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CAT500DX capacitor

 

What value capacitor are some using across the op amp in the CAT500 to deemphasis the audio ? There is a space for one but not used if taking the audio after the deemphasis.

I am interfacing the CAT 500 with a GE MASTR ll and pulling the audio off what would be called the discriminator if it actually had one instead of the IC that does the demodulaing. I played around with it and seems that a .015 uF looks good on a service monitor when I sweep the audio.

Ralph ku4pt
 

Cut and try seems to be what CAT recommended so if you're happy with the result using 0.015 - go with it.

Cat:

"Receiver Audio Response
Each receiver input has a buffer amplifier with a gain of three. The frequency response is flat over a range of 300 to 3000 Hz.
If discriminator audio is being used, it may be necessary to add some high frequency roll off.
Space is provided to install a capacitor across the feedback resistor on each receive audio amplifier.
Start with a .001uF capacitor and increase the value as required."
 

Thanks ,? I saw the part about the gain of three but did not see in my 2 different manuals any starting values.? There is a remote base board that is the same way and all I got from the manual was install and try.? I did put in some pins in the holes so I could use some plug ins to make it easy to change.? I tried a few values and just swept the audio going into the receiver and looked at the deviation on the output to see if it stayed about the same.? Without the capacitor the deviation changes a lot depending on the audio frequency which is what I would expect.
Have not tried it on the air yet.

Ralph ku4pt


On Thursday, September 23, 2021, 04:54:24 PM EDT, nj902 <wb0emu@...> wrote:


Cut and try seems to be what CAT recommended so if you're happy with the result using 0.015 - go with it.

Cat:

"Receiver Audio Response
Each receiver input has a buffer amplifier with a gain of three. The frequency response is flat over a range of 300 to 3000 Hz.
If discriminator audio is being used, it may be necessary to add some high frequency roll off.
Space is provided to install a capacitor across the feedback resistor on each receive audio amplifier.
Start with a .001uF capacitor and increase the value as required."
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