heralded as the biggest bargain in the history of radio. With only two crystals it could cover 160-20 meters. It was the most amazing opportunity ever offered aspiring DXers. It could always added to without junking parts ( All Wave Radio, November 1937, pg 613).
With hype like this how could I pass one up when it was offered to me in a trade?

My Utah Jr was sold in the ARRL auction a few years ago. 
In general it was in pretty good shape with only a single obvious mod. Someone had done a nice job of adding a jeweled pilot lamp to the front panel. Pulling the RF deck revealed additional modifications to change the output to a pi network plus a variety of questionable caps, resistors and RF chokes, but no major problems. The power supply had already been recapped. It just needed a new bleeder resistor and three wire cord.

Restoration consisted mostly of backing out the RF Deck mods. The manual mentions wiring the loading capacitor in series with the antenna. This is needed for low impedance antennas. Given today's 50 ohm coax fed antenna systems this was the one change I made from stock. This then lead to dealing with the restricted loading range limited by the 250 mmf loading capacitor. I changed the coil socket to a five pin socket. This allows one pin to be grounded. Now I can add fixed additional loading capacitance as needed to the plug in coil to get close to 50 ohms. The stock 250 mmf loading cap is then used for the fine tuning/loading.
As an additional change I added easily removed binding posts to the back of the loading cap so that I can play with the fixed additional loading capacitors as needed.

Testing indicates that this little transmitter should do a great job for me. It easily runs 10-15 watts out on 80 and 40 meters and sounds good. For now I'll use it with my HRO Sr.
(My thanks to John Dilks, K2TQN, for his work to post a clean copy of the Utah Jr manual and schematic.)

Addendum, May 31, 2014:
Yesterday both K9LW and K8MRS reported a fine sounding signal. Another vintage transmitter is back on the air.

Thursday, April 24, 2014

Passing the Test

I understand the Maasi people of Tanzania and Kenya have a rite of passage for boys as they become men. Each must journey into the wilderness to kill a lion. Up until a few years ago we hams had a rite of passage. This one dictated by government regulation. Each of us had to journey to the nearest FCC office to be tested.

 Five stressful minutes and five intense seconds...

Six of us were seated around the worn table in the exam room of the FCC office in San Francisco. The window shades were drawn even though it was daytime. No fan could dispel the feeling of nervous tension that hung in the air. I'm sure each of us wanted to be there but we each also wanted the next few minutes to be over. I was no different from the others. I wanted to pass this test so that I could advance as a ham. Without a passing tic mark I'm off the air. To add to the pressure, sitting outside in the waiting room is Vance, my Elmer and new step-father. He had passed this same sort of test almost 30 years before. He was good at this and I wanted to demonstrate that I was good also.

Only the FCC examiner stood. I forget what he looked like. I was worried about the test, not him, but he had the power of a god. He would say if I continued with my hobby. He gave the instructions and reviewed the requirements. I was to demonstrate that I could copy Morse code sent at 13 wpm. He had a machine that had the code etched onto paper tape. Once started, his machine will send this code at exactly 13 wpm for five minutes. It would not stop, slow down or speed up. To pass I had to copy any one minute perfectly. One minute of code at 13 wpm, five characters per word. One minute, 65 characters, in a row, perfectly.
We six each put on our headphones. This was 1967. Ear buds weren't invented yet. These were "cans", two of them, each covering an ear, with a metal springy band across the tops of our heads to clamp them in place. Now I was focused. My world was those cans, my pencil and the government issued lined tablet in front of me.

The machine started. Focus, focus, di di di dahhh, "V", that's an "V", write it down. What was the next character? I missed it. Slow down, wait, you're going too fast. But the machine doesn't wait. One minute, 65 characters, in a row, perfectly , that's all I need, focus, focus. The dits and dahs keep coming. I'm hunched over my paper writing as fast as I can figure out what's being sent. I'm focused only on the sound in my ears. I see only the tablet in front of me. Suddenly "ker thunk". It must have been my sweat. Those headphones, slicked by my own nervous sweat, had slid off my head, falling to the table. Quick, put them back on. What have I lost? Maybe five seconds? Five or six characters? Start over. One minute, 65 characters, in a row, perfectly. But in those few seconds, with that ker thunk, I was finished. I could no longer focus.

I did fail that time but the world didn't end. I had copied enough code to earn my Technician class license. For a while I'd be WA6AVE using a Heathkit Twoer on AM. About six months later, sitting in the San Antonio FCC exam room (and more comfortable with my ability), I passed the code test. Today CW is my mode of choice.