[TowerTalk] Broadcast Band AM Transmiiter Intererence on 160M

[Jim Brown]

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