I should have also said that any of the 6.3 MHz IF filters are
compatible with the "lowered tone " filter, because all you have to do
is adjust the PBT to make the bandpass of the 6.3 MHz IF coincident with
that of the 9 MHz IF. Also the Inrad 765 is the most similar filter to
the Ten-Tec 221 as far as center frequency and bandwidth is concerned.
When it comes to the question of which other 9 MHz filters are
"compatible" with either the Ten-Tec 221 or Inrad 765, that really
depends on what you mean by compatible. Neither Ten-Ten nor Inrad makes
a slightly wider bandwidth filter that is also centered on the same
frequency as the 221 or 765. All of their 9 MHz filters that are wider
are also centered at higher frequencies, and have various degrees of
overlap with the bandpass of the 221 or 765.
I spent some time with some graph paper, drawing all the various filter
bandpasses from 9.000 to 9.300 MHz to see how they all compare, and how
they might work together. I would suggest you try this yourself. That is
probably a good way to predict what you would like in filter selections,
although when you try it you may find your prediction was not absolutely
correct. I suspect this is why we see so much filter swapping traffic on
this reflector.
I'd love to see an after market 9MHz IF board for the Omni VI with room
for more filters.
DE N6KB
3) If I were able to find the special N4PY "lowered tone" CW filter, what
other set of CW filters should I buy that are compatible with it?
The "low note CW filter" for the Omni VI is the Ten-Tec model 221. It is
specified as 250 Hz bandwidth, centered on 9.000500 MHz, which will
result in a 500 Hz tone when the BFO is set to 9.00000 MHz as it should
be in CW mode. Ten-Tec does not list these as an available item any
more. I got mine through this reflector.
4) In addition to crystal filters, s
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