TopBand: .

[J & AJ Robertson]

Re 160m BC QRM.   Two miles across salt water from my QTH I have to put up
with 1 100 KW  (  730 ft mast )   4-@ 20 KW and 2 @ 5 kw between 570 and
1580 khz .  Any receiver with a resonant 160 antenna just blocks up, leds
in SWR glow brightly as do fluo lamps tied to fence lines.      An
excellent article on HIGH pass filters by John W1ETC QST October 1983 put
me right on track for better reception.                                   
I now have a Butterworth 10th order filter in line permanently so if  you
use Co-ax feed it  can be easily built to take high power Tx or switched 
for receive only.   This type of filter will not cure some problems like
direct pick up of 2nd and 3rd harmonics but it sure is worth playing with
to tune out offending station  mixes.   I get 70 db rejection below 1750khz
 when the inductance slugs are tuned  to the station frequencies.          
                                          73 all Jim ZL2JR.                
                                                                           
                                                                           
                

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