On 1/30/2022 1:57 PM, Mike Ryan wrote:
By FAR my greatest offender is at 1420AM which is less than one
mile from my qth.
If you can kill it with a BPF or HPF, they're not the offender, the
preamp is. And with the problem station fairly high in the band, you'll
want a BPF or HPF with pretty steep skirts. Best bet is to study
published curves for stuff from DX Engineering, WX0B, and the filter
mfrs themselves. I remember looking a year or so ago and the state of
the art seemed to be in the range of 40 dB fairly high in the band.
Also, the better BPF sets made for contesting have pretty good
attenuation on the AM BC band. At the end of this report is a link to my
measured data on those that I owned or had loaned to me for measurement.
The report: http://k9yc.com/BandpassFilterSurvey.pdf
The data: http://audiosystemsgroup.com/BandpassFilterData.htm
A few years ago, I acquired a pair of used Hamation FilterMax-IV sets
that measured quite well, but I don't think I saved the data. TXBPF sets
are in my SO2R station, and the Hamation units are on the rig side of
switching for my RX antennas.
Unfortunately I didn't have enough cursors to put one in the AM band,
but an eyeball guestimate is that the better ones will get you 15-20 dB
at 1420. That report includes measurement for a vintage ICE BCB, which
is in that range. As I understand it, Morgan took over that line.
The trap that Jim Lux suggested would probably go a lot lower.
73, Jim K9YC
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