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Changing deadkey???????????
- Thread starter RugRat235
- Start date
That depends on what you mean ? .....not so much on a solid power supply ,in the mobile I've seen a slight change from the car being started from the off position, but very slight at that and more so understandabley why,more solid amps with the motor running. I did have a Grant DX many years ago , it would dead key 6 watts but then the carrier would slowly dissapate down to 0 as you held the PTT down ? ......is this the problem your having ? It's been a good 10 years since I had that perticular problem with that Grant DX and I never did find out what the problem was on that ? .....everything else on that radio seemed to work just great. I have never seen the same problem in any other radio I have owned since then, so I would be curious to know what your problems might be ? something is not holding something here as it should ? Cap ? Resis ? Transis ? Diode ? good luck to you.
Dead key change
I experienced this once with a Galaxy 66 When holding the key down with the amp on you could watch the amps carrier climb. Would be hard to calibrate the swr meter too with amp on. It didn't do it with just radio carrier, only when driving amp. Some say it's common with the NPC mod. With 1x4 pill carrier might creep 25 watts say 200 to 225. Drove me nuts. No more NPC for me. Justin tune only. No it wasn't the coax!!
I experienced this once with a Galaxy 66 When holding the key down with the amp on you could watch the amps carrier climb. Would be hard to calibrate the swr meter too with amp on. It didn't do it with just radio carrier, only when driving amp. Some say it's common with the NPC mod. With 1x4 pill carrier might creep 25 watts say 200 to 225. Drove me nuts. No more NPC for me. Justin tune only. No it wasn't the coax!!
I've seen a lot of Cobra29/Uniden PC-66/68/76/78-type radios with a particular odd habit.
When they remove the jumper wire that feeds modulated power to the driver transistor, a problem arises. One, single disc capacitor to ground is used to filter stray RF from leaking "upstream" from out of BOTH the driver's output circuit AND the final's output circuit. One disc cap to ground (on the frontwards jumper-wire hole) filters (decouples, bypasses) BOTH final and driver stages.
Removing the jumper wire, to insert either a fixed resistor/electrolytic OR a transistor for "variable", now UNHOOKS the bypass capacitor from the driver's output circuit.
Folks who patch a 2-Watt control across the jumper wire's holes in the board, will turn it to get the desired carrier, unhook it and read the pot with an ohmmeter. Then, a fixed resistor close to that value SHOULD give you the same carrier power, right?
The answer is, only sometimes. The "missing" bypass disc cap makes the driver stage unstable. The fix is to add a .02 uf (or so) disc to ground from the rear-most pad where the jumper wire was pulled. Now, the driver has its own bypass cap, and carrier settings will be a lot more stable.
Been waiting for one of the online descriptions of "Put Variable In Your Cobra 29" to include this little detail. Still waiting.
73
When they remove the jumper wire that feeds modulated power to the driver transistor, a problem arises. One, single disc capacitor to ground is used to filter stray RF from leaking "upstream" from out of BOTH the driver's output circuit AND the final's output circuit. One disc cap to ground (on the frontwards jumper-wire hole) filters (decouples, bypasses) BOTH final and driver stages.
Removing the jumper wire, to insert either a fixed resistor/electrolytic OR a transistor for "variable", now UNHOOKS the bypass capacitor from the driver's output circuit.
Folks who patch a 2-Watt control across the jumper wire's holes in the board, will turn it to get the desired carrier, unhook it and read the pot with an ohmmeter. Then, a fixed resistor close to that value SHOULD give you the same carrier power, right?
The answer is, only sometimes. The "missing" bypass disc cap makes the driver stage unstable. The fix is to add a .02 uf (or so) disc to ground from the rear-most pad where the jumper wire was pulled. Now, the driver has its own bypass cap, and carrier settings will be a lot more stable.
Been waiting for one of the online descriptions of "Put Variable In Your Cobra 29" to include this little detail. Still waiting.
73
this is what i posted in another topic about my cobra 200gtl
i noticed something alittle strange with my 200. i had set everything up in the house using my 25 amp power supply and then put the radio out in my truck and rechecked everything. the am deadkey was way higher than i had set it. i thought maybe i was drawing more amperage so reset. next day checked it again to find it lower than i set it the day before. reset but havn't checked again yet. i will later today. maybe this happened to yours also. never heard of a deadkey changing like that?
it seems to change from day to day one day set it at 5 watts low power next day check it and its down to 3 or up to 10. same with the high power deadkey.
nomad that sounds like it might be my problem. i'll have to look into it once i get a chance to bring it back inside. having the 2290 finals the setup is different though.
i noticed something alittle strange with my 200. i had set everything up in the house using my 25 amp power supply and then put the radio out in my truck and rechecked everything. the am deadkey was way higher than i had set it. i thought maybe i was drawing more amperage so reset. next day checked it again to find it lower than i set it the day before. reset but havn't checked again yet. i will later today. maybe this happened to yours also. never heard of a deadkey changing like that?
it seems to change from day to day one day set it at 5 watts low power next day check it and its down to 3 or up to 10. same with the high power deadkey.
nomad that sounds like it might be my problem. i'll have to look into it once i get a chance to bring it back inside. having the 2290 finals the setup is different though.
Thats funny, never heard of nor have any of my NPC modded radios done this. I doubt he did the NPC to his brand new Cobra 200 so there goes that theory I guess. All I know is I ran my NPC Delta Force head to head against a Justin tuned S3 for several hours, I would switch radio's back and fourth with several base stations on the air. They all finally told me to just leave the Delta in line because it was louder, cleaner, and just plain sounded better. To each his own, go with what works for you best there Boomer.
could the cap situation might have been what was wrong with my Grant DX way back youder when ? .....IM not kidding ,dead key 6 and dissapate to 0 ,and yes there was still audio ,just wouldn't hold a dead key ? ......I've thought about that radio over the years ,just never did get a answer on it and why ? (long story)
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@ ButtFuzz:Please advise me to what is a good replacement mic for my SR-497HPC... Answer: 497 is "wired like Cobra", so many choices available. That radio does not need a power mic, so purchase a stock "coffin style" mic with a decent cord, like the ones that Astatic uses. The Superstar DM-507 is my go-to. https://www.ebay.com/itm/3050474478...adANq91JSiEEnz8EGqPJRBloTgEyaVsBoCtoMQAvD_BwE $12.99 + .99 cent shipping.
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