Our club's Omni6+ option3 sounds very different on USB and LSB, and it's
not possible to correct it by adjusting the BFO frequencies, so it must be
down to the filter being asymetrical. I understood that was a common
failing, but perhaps our filter is faulty?
As is I recall, my Omni Six resulted in upward passband shift in USB, which
result in "thinner' audio with less low-end audio content. To localize it
to the filter, bypass the 2.4K filter with a wire will and the likely result
is audio that is equal in response on both USB and LSB.
The INRAD 2.8K filter in the 2.4k @ 9MHz slot will result in better SSB
symmetry between LSB and USB, and may in fact clean up the transmitted CW
since the CW TX BFO frequency is shifted further away from the knee of the
filter. The introduction of the INRAD 2.8K filter was a joint effort
between myself and W2VJN to assist with the Omni Six's transmitted CW issue.
The secondary benefit was better SSB audio quality.
Paul, W9AC
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