[Elecraft] HOW TO GET IMPROVED AUDIO GAIN ON SSB

[Allen C. Ward]

I noticed, over a year ago, the reduced audio for SSB when using the 2.4 =
kHz filter.  I tried all the fixes for gain and checked all stages in =
the K2 and SSB adapter.  Increasing the preamp gain helped but was'nt =
really a cure.  An study of the SSB adapter revealed that T1 and T2, =
used for impedance matching reduced the gain for SSB 4.8 dB below the =
gain when using the standard narrow filter.  T1 has a gain (voltage =
increase) of +9.94 dB, but T2 has a gain reduction of -14.8 dB.  If one =
matched without using T2 an increase of almost 15 dB is possible.  The =
filter in the adapter is bilateral and signal flow is reversed for =
transmission. This uses the primary of T2 for an rf choke.  The simple =
fix was to remove the four turn secondary of T2 and substitute an =
emitter follower for matching.  A 100 pf cap is used for coupling at the =
junction of X7, cp, and cn to the base of the transistor. The follower =
circuit has a 2N3904 with a 2kohm from base to ground a 10kohm from base =
to collector, a 100ohm from collector to +8V , a .01 cap from collector =
to ground for bypassing and a 180ohm from emitter to ground.  The signal =
goes from emitter to C11. That's it.  There is no adjustment.  =
Spectrographs before and after change are identical.  Transmission and =
audio quality is=20
unchanged.  The important change is plenty of audio for SSB and most of =
the time I don't use the preamp anymore. =20
I have been using this setup on #1107 (now with the 100 watt amp) for =
well over a year and always get good audio reports.  Received audio are =
as good or better than my Corsair or my TS-830.  I also built the audio =
filter and that gives a bit more audio.
What this has to do with the thread of low audio and who is right or =
wrong, I don't care!  It worked for me, it's an easy mod and can be =
removed if you don't like it.  I don't have a web page so I can't post =
details.  Maybe someone else would care to do that.
Try it, maybe you'll like it.

Allen KA5N  k2 #1107


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