Today I performed a test of the operation of the aforementioned 3.1 KHz first
and second IF SSB filters.
For evaluation I was listening to a station on 20 meters as his audio was not
of the extended SSB variety, he just had pleasing natural sounding audio. His
callsign is not relevant to this discussion.
Using the existing Ten Tec audio line, with both 3.1 KHz filters in place, I
could just tell the difference between the standard Ten Tec SSB filters and the
3.1 KHz filters in terms of pleasant, natural sounding audio. In other words,
those who have mentioned that the restrictive audio in the Omni 6 lies in the
AF stages are partly correct. Whether or not this is correctable remains to be
seen.
However, when I removed the cable from point 54 on the IF/Audio board and fed
its signal into my powered speaker that I have been using for almost a year
with my other station (a Pro 2), the difference in audio performance when
comparing the stock SSB filters with the 3.1 KHz filters is dramatic, very
dramatic. The sound from the stock filters was still quite restricted and
lacking any significant low frequency content regardless of PBT setting. When I
switched in the 3.1 KHz filters, one-at-a-time, the sound completely expanded
to the quality I am accustomed to hearing from my Orion’s. Each filter made it
own contribution to the sound quality.
Thus it would seem that the COMBINATION of audio line frequency limitations AND
the filter limits contribute pretty strongly to the overall audio sound
characteristics produced by the Omni 6.
Please note that this Omni 6+ is pretty late, with the SMD boards in three of
the circuits. Thus it has the last of the various upgrades that Ten Tec did do
over time on this terrific radio.
Now I am torn regarding the future of this radio in my shack. It sounds so good
when set up this way, that I am tempted to make it the primary station (once I
resolve the obvious BFO positioning on the filter edges in transmit).
I have to give up the internal DSP as well, since that contributes quite a bit
to the response limitations, this is well documented in the Ten Tec reflector
archive.
The DSP in this radio is not anything that blows me away anyway so it’s not a
big loss.
I just wanted to close the loop on this topic. Both portions of the radio
contribute to the issue, improving neither by itself will make much difference
in the audio output of this radio, IN MY OPINION and supported by this direct
observation.
I really never believed that an Omni 6 could sound this nice.
Gary
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