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Uwe wrote in message ...
With the help of some folks here I did troubleshoot my AC-1 tube transmitter (using a 6V6) and got it working somehow. Since I passed my code test and had my first QSO using the transmitter and boy was that exciting. But questions remain. I monitor the output signal on my scope and notice that right after key down the waveform contract just a bit and the tone changes pitch. I guess this is called chirp. I normally use B+ 200V. If I increase the voltage lets say to 300V this effect becomes much more pronounced. I still use an external bench supply capable of much higher currents and I don't think it is a power supply weakness. In fact putting a VOM on the supply line shows no sag in my supply voltage. How can I minimize this and especially keep it from becoming more severe at higher outputs. Also, the circuit diagram for the tranmitter did not state the coil diameter of the pi network. The pi network still has me scratching my head. Coils with slight variations in diameter give dramatically different results. Also changing the air cap with one of an identical range can have a vast effect, which surprised me. Is this the "real world components" versus the theory??? Uwe ---------------- Congratulations! I still have my original Ameco AC-1 15-Watt CW transmitter, completely intact with all original parts and accessories, all in perfect like-new condition, and a copy of the whole manual. If you want me to look at or measure anything for you (e.g. the coil you mentioned?), just let me know. I am at tomg AT fullnet.com . By the way, I think that I paid $14.98 for the Ameco AC-1 kit, new, back in about 1969. I built it, tested it, and then never used it. And I HAVE had people offer me hundreds of dollars for it, "out of the blue", several times over the last few years. There's a picture of it on my webpage (see URL, below). Good luck! Regards, Tom Gootee http://www.fullnet.com/u/tomg ----------------------------- |
Only now do I have a chance to react to some of the suggestions... I guess one poster here is right, I will just have to fiddle a bit more with the pi network (since at the B+ voltages suggested here my plate current would be way high) and I will have to live with the chirp. Nobody has complained yet anyways and maybe the chirp is worse in my receiver than on the air, as someone here suggested. By the way I use a Icom R75 for a receiver and switch the antenna off during transmit-still plenty of a signal seems to get into the receiver anyways. By the way, I see suggestions how to just "stretch" crystal controlled oscillators a bit by adding a suitable coil and capacitor in series with the crystal. Has anybody tried that with the AC-1?? Would be nice to be able to get out of the ways of some of the big power guys. Any suggestion would be welcome. Uwe |
Only now do I have a chance to react to some of the suggestions... I guess one poster here is right, I will just have to fiddle a bit more with the pi network (since at the B+ voltages suggested here my plate current would be way high) and I will have to live with the chirp. Nobody has complained yet anyways and maybe the chirp is worse in my receiver than on the air, as someone here suggested. By the way I use a Icom R75 for a receiver and switch the antenna off during transmit-still plenty of a signal seems to get into the receiver anyways. By the way, I see suggestions how to just "stretch" crystal controlled oscillators a bit by adding a suitable coil and capacitor in series with the crystal. Has anybody tried that with the AC-1?? Would be nice to be able to get out of the ways of some of the big power guys. Any suggestion would be welcome. Uwe |
"Uwe" wrote in message ... By the way, I see suggestions how to just "stretch" crystal controlled oscillators a bit by adding a suitable coil and capacitor in series with the crystal. Has anybody tried that with the AC-1?? Would be nice to be able to get out of the ways of some of the big power guys. Any suggestion would be welcome. An rf choke or variable inductor of between 7 and 20 uH in series with a variable cap of about 200 pF in series with a crystal, will pull the frequency. It's called a variable crystal oscillator or VXO. You're probably using FT-243 crystals, though, and they don't pull very far. I have to say this again: Time to put this thing on the shelf. For the time and trouble you are putting into it you could build a solid-state rig that would put out as much power, have a VFO and not contain life-threatening voltages. 73, "PM" |
"Uwe" wrote in message ... By the way, I see suggestions how to just "stretch" crystal controlled oscillators a bit by adding a suitable coil and capacitor in series with the crystal. Has anybody tried that with the AC-1?? Would be nice to be able to get out of the ways of some of the big power guys. Any suggestion would be welcome. An rf choke or variable inductor of between 7 and 20 uH in series with a variable cap of about 200 pF in series with a crystal, will pull the frequency. It's called a variable crystal oscillator or VXO. You're probably using FT-243 crystals, though, and they don't pull very far. I have to say this again: Time to put this thing on the shelf. For the time and trouble you are putting into it you could build a solid-state rig that would put out as much power, have a VFO and not contain life-threatening voltages. 73, "PM" |
"Paul_Morphy" wrote in message ... " I have to say this again: Time to put this thing on the shelf. For the time and trouble you are putting into it you could build a solid-state rig that would put out as much power, have a VFO and not contain life-threatening voltages. 73, "PM" I suggest he put all his radios on a shelf, and get a cell phone. No dangerous RF levels, no deadly voltages... NOT |
"Paul_Morphy" wrote in message ... " I have to say this again: Time to put this thing on the shelf. For the time and trouble you are putting into it you could build a solid-state rig that would put out as much power, have a VFO and not contain life-threatening voltages. 73, "PM" I suggest he put all his radios on a shelf, and get a cell phone. No dangerous RF levels, no deadly voltages... NOT |
" Uncle Peter" wrote in message news:vQnbc.9210$pM1.6556@lakeread06... I suggest he put all his radios on a shelf, and get a cell phone. No dangerous RF levels, no deadly voltages... NOT Gee, Unc, have a tough week? : I don't want him to give up radio, I just don't think an Ameco AC-1 is worth the trouble. I didn't want one when I was 15 and they were new, and I wouldn't waste my time fiddling with one now. 73, "PM" |
" Uncle Peter" wrote in message news:vQnbc.9210$pM1.6556@lakeread06... I suggest he put all his radios on a shelf, and get a cell phone. No dangerous RF levels, no deadly voltages... NOT Gee, Unc, have a tough week? : I don't want him to give up radio, I just don't think an Ameco AC-1 is worth the trouble. I didn't want one when I was 15 and they were new, and I wouldn't waste my time fiddling with one now. 73, "PM" |
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