It would seem to me that the best use of the Inrad wide filter would be to
leave the original filter in position one in the first IF. The you could easily
move a few wires to bypass that filter in receive, and go directly to the 2.8
KHz filter in position 2. This is easy because, in the Omni 6, TenTec cascaded
the first filter into the second one. If you use the PIN diodes to go around
the position one filter (2.4 KHz) you would take full advantage of the wider
filter in position two only in receive. In transmit, everything would remain
stock.
Omni 6 radios never sounded all that bad in transmit, only in receive (to my
ears anyway). The above method should improve that sound by quite a bit.
BTW: I never observed any significant improvement in Omni 6 audio on receive
with the so-called audio improvement mod. I have tried it on several Omni 6’s
and never saw much difference.
I believe the filters in the Omni 6 have more in band ripple than they should,
and also the positioning of the first IF filter with respect to the second IF
filter combines to produce the nasal sound of the omni 6 (non-optimal overlap).
No amount of audio chain alteration will correct for that.
I have even taken the audio directly from the product detector and passed this
through to an outboard audio amplifier. No real improvement in audio was
observed.
This supports the notion that the restricted audio arises in the IF combination
of filters and their respective center frequencies and overlap.
The only other place where such restricted frequency response could take place
is in the very first ceramic filter that is used prior to any of the 9 MHz
roofing filters. I have never tried bypassing this just to see what impact it
has on the audio response. I will wait for that until I see how the filter
arrangement in this particular Omni 6+ sounds.
I can’t wait to hear how this Omni sounds tomorrow with the high buck 3.1 KHz
filters in both IF’s. I have high hopes...
Gary
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