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Old 3rd Dec 2019, 4:38 pm   #6
orbanp1
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Join Date: Nov 2009
Location: London, Ontario, Canada
Posts: 672
Default Re: Yaesu FT736 internal mic gain adj possible?

Hi Richard,

I guess I did not read carefully enough your note and missed the point that you need more drive only in the SSB mode!

Looking at the diagrams again, the SSB MIC AMP is the circuit made by Q4011 in the block diagram, Q11 in the schematics. It is an LM358 based dual opamp circuit.
It is the first stage, the (a) opamp that gives about 26.6dB gain, the second stage, the (b) circuit is basically a voltage follower.
If anywhere, the first stage is where you would increase the mic gain.
If you need more gain, you could increase R51, from 470k, that would leave the input impedance of the stage the same, which is basically the value of R50 (22k).

I would first verify if you indeed need more gain there or something else is amiss.

Regards, Peter
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