1930's Portable Transmitter - Part 3
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- เผยแพร่เมื่อ 21 ต.ค. 2024
- Let's get the Old Time Transmitter wired up and on the air for some 40 Meter QSO's. What we are making is POTA 1930's-Style Portable setup that will be used a an authentic CCC Camp Museum.
This is very interesting! I love old technology!
Old stuff is cool again.
I remember seeing those big old B batteries for sale at the local hardware store back around 1960. I didn't know what they were for. This is so educational and fun to watch. Great concept, Mike.
They were for portable radios using battery tubes and also for the Bell System remote telephone equipment. I also saw them at Ranger stations in Fire Towers.
Fascinating
Very cool Mike. Keep building so we can keep watching and learning. 73's🎙KD9OAM
That is neat, you can get 2.1 watts in push-pull class B amplifier out of two 30 tubes. The RC-12 1934 RCA tube manual specs on this tube, confirms this power output. Otherwise the 30 was just considered a detector/amplifier tube before that year and you would not think it was used as a transmitting tube!
I made a Hartley with an ordinary 201A and it also did pretty well, which surprised me.
In your Part 2 1930's Portable Transmitter video you expressed your concerns about the choice of transmitter circuit. I'll give you credit for persevering on. You got it working - 4 watts out ! I checked my 1938 Handbook and see Triode push - pull circuits with the RFC center tapped the Tank Coil with Split - Stator condencer across the Tank Coil. It looks like both Triode Cathodes are grounded to the rotor of the Split - Condencer. Keep up the Great Work. I'm Learning a lot from you.
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This works fine if you feed the plate coil with an RFC. But if you then ground the RFC with an AC bypass; then it stops oscillating.
good job sir !
Thanks for watching my channel.
Beautiful to see old equipment being brought back to life
It was not old he just built it.
@@Capecodham that's a really good replica in that case
Looking great Mike - love your proposed battery solution...
Great work, Mike! Please show us the inside and underside of the TX now that it’s wired. Congratulations on the nice QSO’s!
I will do that next time. The coils are commercial of course, but they could easily be done on a couple of chunks of PVC or with standard plug in coils.
Elegant, Nice job of moving from schematic to a working prototype, looking forward to your DC to DC converter.
Its coming this week. Then to integrate it into the box.
I enjoy all of your home-brew projects but particularly this one since you are focusing of the early tube circuits. Can’t wait until you take the RX and TX to the field.
Sam AE4GX
Next will be integrating the HV into the box and testing.
I have an old (1960's) Triad toroidal inverter transformer rated at 6v in, 300v out that I could use to build a transistorized inverter. Back in the day, it would be built with "door knob" GE power transistors (DS501) from car radios, but today, I'd probably us IRF N channel Mosfets.
Yes and I'm sure you remember the Heathkit Mobile supply. Just bog multivibrator oscillators.
I built 2 converters. One is hooked up to a two tube Acorn transmitter. 12v converted to 200 and some volts. Rex Harper QRPme , well his tube transmitter acorn kit uses the inverter.
Very Nice. If I was to do this again I would have done a MOPA rather than a push pull.
Hi Mike. Can't send link, but I did a rough video on how I think the Jones tx works. It 's just from an Ac perspectuve, ignoring bias. Its the only video on this channel so you can go in and have a look. Or not 😃.
Please send it along!
Great project! Thanks and 73 (or is it 72?)
Mike: I think Frank Jones would be very pleased, even with your innovative use of the drone battery and the inverter plug. What great fun! I was listening to you on the Old Military Radio Net this week (I am back in Virginia) and listening on my homebrew Mate For the Might Midget Receiver. You were armchair copy on your first transmission but QSB got you by the second. Hey, when and on what freq is the Vintage Sideband Net you mentioned? 73 Bill N2CQR
3804 kHz LSB, Mondays 830 EST, WA2RAS Jeff NCS
16:00-
That note when keying sounds sweet
Well nobody complained about is "flavor" . The big issue never changes. Crystal control is very limiting.
I'm reading my 1942 Handbook article about single 6L6 crystal control transmitter. The accompanying Antenna Tuner uses a combination of panel lamps ( No. 46) and a 1/4 watt neon bulb to indicate resonance in antenna circuit and relative power output. The article goes on to explain that the lamps will indicate if "the length from the far end of the antenna to the feeder terminals is near an odd multiple one-quarter wavelength for the frequency of operation, while the neon bulb will be useful where the length is near an even multiple." Is this another way to describe " low Z and high Z" ?
Very cool and essentially the problem with random wires with no tuner. If I use a half wave, it will be a voltage point at the transmitter and very little current to light an incandescent bulb. But a Neon Bulb would indicate. With a Windom single wire offset feed, I would have to explore the taps on the coil to get the best match. Those are the two period correct (POTA) antennas I'm considering for the field work.
You might want to open that inverter up and see about taking DC from it directly, first stage in such a thing is a boost converter to some fairly high voltage (IIRC around mains peak so like 170-180), followed by a low speed switching stage to form the "modified sine wave" that's a somewhat nasty thing to rectify. If you're lucky the control chip will have English or translatable Chinese documentation available, making voltage adjustment easy.
Wow. That is for another video! Great tip.
For your Ant Output..
Could you add two more binding posts...
Lo.... Med... Hi Z outputs without opening the case... Using (almost) anything as your antenna???
Excellent thinking. Next time you see it, I will have maybe two more taps!
prearranged contacts next door? How about a 1830 station? Go to your ESSO station and get some gas and put it in the tank in this transmitter, it will double the power.
Are you volunteering for my field day experiment?
Could you lose CG1 and CG2 and have a feedback coil connected to the two grid connections and a 1M0 Resistor to ground and I suspect you can keep the crystal in and it should work as an oscillator, the feedback coil would get it's drive from the output, that oscillator is essentially a Royer Oscillator.
Yes this would be a traditional inductive feedback push pull oscillator - Meissner Style sometimes called a Meissner 4-Coil. This was a popular oscillator transmitter in the early 1920's competing with the push pull Hartley and other types.
I can see you going to walmart for them 9V batteries and they do not have enough in the store and you have to drive to 2 or 3 walmarts to get enough batteries . If using 12V they have a common DC to DC converter to make 5V from 12V that covers filament .Just some ferrite in converters to cut RFI if needed. 3 NiCD cells would do filament as well.I don't think 2 would have enough voltage . Use what you have on hand . so many ways to do that battery supply. 73
I ordered a stack of them off Amazon and they were counterfeit. Only half were even hooked up internally!
You can clean up voltage these days . But if you want high voltage use a couple of 48 volt batterys or 4 in your case most b batteries were 90 volts. 73
The Dogsled Transmitters used on the 1928 Byrd Antarctic Expedition used 360V with a 180V Center tap for the oscillator. This allowed two tubes, one as a crystal oscillator and one as a Class C final to produce over 4W. Special insulated battery boxes were made to hold the batteries externally for the cold temps.
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SG3525 easy inverter schematic could be a good solution.
@@maxzile4860 use a voltage doubler or more. I remember them big finned rectifiers used in old black and white TVs. Just use a power transformer and a 5u4 tube. And capacitors to filter. 73
th-cam.com/video/T8C7dp0U3Ig/w-d-xo.html A very interesting chip indeed, and operating around 50 kHz.
If you RF ground both PP, L and C, don't you just get two tanks that just happen to be close together? Also, I thought you were going to make some sort of hand crank HV generator, where you have to crank and send at the same time? I guess you could crank with your hands and send with your left foot, hence QLF skill? Well, I have a ARC5 TX dynamotor somewhere, if you get fed up. I have recently messed with a few of those fleabay HV modules. They really are lousy, and dirty: poor designs. I am massaging one now, to run a VHF pencil tube XCVR..... but got distracted with refabb'ing a free NC109. ADHD + retirement = fun! 73 de W3IHM
I have had sets with noisy dynamotors (audible I mean) but never one that is so bad with hash or unshielded, that it upsets the reception in a good design.