[R-390] Better BA sound - CORRECTED line level tap schematic

[Charles Steinmetz]

I got my nanos and picos scrambled when I transcribed the schematic I 
posted for the Diode Load line-level audio tap.  The shunt capacitor 
(C1) should be 10 NANOfarads (0.01uF), NOT 10 PICOfarads as I had drawn 
it.  While I was at it, I made a few other clarifying edits.

With 10nF, any residual 455kHz IF component is attenuated by ~60dB to 
prevent it causing any mischief in the external audio chain.  IF 
harmonics are attenuated even more.

As noted, the value of R1 is not at all critical -- anything from 10k to 
100k should work fine.  I tend to favor lower values because they reduce 
the susceptibility to noise (both thermal and induced).

Best regards,

Charles


On 1/12/2018 12:58 AM, Charles Steinmetz wrote:
> By far the easiest way to get good sound out of the 390A is to tap
> line-level audio from "Diode Load" Terminal TB103 - 14 at the back of
> the radio and send it to the audio amplifier and speaker of your choice
> (see attached image for tap details).



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