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#1
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Impedance mismatch affecting sideband?
While I solved one problem on SSB, another continues.
I am still having that "carrier" problem on SSB. For some reason, as soon as I speak into the mic, the radio holds power, as if it were on AM. The TX meter on the radio shows this, and the SWR/power meter shows this. The power is not fluctuating with modulation. The ALC was not cranked up. The power is not high, about 20 watts peak. Like I said, it seems to do this as soon as I speak into the mic. Even a subtle noise will send it to max, and stay there. Changed mics, and have the same problem. So then I tried this. I took this radio and put it in my car (it's my only radio). When I connect it directly to the Wilson 1000 barefoot, I get the same problem on SSB. However, when I go thru the amp, it works perfectly, no power unless I modulate. This is also true if the amp is turned on or off. It appears to be an impedance mismatch. Since the amp input is a perfect match, the problem goes away, whether or not the amp power is on or off. Here is the kicker. The SWR on my home antenna is about 1.3-1.5 across the band. Any suggestions? Vinnie S. |
#2
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On Tue, 15 Feb 2005 09:57:06 -0500, Vinnie S. wrote:
Any suggestions? Well, Dave Hall nailed it. It is oscillation. It goes away when the top cover is removed. Now I need a solution. Vinnie S. |
#3
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On Tue, 15 Feb 2005 09:57:06 -0500, Vinnie S.
wrote: While I solved one problem on SSB, another continues. I am still having that "carrier" problem on SSB. For some reason, as soon as I speak into the mic, the radio holds power, as if it were on AM. The TX meter on the radio shows this, and the SWR/power meter shows this. The power is not fluctuating with modulation. The ALC was not cranked up. The power is not high, about 20 watts peak. Like I said, it seems to do this as soon as I speak into the mic. Even a subtle noise will send it to max, and stay there. Changed mics, and have the same problem. So then I tried this. I took this radio and put it in my car (it's my only radio). When I connect it directly to the Wilson 1000 barefoot, I get the same problem on SSB. However, when I go thru the amp, it works perfectly, no power unless I modulate. This is also true if the amp is turned on or off. It appears to be an impedance mismatch. Since the amp input is a perfect match, the problem goes away, whether or not the amp power is on or off. Here is the kicker. The SWR on my home antenna is about 1.3-1.5 across the band. The final oscillation is most definitely related to output load impedance. When I first stumbled onto this problem (In some older dual final Galaxy radios), the problem would never show up on the bench when I used my dummy load. It also didn't show on my base antenna. But the problem would happen on the customer's antenna. I managed to force the problem on my antenna by using a tuner and de-tuning the match until the oscillation occurred. The cover of the radio acts like a capacitor, and it's very sensitive to it. Did you see any bottom mounted caps connected to the final transistor? If not then you might have to mount a piece of grounded shield plate over the final or experiment with bypass caps until you kill the oscillation. But try setting the bias first. If I remember right, the bias for the final should be set at somewhere in the 30 - 40 mA range. I'll check the manual and give you the exact value. Dave "Sandbagger" |
#4
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"Dave Hall" wrote in message ... On Tue, 15 Feb 2005 09:57:06 -0500, Vinnie S. wrote: While I solved one problem on SSB, another continues. I am still having that "carrier" problem on SSB. For some reason, as soon as I speak into the mic, the radio holds power, as if it were on AM. The TX meter on the radio shows this, and the SWR/power meter shows this. The power is not fluctuating with modulation. The ALC was not cranked up. The power is not high, about 20 watts peak. Like I said, it seems to do this as soon as I speak into the mic. Even a subtle noise will send it to max, and stay there. Changed mics, and have the same problem. So then I tried this. I took this radio and put it in my car (it's my only radio). When I connect it directly to the Wilson 1000 barefoot, I get the same problem on SSB. However, when I go thru the amp, it works perfectly, no power unless I modulate. This is also true if the amp is turned on or off. It appears to be an impedance mismatch. Since the amp input is a perfect match, the problem goes away, whether or not the amp power is on or off. Here is the kicker. The SWR on my home antenna is about 1.3-1.5 across the band. The final oscillation is most definitely related to output load impedance. When I first stumbled onto this problem (In some older dual final Galaxy radios), the problem would never show up on the bench when I used my dummy load. It also didn't show on my base antenna. But the problem would happen on the customer's antenna. I managed to force the problem on my antenna by using a tuner and de-tuning the match until the oscillation occurred. The cover of the radio acts like a capacitor, and it's very sensitive to it. Did you see any bottom mounted caps connected to the final transistor? If not then you might have to mount a piece of grounded shield plate over the final or experiment with bypass caps until you kill the oscillation. But try setting the bias first. If I remember right, the bias for the final should be set at somewhere in the 30 - 40 mA range. I'll check the manual and give you the exact value. Dave "Sandbagger" I kinda figured oscillation also. Bad bias can cause it. Make sure that's correct. See if any one had hinkeyed around in there, Check serial numbers, did these not use 2 different finals at different times? When changing finals did they change drive components? Unfortunately I do not have a schematic here to look around. Did anyone do any "coil spreading"? Chad |
#5
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Chad Wahls wrote:
"Dave Hall" wrote in message ... On Tue, 15 Feb 2005 09:57:06 -0500, Vinnie S. wrote: While I solved one problem on SSB, another continues. I am still having that "carrier" problem on SSB. For some reason, as soon as I speak into the mic, the radio holds power, as if it were on AM. The TX meter on the radio shows this, and the SWR/power meter shows this. The power is not fluctuating with modulation. The ALC was not cranked up. The power is not high, about 20 watts peak. Like I said, it seems to do this as soon as I speak into the mic. Even a subtle noise will send it to max, and stay there. Changed mics, and have the same problem. So then I tried this. I took this radio and put it in my car (it's my only radio). When I connect it directly to the Wilson 1000 barefoot, I get the same problem on SSB. However, when I go thru the amp, it works perfectly, no power unless I modulate. This is also true if the amp is turned on or off. It appears to be an impedance mismatch. Since the amp input is a perfect match, the problem goes away, whether or not the amp power is on or off. Here is the kicker. The SWR on my home antenna is about 1.3-1.5 across the band. The final oscillation is most definitely related to output load impedance. When I first stumbled onto this problem (In some older dual final Galaxy radios), the problem would never show up on the bench when I used my dummy load. It also didn't show on my base antenna. But the problem would happen on the customer's antenna. I managed to force the problem on my antenna by using a tuner and de-tuning the match until the oscillation occurred. The cover of the radio acts like a capacitor, and it's very sensitive to it. Did you see any bottom mounted caps connected to the final transistor? If not then you might have to mount a piece of grounded shield plate over the final or experiment with bypass caps until you kill the oscillation. But try setting the bias first. If I remember right, the bias for the final should be set at somewhere in the 30 - 40 mA range. I'll check the manual and give you the exact value. Dave "Sandbagger" I kinda figured oscillation also. Bad bias can cause it. Make sure that's correct. See if any one had hinkeyed around in there, Check serial numbers, did these not use 2 different finals at different times? When changing finals did they change drive components? Unfortunately I do not have a schematic here to look around. Did anyone do any "coil spreading"? Chad LOL "coil spreading". See this is exatcly what I was talking about. Someone is ALWAYS inside a keyclown radio to try and get it to do more power, more channels. The result is all kinds of problems. You would never have these problems if you ran legal gear. |
#6
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"No I Am Not Him" wrote in message oups.com... Chad Wahls wrote: "Dave Hall" wrote in message ... On Tue, 15 Feb 2005 09:57:06 -0500, Vinnie S. wrote: While I solved one problem on SSB, another continues. I am still having that "carrier" problem on SSB. For some reason, as soon as I speak into the mic, the radio holds power, as if it were on AM. The TX meter on the radio shows this, and the SWR/power meter shows this. The power is not fluctuating with modulation. The ALC was not cranked up. The power is not high, about 20 watts peak. Like I said, it seems to do this as soon as I speak into the mic. Even a subtle noise will send it to max, and stay there. Changed mics, and have the same problem. So then I tried this. I took this radio and put it in my car (it's my only radio). When I connect it directly to the Wilson 1000 barefoot, I get the same problem on SSB. However, when I go thru the amp, it works perfectly, no power unless I modulate. This is also true if the amp is turned on or off. It appears to be an impedance mismatch. Since the amp input is a perfect match, the problem goes away, whether or not the amp power is on or off. Here is the kicker. The SWR on my home antenna is about 1.3-1.5 across the band. The final oscillation is most definitely related to output load impedance. When I first stumbled onto this problem (In some older dual final Galaxy radios), the problem would never show up on the bench when I used my dummy load. It also didn't show on my base antenna. But the problem would happen on the customer's antenna. I managed to force the problem on my antenna by using a tuner and de-tuning the match until the oscillation occurred. The cover of the radio acts like a capacitor, and it's very sensitive to it. Did you see any bottom mounted caps connected to the final transistor? If not then you might have to mount a piece of grounded shield plate over the final or experiment with bypass caps until you kill the oscillation. But try setting the bias first. If I remember right, the bias for the final should be set at somewhere in the 30 - 40 mA range. I'll check the manual and give you the exact value. Dave "Sandbagger" I kinda figured oscillation also. Bad bias can cause it. Make sure that's correct. See if any one had hinkeyed around in there, Check serial numbers, did these not use 2 different finals at different times? When changing finals did they change drive components? Unfortunately I do not have a schematic here to look around. Did anyone do any "coil spreading"? Chad LOL "coil spreading". See this is exatcly what I was talking about. Someone is ALWAYS inside a keyclown radio to try and get it to do more power, more channels. The result is all kinds of problems. You would never have these problems if you ran legal gear. But hey it makes more power!!!!! (right where you don't want it) sometimes even lessens the fundamental freq output, but hey it looks good on a meter. (sound of head hitting desk) I also forgot to mention looking for grounding problems internally, Check all points where the circuit board would ground to the chassis. If it was used mobile they may have worked loose/corroded. Pull those screws out, clean with deoxit and reassemble. Chad |
#7
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On 15 Feb 2005 11:42:41 -0800, "No I Am Not Him"
wrote: Chad Wahls wrote: "Dave Hall" wrote in message ... On Tue, 15 Feb 2005 09:57:06 -0500, Vinnie S. wrote: While I solved one problem on SSB, another continues. I am still having that "carrier" problem on SSB. For some reason, as soon as I speak into the mic, the radio holds power, as if it were on AM. The TX meter on the radio shows this, and the SWR/power meter shows this. The power is not fluctuating with modulation. The ALC was not cranked up. The power is not high, about 20 watts peak. Like I said, it seems to do this as soon as I speak into the mic. Even a subtle noise will send it to max, and stay there. Changed mics, and have the same problem. So then I tried this. I took this radio and put it in my car (it's my only radio). When I connect it directly to the Wilson 1000 barefoot, I get the same problem on SSB. However, when I go thru the amp, it works perfectly, no power unless I modulate. This is also true if the amp is turned on or off. It appears to be an impedance mismatch. Since the amp input is a perfect match, the problem goes away, whether or not the amp power is on or off. Here is the kicker. The SWR on my home antenna is about 1.3-1.5 across the band. The final oscillation is most definitely related to output load impedance. When I first stumbled onto this problem (In some older dual final Galaxy radios), the problem would never show up on the bench when I used my dummy load. It also didn't show on my base antenna. But the problem would happen on the customer's antenna. I managed to force the problem on my antenna by using a tuner and de-tuning the match until the oscillation occurred. The cover of the radio acts like a capacitor, and it's very sensitive to it. Did you see any bottom mounted caps connected to the final transistor? If not then you might have to mount a piece of grounded shield plate over the final or experiment with bypass caps until you kill the oscillation. But try setting the bias first. If I remember right, the bias for the final should be set at somewhere in the 30 - 40 mA range. I'll check the manual and give you the exact value. Dave "Sandbagger" I kinda figured oscillation also. Bad bias can cause it. Make sure that's correct. See if any one had hinkeyed around in there, Check serial numbers, did these not use 2 different finals at different times? When changing finals did they change drive components? Unfortunately I do not have a schematic here to look around. Did anyone do any "coil spreading"? Chad LOL "coil spreading". See this is exatcly what I was talking about. Someone is ALWAYS inside a keyclown radio to try and get it to do more power, more channels. The result is all kinds of problems. You would never have these problems if you ran legal gear. Thats why they moved the capacitors to the bottom of the radio, more room to spread the coils. |
#8
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"Lancer" wrote in message ... On 15 Feb 2005 11:42:41 -0800, "No I Am Not Him" wrote: Chad Wahls wrote: "Dave Hall" wrote in message ... On Tue, 15 Feb 2005 09:57:06 -0500, Vinnie S. wrote: While I solved one problem on SSB, another continues. I am still having that "carrier" problem on SSB. For some reason, as soon as I speak into the mic, the radio holds power, as if it were on AM. The TX meter on the radio shows this, and the SWR/power meter shows this. The power is not fluctuating with modulation. The ALC was not cranked up. The power is not high, about 20 watts peak. Like I said, it seems to do this as soon as I speak into the mic. Even a subtle noise will send it to max, and stay there. Changed mics, and have the same problem. So then I tried this. I took this radio and put it in my car (it's my only radio). When I connect it directly to the Wilson 1000 barefoot, I get the same problem on SSB. However, when I go thru the amp, it works perfectly, no power unless I modulate. This is also true if the amp is turned on or off. It appears to be an impedance mismatch. Since the amp input is a perfect match, the problem goes away, whether or not the amp power is on or off. Here is the kicker. The SWR on my home antenna is about 1.3-1.5 across the band. The final oscillation is most definitely related to output load impedance. When I first stumbled onto this problem (In some older dual final Galaxy radios), the problem would never show up on the bench when I used my dummy load. It also didn't show on my base antenna. But the problem would happen on the customer's antenna. I managed to force the problem on my antenna by using a tuner and de-tuning the match until the oscillation occurred. The cover of the radio acts like a capacitor, and it's very sensitive to it. Did you see any bottom mounted caps connected to the final transistor? If not then you might have to mount a piece of grounded shield plate over the final or experiment with bypass caps until you kill the oscillation. But try setting the bias first. If I remember right, the bias for the final should be set at somewhere in the 30 - 40 mA range. I'll check the manual and give you the exact value. Dave "Sandbagger" I kinda figured oscillation also. Bad bias can cause it. Make sure that's correct. See if any one had hinkeyed around in there, Check serial numbers, did these not use 2 different finals at different times? When changing finals did they change drive components? Unfortunately I do not have a schematic here to look around. Did anyone do any "coil spreading"? Chad LOL "coil spreading". See this is exatcly what I was talking about. Someone is ALWAYS inside a keyclown radio to try and get it to do more power, more channels. The result is all kinds of problems. You would never have these problems if you ran legal gear. Thats why they moved the capacitors to the bottom of the radio, more room to spread the coils. Good one! First laugh I've had here in a while! Chad |
#9
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On Tue, 15 Feb 2005 13:36:32 -0600, "Chad Wahls"
wrote: Did you see any bottom mounted caps connected to the final transistor? If not then you might have to mount a piece of grounded shield plate over the final or experiment with bypass caps until you kill the oscillation. But try setting the bias first. If I remember right, the bias for the final should be set at somewhere in the 30 - 40 mA range. I'll check the manual and give you the exact value. Dave "Sandbagger" I kinda figured oscillation also. Bad bias can cause it. Make sure that's correct. See if any one had hinkeyed around in there, Check serial numbers, did these not use 2 different finals at different times? When changing finals did they change drive components? Unfortunately I do not have a schematic here to look around. Did anyone do any "coil spreading"? I checked the factory service manual last night. They recommend setting both the driver and final bias to 50 mA. That seems a bit high, as the driver stages in many other radios are set around 40 mA. My 2510 is set to factory specs and I've never added any "mods" to it, and it doesn't oscillate. Dave "Sandbagger" |
#10
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On Wed, 16 Feb 2005 08:08:36 -0500, Dave Hall wrote:
On Tue, 15 Feb 2005 13:36:32 -0600, "Chad Wahls" wrote: Did you see any bottom mounted caps connected to the final transistor? If not then you might have to mount a piece of grounded shield plate over the final or experiment with bypass caps until you kill the oscillation. But try setting the bias first. If I remember right, the bias for the final should be set at somewhere in the 30 - 40 mA range. I'll check the manual and give you the exact value. Dave "Sandbagger" I kinda figured oscillation also. Bad bias can cause it. Make sure that's correct. See if any one had hinkeyed around in there, Check serial numbers, did these not use 2 different finals at different times? When changing finals did they change drive components? Unfortunately I do not have a schematic here to look around. Did anyone do any "coil spreading"? I checked the factory service manual last night. They recommend setting both the driver and final bias to 50 mA. That seems a bit high, as the driver stages in many other radios are set around 40 mA. My 2510 is set to factory specs and I've never added any "mods" to it, and it doesn't oscillate. Dave "Sandbagger" I need a DMM that measures current. any recommendations on one that is good, without breaking the bank? The Flukes run abour $150 on ebay. I didn't want to spend that much. Vinnie S. |
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