A Trip Back to the 1930's.
1/6/2019 ~ A Popular 1930's Transmitter Circuit known as the Jones Oscillator used two tubes in Push Pull. Below is the creation of W9GT, Jack, which uses two 955 acorn tubes and produces in excess of 1 watt to the antenna. The rig is built into a wooden cigar box, which was a favorite building medium during the 1930's.
Dave, K4TWJ an avid QRP enthusiast and author who I now think is a SK published a schematic for a single tube 955 version as well as the Jones two tube 955 version which is shown below.
I have been advised to be wary of simply plugging the output into an antenna as there may be issues in complying with current FCC spectral purity standards. My bent would be to install a Band Pass Filter on the output side ahead of the antenna.
[For those who built the W1FB "Tuna Tin 2", you may recall that the ARRL revised the original schematic to add additional filtering so that there was compliance with the newer regulations.]
Major Caution Here! The Schematic for the single tube version as published in CQ is in error! If you print it out the Plus plate supply shows a DOT as if connected to what would be the GROUND side. The Correct schematic would have the Plate supply connected to the 2.5mH choke and that junction bypassed to ground through the 1NF to ground. What should be shown is that there is negative side keying to ground of the plate supply. This in itself is an issue as you have about 120 to 140 VDC across the key terminals. One solution is to find a high voltage PNP transistor and insert that into the circuit and key the plate circuit using a low voltage on the base.
Another approach is to open the Cathode connection to ground and key the Cathode -- you might need a small value resistor for a bit of wave shaping. The two tube version uses Cathode Keying!
Acorn tubes were essentially UHF devices that had low filament current requirements and were plentiful as war surplus components. The plate voltage was a modest 130 VDC. I once bought some at a price 2/$1. Now if you can find them more like $10 each.
More 1930's Transmitters...
Recently my good friend Bill, N2CQR had on the air a two FET transistor transceiver operating on 40M CW using a single crystal. The further challenge aside from a single rock, was using but 100 milliwatts of RF power to a wire antenna. This marvel which he dubbed the ET2 had one J310 FET operating as a regen receiver and the second J310 was a crystal oscillator stage.
Netting some two dozen contacts in multiple states over a 6 week period of casual operation, such a feat today must be viewed with awe, astonishment and down right envy! The ET2 having been mounted on a wooden plank is now affixed to the wall of his shack not only as a testament of accomplishment; but as a piece of living art.
We should also highlight that such simple rig while very uncommon today was very much the main equipment in ham stations during the 1930's -- although quite possibly the transmitter of those days put out at least 5 watts (about 5 orders of magnitude more fire in the wire).
N2CQR quite openly admits that operating the ET2 was a challenge -- not because of the 100 milliwatts; but because of a single frequency. He categorically stated that in the "old days" operators had a separate receiver and transmitter and often worked stations not on your same frequency. Today most hams operate using transceivers and if you are not in their receiver pass band --you are simply ignored. That indeed is today's challenge.
Bill's adventure's caused me to reflect on the comparison of a ham shack 90 years ago to one of today. But more importantly an evaluation of the cost/enjoyment/excitement value.
Things just seem to show up on my phone most of it ham related and I marvel at what I recently saw. Here is what showed up this week: a shack that had a FLEX 6700, an Apache Anon and a Elecraft K4. Behind each rig was a very large (37 inch) 4K monitor and of course the usual array of linear amplifiers, one for each rig. Undoubtedly outback was a huge antenna farm. Quite possibly the investment exceeded $100K. There was also a low budget one I saw that had just a FLEX 6400 and a 19 inch Monitor (perhaps only $4K).
My friend Bill maybe had $20 total invested which is more in line with the ham station costs of the early 1930's. The latter part of the 1930's as things got better economically here in the US, we started to see some pretty nifty receivers that were a huge step up from the simple regenerative rigs. But in large hams still built their transmitters where now the power levels once more took a leap to the 50 to 100 watt range.
Certainly the 1930's rigs were better than the original spark gap transmitters of the 1905-1915 period. The year 1912 was pivotal as that is when regulations (200 meters and down) and the establishment of ham licensing took place. Keep in mind that it was in 1888 that Heinrich Hertz discovered radio waves. So a mere 40 to 50 years later, world wide communications took place with simple one tube receivers and one tube transmitters. Now hams spend $100K to do that and we still have no sunspots --but we have the expensive equipment when Cycle 25 finally peaks about 6 to 8 years from now.
The IARU stated that hams are hams for two reasons: Contests and Operating! I don't agree with that position as I think there is also a group that likes to tinker. True you can only tinker if you have some skills (The Knack) or as I like to say "you have to know stuff to do stuff". N2CQR took up the ET2 challenge as it was not a simple build this circuit. But Bill actually had to develop some circuitry to make the ET2 (tinker phase) and then got to the operating part.
I closely followed Bill's adventure during that 6 week sojourn and you could tell he was not only excited that this was a viable working transceiver; but that he was in a sense "reliving" the 1930's. Here he was making contacts with a rig built with his own hands and costing about as much as a trip to McDonalds for a quick lunch! Bill added a bit of flair to his creation -- for every contact he "logged" the QSO on the wooden breadboard with a sharpie pen. It doesn't get any better than that!
But the point I earlier made about cost/excitement/enjoyment aspect. You would hope that after spending $100K that you are having fun -- Friend Bill certainly can claim low cost, plenty of enjoyment and very exciting to make contacts with a rig developed and built with his own hands. I suspect that Bill's buttons are popping with pride that he can get on the air and have QSO's and there is not $100K worth of gear just waiting for a sunspot!
So even though as of 2007, US hams no longer need to demonstrate a proficiency in CW as a condition for getting a license nonetheless there is still an interest in CW as a means of communication. I frequently hear as I work SSB with my homebrew rigs, the op at the other end says "I spend time on CW as well as SSB".
The 1930's has been called the "Golden Era" in commercial radio broadcasting and that is also extended to amateur radio operations. I do not wish to overlook today's technology and the fact we have radios that can look at 15 MHz of spectrum on a 72 Inch HD screen to see what bands are open. But that technology for most hams must be purchased as the skills and tools required to homebrew such rigs are beyond the general ham population. But there are hams who continue to do this pioneering work -- thankfully.
What would you do if you could actually build a 1930's style ham rig? Would it be as much fun as operating the FTdx101D or maybe the FLEX 6600 or the K4. You might have to build one to find out.
Below is a typical early 1930's station! Two #30 Tubes in a Regen Receiver and a #10 in a Harley self excited oscillator. One problem with the self-excited Oscillator -- the antenna! If the antenna shifted in the breeze --its loading changed and that was reflected back into the tank circuit -- the signal moved about in frequency as the wind changed. That was 1930's excitement! Notably missing: no 72 inch 4K OLED screens!
As I looked for some examples of the 1930's transmitters and receivers it was evident that "ugly construction" awaited to be invented. It appears the favorite form of construction was a wooden base plate perhaps totally "al fresco" or perhaps even sporting a metal or wooden front panel. Clearly there was a sense of pride in their creations!
Below is a typical early 1930's station! Two #30 Tubes in a Regen Receiver and a #10 in a Harley self excited oscillator. One problem with the self-excited Oscillator -- the antenna! If the antenna shifted in the breeze --its loading changed and that was reflected back into the tank circuit -- the signal moved about in frequency as the wind changed. That was 1930's excitement! Notably missing: no 72 inch 4K OLED screens!
As I looked for some examples of the 1930's transmitters and receivers it was evident that "ugly construction" awaited to be invented. It appears the favorite form of construction was a wooden base plate perhaps totally "al fresco" or perhaps even sporting a metal or wooden front panel. Clearly there was a sense of pride in their creations!
Stay Tuned. Those who know stuff, can do stuff!
73's
Pete N6QW
Pete N6QW