Topband: Hi-Pass filter for 160 to reject BC Band

[Roger Parsons]

Eddy VE3CUI wrote:

>Hi George,
>
>I'm curious as to how the results might compare, if one were to simply place a 
>series-connected coil & capacitor wave trap (resonant to the BC station's 
>frequency, of course) to ground at the receiver input...? Was that tried prior 
>to the inclusion of the high-pass filter?
>
>The wave trap could be made even more effective if one were to place a second 
>parallel-tuned trap in series with the antenna lead, and installed between the 
>receiver & the series-tuned trap...
>
>~73~ de Eddy VE3CUI - VE3XZ

Hi Eddy

You are correct, but obviously this is not the best approach for multiple broadcast stations.

When I first built my remote station there was a high power AM station with an 8 element
array beaming straight at it from about 1km away. This made receiving difficult as it was 

inducing literally volts onto my 260' vertical.

I built a simple elliptic function filter with a null at 790kHz and high pass-band ripple. This
provides better than a 60db null across the modulated bandwidth of the BC station and
negligible attenuation on 160m - but very variable attenuation across the remainder of 

the broadcast band. The filter has only 3 capacitors and one inductor.

I think this is a better approach than just a series tuned circuit as all parameters
(including the necessary filter complexity) are under the designer's control.

Now the other BC station has closed down and I have no AM stations within 150km -
by far the best solution!


73 Roger
VE3ZI