One of the variable-passband filters we've been considering is one for
SSB, with a range of about 1.4 to 2.2 kHz. It would have 5 poles rather
than 8, but I'm sure it would work well in combination with the I.F.
DSP. The MCU would automatically dial in the crystal filter bandwidth
to match the DSP.
This would be a slot-saver for those want multiple SSB RX bandwidths.
Once the CW variable-passband filter was also ready, you might have:
FL1 6.0 kHz
FL2 2.7 or 2.8 kHz
FL3 1.4-2.2 kHz (SSB variable passband crystal filter)
FL4 0.4-0.8 kHz (CW variable passband crystal filter)
FL5 200 Hz
Variable filters covering a wide range will have slightly greater
ripple than fixed filters when they approach either end of their range,
so we'd only use them in receive mode. In the example above, FL2 would
be used for SSB/CW/DATA transmit and FL1 for AM transmit. Those who
wanted FM and were less concerned about the narrowest possible CW/DATA
bandwidths could shift all of the filters down one slot, bumping out
the 200-Hz filter.
73,
Wayne
N6KR
On Nov 19, 2007, at 11:37 AM, Ed Muns wrote:
If there were a 1.5kHz filter available, I might consider it....
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