I wonder if Lou Franklin copied channel guard from there or they did from Lou 
Mike
Mike
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Schottkey diode/transistor opinions
- Thread starter Hawkeye351
- Start date
Hawkeye, what you are experiencing is common with this and similar board designs.
The info im giving you came from a Galaxy factory tech many years ago.
the symptom is a very noisy receiver that will exhibit an S meter deflection even with no antenna connected.
the problem is the antenna coil, the one right before the Rf amp transistor.
in your radio this is L6.
the cure is to do the receiver alignment like normal, then unhook everything from the antenna jack on the radio.
radio on, RF gain at max, volume up. AM mode.
de-tune L6 just a bit and the noise will fall right off. it won't take much adjustment.
now you can check your work by putting the sig gen back into the radio so you can see how much sensitivity you lost. it won't be much at all, and once someone connects an antenna to the radio that brings in atmospheric noise, it won't matter at all.
give it a shot and let us know what you think.
LC
The info im giving you came from a Galaxy factory tech many years ago.
the symptom is a very noisy receiver that will exhibit an S meter deflection even with no antenna connected.
the problem is the antenna coil, the one right before the Rf amp transistor.
in your radio this is L6.
the cure is to do the receiver alignment like normal, then unhook everything from the antenna jack on the radio.
radio on, RF gain at max, volume up. AM mode.
de-tune L6 just a bit and the noise will fall right off. it won't take much adjustment.
now you can check your work by putting the sig gen back into the radio so you can see how much sensitivity you lost. it won't be much at all, and once someone connects an antenna to the radio that brings in atmospheric noise, it won't matter at all.
give it a shot and let us know what you think.
LC
Mike, what radio is that with the dual gate mosfet front end?
Brandon, dual gate mosfet front ends were the dream for many people about 20 years ago or so and there was a guy named Bill Good who designed a way to mod the 148gtl/2000gtl to use one.
I never saw one but apparently it worked very well. There's probably still a few out there in the wild.
also, there was a member here years ago that went by CBphreaker, and he made a mod for the AM detector that used an op amp. you can probably find it by searching through his old posts. i built one and it worked well but i ended up removing it from the radio at some point and i can't even remember why now lol.
you seem like someone who might find this interesting.
LC
Brandon, dual gate mosfet front ends were the dream for many people about 20 years ago or so and there was a guy named Bill Good who designed a way to mod the 148gtl/2000gtl to use one.
I never saw one but apparently it worked very well. There's probably still a few out there in the wild.
also, there was a member here years ago that went by CBphreaker, and he made a mod for the AM detector that used an op amp. you can probably find it by searching through his old posts. i built one and it worked well but i ended up removing it from the radio at some point and i can't even remember why now lol.
you seem like someone who might find this interesting.
LC
That schematic is from the DNT Traffic 1. The other DNT radios (at least the ones with a schematic on CBTricks) also used dual gate mosfets.
edit to remove pic. It's available on cbradio.nl, and radiomuseum.org has an internal pic too.
edit to remove pic. It's available on cbradio.nl, and radiomuseum.org has an internal pic too.
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Ok,
I been super busy but I found this very old thread, it is littered with bantering back and forth but contains some really deep digging into the 2n2999 / diode mods.
If you can stand digging through it to find the nuggets.
It started with how to do the mod them progressed
73
Jeff