Topband: BCB interference ?

[Jim Brown]

On Mon,9/22/2014 6:50 AM, Ed Stallman wrote:
> Has anyone used this High Pass Filter ? 
> http://www.dunestar.com/store/160-Meter-Highpass-Filter-pid-8.html

The spec for this filter is ambiguous. Is the -40dB at all frequencies 
below 1.6 MHz, or at 1 MHz?  BIG difference. OTOH, the Dunestar filters 
are decent for the price.

>
>  I found I have a 25KW AM 1520 Khz BC transmitter 12 miles from me , 
> is that close enough to interfere with me receiving weak signal DX on 
> the top Band ? I do hear some wide band hash 1837 to 1840 !

That may be because they are transmitting digital radio. No filter will 
remove that -- it's part of their sidebands.

>
> Thought I would asking before placing an order, not sure how what to 
> look for with BCB interference ? 

A year or so ago, I reviewed a bunch of bandpass filter sets designed 
for contesters. I also measured an ICE BCB filter (160M highpass).  
k9yc.com/BandpassFilterSurvey.pdf  The pdf includes a link to pdfs of 
the VNWA data.  I measured the filters that I either owned or could 
borrow from local NCCC members. Sorry -- the ICE BCB was the only one I 
had access to.

I didn't put a marker at 1.5 MHz (I would have, but I was out of 
markers), but eyeballing it without a marker, I'd say that all of these 
filters (except the ICE419Bs) would be down by at least 15 dB at 1.5 
MHz. The ICE BCB was about -16 dB at 1.5 MHz.  15 dB would reduce that 
25kW station to 800W. Maybe enough, maybe not.  For more rejection, 
you'll need one of the W3NQN designs that Array Solutions sells.  And 
remember that NO filter will touch any sideband trash that the station 
puts on 160M.

73, Jim K9YC