> The station at 1.46 MHz is very close to 1.8 MHz and 30 dB of rejection on
> a high pass filter would be tough (but not impossible) to design and
> duplicate. Perhaps a notch filter is in order since it is only a discrete
> frequency you are trying to reject.
It is difficult to obtain high rejection at 1.5 MHz and have low loss and
reasonable ripple above 1.8MHz. Most filter attenuation or ripple won't
measure nearly as good as "calculated" through tables or software because of
component tolerances and Q limits. Shielding is probably the least worry on
160, as long as there is a good groundplane and there are no ground loops in
or around the filter.
The best solution would be normal filter with an additional a
series-resonant trap from input to ground tuned to 1.46 MHz. You could use
two traps, one at each end of a filter. The inductor would have to be
parallel tuned at 1.8, and the resonant parallel L/C combination on 1.8
series tuned to ground on 1.46. The L should be fairly low value and C high
value.
The MFJ filter would only give about 30dB, but that might be enough. You
could always try one and if it didn't work return it.
73 Tom
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