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@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
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