[TowerTalk] Broadcast Band Filter

[Michael Tope]

A very good way to check for this is to put an attenuator (10 to 20dB) 
between the radio and the antenna which is picking up the sort of 
bleed-through Mike describes. If the bleed-through doesn't go away when 
you add-in the external attenuation, the problem is likely NOT in the 
radio. Switching in the radio's internal front-end attenuation isn't 
always sufficient. I had a case where the bias on the PIN diodes that 
switched high-pass filters into the receiver front-end of one of my 
radios was being modulated by the very strong BCI from a nearby 4-tower 
array that favored me more during the day. Switching in the radio's 
front-end attenuation didn't help. I had to attenuate the signal ahead 
of that PIN diode switched filter-bank in order to reduce the bleed 
through.  When I did that, the bleed-through stopped, so I knew the QRM 
was being generated inside the radio.

73, Mike W4EF.........


On 2/27/2024 10:47 AM, john at kk9a.com wrote:
> I have no filter suggestions but just be aware if the interference is from
> rectification at your station, filters will not help.
>
> John KK9A
>
> From:	"Mike Ryan" K4CVL wrote:
>
> During the last 160m SSB contest it became obvious that I am in need of a
> serious broadcast band filter.  Though I currently have one in-line that I
> bought a dozen years ago (cannot recall what brand) I appear to be getting
> some bleed through from 1420 AM. If only it were good music, or even bad
> music. But the 'fire and brimstone' programs and subject matter are more
> than I can take. Suggestions?  - Mike, K4CVL
>
>
> _