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Re: Preamp question


 

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Just reduces the gain.? See the data sheet for the part.? They explain it there.

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From: [email protected] [mailto:[email protected]] On Behalf Of Woody
Sent: Tuesday, November 27, 2018 1:54 PM
To: [email protected]
Subject: [BITX20] Preamp question

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Now that Raduino working, still trying to resolve RX issues.?? There is so much clock signal floating around that it masks the RX signal when I try to trace with scope.? So...

Now trying a brute force approaches to low RF sensitivity and low, distorted audio.? They sort of work...

Audio:
Bypassed board audio amp section and used a LM358 to feed the audio PA IC.? Much improved, but does want to oscillate if gain set too high.

RF:
Built a MMIC front end amp.? I can now hear noise when I connect the antenna!? Signals notably stronger.
Would like to add a RF gain control.? Found that controlling the voltage to the MMIC (thus the current), the gain will change from maximum to a very low value, perhaps even attenuating the signal.

Here is my question:
What are any negative effects of operating the MMIC at currents much lower than specified?
Thanks, Woody? -? KZ4AK


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