Nice work.
I had tryed many times. Basicly it starts no matter the gang position, it doesn't make any difference if I turn it. Only if I have DMM connected (ground and plate), then it needs to be fully counter clockwise and it has few degrees of headroom before it stops working and voltage drops to -0.70.
Yep, it works that way when DMM is connected.
Nice. It's winter here, we had snow few days ago. Grrr
I get -1.25v on the grid and I have silent tone on the receiver about 3000hz by ear.
Buzz disapears when I turn off the oscillator, while tube is cooling down only 3000hz tone remains audible.
Well. Try to reduce the 220pf at the right of the Xtal (as I drawed in the circuit) some value arround 47/56/68 pF.
I have no clear the reason for the ~3000Hz note, it may be an heterodyne with other signal.
Also try disconnecting one side of the gang or both and confirm that it isn't shorcircuited internally. Sometimes the thin plastic film that acts a dielectric may be broken.
Also check tube heater voltage. I don't understand why the oscillator can't give almost 5V of bias in the triode's grid. If the tube is used, perhaps it is exausted or faulty.
I have no clear the reason for the ~3000Hz note, it may be an heterodyne with other signal.
Also try disconnecting one side of the gang or both and confirm that it isn't shorcircuited internally. Sometimes the thin plastic film that acts a dielectric may be broken.
Also check tube heater voltage. I don't understand why the oscillator can't give almost 5V of bias in the triode's grid. If the tube is used, perhaps it is exausted or faulty.
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Indeed, Armstrong is the inventor of this method. In the early 70s, curious why this method had been abandoned, I started constructing a semiconductor version (fundamental frequency 200 KHz) and found out the real problem: it's the amount of frequency multipliers. Unless each stage is thoroughly isolated from the others, there's enough feed-through to mess up the spectrum. The proper way would be to use a few PLLs and binary dividers, back then expensive.
Many international broadcasters are using hired transmitters as close as possible to the target area. So here in Panama I can here a program in English from the Czech republic on 15,770 KHz - a transmitter located in Florida, USA: http://www.wrmi.net
One of the few "from home" broadcasters is RRI (Radio Romania International). Very powerful transmitters (100 KW), good directional antennas and also quite a few transmissions in DRM (recently updated from 2.5 to 5 KHz audio).
you got yourself a treasure trove, lots can be done with those tubes, congratulations....
The 3000hz tone was indeed from some other signal. It's not here today.
Heater voltage is 11.4vac, that would be about 8v rms... that is a bit low...
I can try with DC from adjustable psu.
Will test the gang and find what cap I have to replace 220pf.
Tested the gang on 200mOhm range... it's just L (for out of range) showing on the DMM.... tryed to replace gang with the other one... same results...
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Changed heater psu to dc 9v...
triode's grid voltage is -0.54v (but it seems to be higher if DMM is not connected, because I can see the voltage falling quickly when I connect the DMM, it shows -0.65v at first fraction of a second.
Plate is 78v with gang far CCW and 55v with gang far CW.
It does a nice consistent fall while turning the gang and buzz starts to go attenuated when voltage gets pass 67v and lower. But just when I have DMM probe on the triode's plate or pentode's grid, otherwise gang position still makes no difference.
Pentode's grid voltage is -0.91v with gang far CCW and -0.61v with gang far CW....
Pentode's screen voltage is -5v...
Edit: changed the 220pf cap for 100pf (as I dont have 47, 56 or 68pf) and triodes grid went to -2v... will check my scrap pcbs for the lower cap... this looks promising.
triode's grid voltage is -0.54v (but it seems to be higher if DMM is not connected, because I can see the voltage falling quickly when I connect the DMM, it shows -0.65v at first fraction of a second.
Plate is 78v with gang far CCW and 55v with gang far CW.
It does a nice consistent fall while turning the gang and buzz starts to go attenuated when voltage gets pass 67v and lower. But just when I have DMM probe on the triode's plate or pentode's grid, otherwise gang position still makes no difference.
Pentode's grid voltage is -0.91v with gang far CCW and -0.61v with gang far CW....
Pentode's screen voltage is -5v...
Edit: changed the 220pf cap for 100pf (as I dont have 47, 56 or 68pf) and triodes grid went to -2v... will check my scrap pcbs for the lower cap... this looks promising.
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Yezzzz. Short waves had been used during decades for international transmissions. I remember had ear that there were stations with 500KW! Think your oscillator is about 1/2W, so it equals 1 million oscillators like your one. Sincerelly I don't know if actually the SW stations are on air. I remember Radio Netherland, the VOA (Voice of America from USA), RFI (Radio France Internationale), RTE from Spain our RAE (Radiodifusión Argentina al Exterior), TELAM (our official news agency), etc. Several stations those era had spanish language transmissions and they gift some kinds of things: Radio Netherland send once a year the entire program for spanish transmissions to South America. Thus I listen several sundays a program called "La estación de la alegría" (the funny station). We wrote them and I remember a white, red and blue cubic box that function as a calendar, money box and had the station logo in one face; and a QSL card they sent at mail return (no email nor internet yet).
This includes the now extinct RTTY, only actually use by some few hams around the world.
I am not sure if it was during the Gulf War, I received in a short wave tube General Electric radio some RTTY signals. They were SSB (Single Side Band, the normal AM transmission but the carrier and one sideband [AM has two sidebands at each side of the carrier] removed by a special cristal filter). So you need a beat oscillator to listen them properly. RTTY sound is fun. Thus, with my brother Rolo now in USA, we built a simple converter with a TL081 powered from the serial port of a 386 PC. The opamp ran open loop and only convert sine waves into square waves and those was input into the serial port DB25. An old program HAMCOMM runing under DOS 5.0 let we see in the screen the teletype texts. One must descifre it because signals were weak, l lack a proper aerial and the beat oscillator (6BZ6) was far from perfect at those times knowedge. So the original text was mixed with abnormal characters like:
"Sinc4 thosw timz to nowwm6ch @Ears $ad p%st"
The obvious text was:
Since those time to now much years had past.
But characters appear quikcly at the screen (75 characters per minute) and there was no time to reread, so one must be fast to understand the text.
In fact we read by those means news that never was said in the radio ot TV during those times.
Those era of analog communications...
This includes the now extinct RTTY, only actually use by some few hams around the world.
I am not sure if it was during the Gulf War, I received in a short wave tube General Electric radio some RTTY signals. They were SSB (Single Side Band, the normal AM transmission but the carrier and one sideband [AM has two sidebands at each side of the carrier] removed by a special cristal filter). So you need a beat oscillator to listen them properly. RTTY sound is fun. Thus, with my brother Rolo now in USA, we built a simple converter with a TL081 powered from the serial port of a 386 PC. The opamp ran open loop and only convert sine waves into square waves and those was input into the serial port DB25. An old program HAMCOMM runing under DOS 5.0 let we see in the screen the teletype texts. One must descifre it because signals were weak, l lack a proper aerial and the beat oscillator (6BZ6) was far from perfect at those times knowedge. So the original text was mixed with abnormal characters like:
"Sinc4 thosw timz to nowwm6ch @Ears $ad p%st"
The obvious text was:
Since those time to now much years had past.
But characters appear quikcly at the screen (75 characters per minute) and there was no time to reread, so one must be fast to understand the text.
In fact we read by those means news that never was said in the radio ot TV during those times.
Those era of analog communications...
Now thats some history.
I found 47pF cap and I think that it is good now 🙂
-4.2 on triode's grid
102v on triode's plate
-1.65v on on pentode's grid
-5.30v on pentode's screen
-2V sounds better. The target would be to get say -8V at least.
If you have a idle time, please refresh me which tubes do you have to play with. Is there any xCL84? (Where x means E or P according tube heater ratings).
If you have a idle time, please refresh me which tubes do you have to play with. Is there any xCL84? (Where x means E or P according tube heater ratings).
Ok, if I have -4.2 now with 47pF, can I try 27pF?
PCL86
PL504
PCF801
PCF802
ECH84
PCC88
Okay. Always search the best point with the gang. And perpaps you can use the signal cap too to get more capacitance in the tuned circuit. For this, short both ends of the little gang.