Topband: AM Broadcast Filter recommendation

[Chris G3SVL]

Hi Steve,

If the problem is the second harmonic then a BCB filter at your end will 
not help because the second harmonic isn't in the Broadcast Band. 
However, I suspect the problem may be blocking of your rx input by the 
fundamental frequency which the filter will address. You don't say what 
the TX power of the BC station is (which would give a clue to the field 
strength you see at your rx antenna). You could try a simple series 
tuned cct, tuned to 910kHz, across your rx input.

I  have a MW transmitter 300m from my antenna. It used to have three MW 
stations combined to produce 2.4kW running 24/7. The worst offender was 
700w on 945kHz (second harmonic 1890kHz). I have an ICE BCB which claims 
to be 60dB down at 900kHz (but installed performance won't be that 
good). Some earlier rigs blocked, but the K3 and FTdx101 cope without 
it. The second harmonic was detectable but as I rarely do SSB and we are 
limited in power above 1850 it didn't really bother me.

Fortunately the gradual decommissioning of AM stations here in the UK 
means it is now a single 400W signal on 693kHz that doesn't bother me.

73 Chris, G3SVL


On 05/12/2023 21:19, Steve Muenich wrote:
> Hi Guys,
>
> I'm looking for a recommendation for an AM Broadcast filter for my receive
> only input.
> Unfortunately I live 2 miles form 910 khz AM so their 2nd harmonic wipes
> out 1820. For the most part I work around it and stay up higher in the band.
> There are other stations in the area of course that I'd like to knock down
> their signal further.
> I'm currently using an older 20+ year old ICE BCB filter that when swept on
> my tracking generator only attenuates -25db at 1700khz. The band would be
> absolutely unuseable without it.
>
> My receive antennas are 4xHi-Z array and a single NE facing beverage
>
> I'm looking for a newer filter that has better performance and
> attenuation below 1800khz.
>
> Any suggestions?
>
> Thanks
> Steve, NA5C
> _________________
> Searchable Archives: http://www.contesting.com/_topband - Topband Reflector