I'm planning on filling all the 6 MHz filter slots on my Omni V with the TT
filters (1.8 kHz , 500 Hz (already have it) and 250 Hz). I'm looking for
suggestions as to which filter to use in the NARROW slot.
I want to operate both SSB and CW. I'm not that interested in RTTY so I
think I can rule out that filter. What I don't completely understand is how
the NARROW filter interacts with the other filter as far as PBT goes. My
Kenwood TS940 has similarly cascaded filters, but the pass band of each
filter can be shifted. As I understand the Omni V, only the 6 MHz passband
can be shifted.
So, as I see it, if I install a 500 Hz filter centered on 600 Hz (for
discussion let's assume that the filter is perfect so the passband is 350 -
850 Hz) , by varying the 6 MHz PBT, I could shift the 6 MHz filter down to
where it's low pass was 600 (below that, I would lose my desired signal),
giving me an effective passband of 350 - 600 Hz, or I could shift the 6 MHz
filter up to where it's high pass was 600 (again, above that I would lose
the desired signal), giving me an effect passband of 600 - 850 Hz. With this
arrangement, it seems that there is no way to narrow the passband below 250
Hz, and in practicality, I wouldn't quite get to 600 Hz as that would
attenuate the desired signal so the minimum passband will be 300 Hz or so.
Of course, I can get a 250 Hz passband with just the 250 Hz filter.
Since I can get the 250 Hz passband with a 6 MHz filter, would a 1.8 kHz
filter in the NARROW position make more sense, allowing me to improve SSB
readability in the presence of QRM?
73 and thanks in advance for any suggestions,
Mark
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