[TowerTalk] Broadcast Band Filter

[Jim Brown]

On 3/26/2020 9:16 PM, Mike Ryan wrote:
> I remember someone recommending a brick wall AM broadcast band filter some
> months back.  Was a little on the expensive side but.if it works.  Anyone
> recall that thread and the name and/or contact for the manufacturer or
> dealer? 

I checked into those that were mentioned in that thread, and came to the 
conclusion that the one that DX Eng sells looked like best or close. 
Also, the better bandpass filter sets are pretty good at killing the AM 
BC band. Even the 160M filters in the better sets are 25-30 dB down or 
so at about 1.3 MHz, get better as they go lower in frequency. Filters 
for the higher bands are more like 50 dB down on the entire AM band. If 
your problem is 160M and the interference is high in the band, you'll 
likely need the dedicated BCB filter.

The link below is a report I prepared for National Contest Journal 
several years ago on filters that were then available for me to measure. 
At the end of the report is a link to a page of links to individual 
measurements for each filter on each band.

http://k9yc.com/BandpassFilterSurvey.pdf

I recently acquired a pair of FilterMax IV filter sets, and measured 
them. They are in a league with the best I measured for the report, and 
in some cases better. I think Array Solutions sells them.

Note also that if your rig allows you to patch the filter into the RX 
line on the RX side of the TX/RX switching, you don't need a filter 
rated for transmitting.

73, Jim K9YC