[Elecraft] L34 tweak help

[Rick Shindley]

Thanks to Tom (N0SS) and the others that offered their advice for adjusting
L34.

There is apparently little relative difference between the signal and noise
as the slug in L34 is adjusted. There is a signal peak that typically occurs
about 1T down from the top, but that is unlikely to be the ideal setting for
SSB filter flatness.  Using Spectrogram, I found the ideal setting for my
rig to be somewhere in the center of L34's adjustment range.

Regarding filter flatness--"good" IF filters have ripple amplitudes of less
than a db.  This rig's filter typically has far more than that (mine does,
anyway!) Ripple affects the amount of amplitude and phase distortion in both
the transmit and receive audio. SSB audio is inherently primitive, so few
care about significant IF passband ripple.  (Regarding PSK-31; PSK-31
requires so little bandwidth, passband ripple is far less of an issue.)

One last thing. I am not sure if this has been mentioned before, but there
is a difference in audio fidelity between the speaker jack and the headphone
jack. The latter has a filter that rolls off high frequency audio. The
difference is noticeable when using Spectrogram. Consider using the speaker
jack to drive Spectrogram (keep the volume low) to get a more realistic view
of your rig's filter performance.

Rick KC0OV
(The cover is back on and I'm not messing with it any more!)