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Negative Peak Compression boards for Cobra 29

While you have that thing on your bench, measure the DC component of the JP36.

Then SOLDER a cap across the JP36 where it goes into the Cobra, then do this again.
  • That cap is the missing component of any Swing Mod using the Variable carrier.
  • See post # 80 - (Oh man! this threads gotten long...)
  • - remember the Diode may be a Zener - causing a condition of "quick and fast hold" clamp action - it would explain the ramp you have at the end of the signal. The effect is amplified because the AMC it's self has a Peak and Hold - so you see that trailing slope like those shown on the other shots from the YT bench vids.
 
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Handy Andy said:
While you have that thing on your bench, measure the DC component of the JP36.

Then SOLDER a cap across the JP36 where it goes into the Cobra, then do this again.
  • That cap is the missing component of any Swing Mod using the Variable carrier.
  • See post # 80 - (Oh man! this threads gotten long...)
  • - remember the Diode may be a Zener - causing a condition of "quick and fast hold" clamp action - it would explain the ramp you have at the end of the signal. The effect is amplified because the AMC it's self has a Peak and Hold - so you see that trailing slope like those shown on the other shots from the YT bench vids.
Click to expand...
I just installed a 100 micro farad capacitor across the JP36 wires. It doesn't seem to have made any difference. It still has the funny flat bottom DC levels.
 
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Shadetree Mechanic said:
Forgot all about this diode mod until it popped up in another thread. Has anyone tried it?
Click to expand...

I've had fixed a lot of bad caps on radios that use this mod

I've had to take and fix regulator issues due to the problems it can cause.

The thing multiplies voltage - careful on this because people tend to "volt up" radios - which adds to this effect.

Can damage VCO/PLL due to spikes the thing can make.

This Diode mod Reminds me of the "fine print" in those "contracts" during a Job interview...
"This list is incomplete and will be supplemented as necessary"

​
 
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