Topband: 160M Bandpass filter drawing. K0FF

[Tom Rauch]

Hi Earl,

> Regarding methods to attenuate strong BC signals when they are a problem
> on 160-meters, perhaps a better method would be to design a notch filter
> tuned to the frequency of the interfering signal.  This would be much
> sharper than a bandpass filter and is certainly conceivable to implement
> if one is using a separate receive antenna.

A notch would be my first reaction also, but the component values 
required are not commonly available when nulling 200 kHz. Also 
padding the trap to frequency would be a "chore".

The most simple approach when components and frequencies are 
considered is a high-pass T, a second option would be a parallel 
network resonant on 160 across the line.  
 
> MFJ effectively uses this method in their MFJ-731 tunable notch filter
> which is sold as an accessory for the MFJ-259B analyzer -- but if you buy
> the MFJ-731 for this purpose don't place it in your transmit antenna coax
> line!

That unit contains a variable notch that covers the AM BCB and a 
parallel tuned circuit.




73, Tom W8JI
w8ji@contesting.com


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