Hi Jon,
an 8-pole 6.3 MHz filter.
It sounds like an SSB filter, narrower than the regular one, BUT,
instead of chopping up the higher tones, it chops down the lower
tones.
You didn't say what radio you are using it in. If it is in an Omni VI,
whether it passes more high tones or low tones depends not only on the
center frequency of the 6.3 MHz IF filter. It also depends on the
setting of the PBT, and the alignment of C24 and R18 on the Passband
Tuning Board. Maybe it is just a plain model 288, 1.8 kHz filter. (I am
guessing that a 288 is an 8 pole filter. My only printed reference does
not say, and I'm not opening up the rig right now to look.) You should
be able to adjust the PBT control to hear lower tones. If you have a
narrow filter in the 9 MHz IF, you may be limited by it too. Try
switching the NAR (or N-1 and N-2) filter out, and twiddling the PBT knob.
DE N6KB
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