[TenTec] Redesigning the filter section of the Orion IF

[Bill Tippett]

Hi Rick,

NJ0IP wrote:
 >Lee, the configuration I described as my preferable configuration is exactly
what Bill, W4ZV told us to do.  (That's why I said do as Bill says, not as
he does.  Bill doesn't work much SSB).  I still operate too much SSB to
eliminate the 1.8 kHz filter.  Sometimes here on our tiny little EU 40m
band, I just lock the roofing filter in at 1.8.

         I've been away camping a few days and this whole discussion
caused me to rethink how I plan to configure my Orion filters.
I now plan to do exactly as you suggested...600 Hz in the 1000
slot and 1800 Hz in the 1800 slot.  My original reasoning in
keeping the 1000 was for casual CW use when I want to scan the
band quickly, but there is no reason that the 1800 would not
work just fine for that.  From my recollection of Sherwood's
measurements, the 1800 has quite good IMD performance and of
course it has a much better shape factor than the 4-pole 1000,
so is should work fine for casual CW (say above DSP = 750 Hz)
where it would be engaged in Filter > Auto.  I'll also move my
1000 Hz filter to the disabled 500 slot for storage.

         BTW, I also still have my 250 Hz and agree with you about
its performance.  Because its insertion loss is a much better
match for the 12 dB gain of the second amplifier, it works
better than the 500 Hz which is overcompensated.  You can also
see this in YT1NT's measurements in the bottom table on page 5
here:

http://www.geocities.com/va3ttn/UsingOrionRX.pdf

Of course in a CW contest, I would likely disable the 250 in
favor of using the 600's excellent IMD performance for DSP = 750
and lower.

                                         73,  Bill  W4ZV