Filtering

[w4rez]

My location, like many others, is plagued by interference from a nearby VHF commercial paging transmitter. The problem seems to be as much of a problem with the poorly designed receivers in most scanners, as I can tune some of the interfered-with frequencies on my Icom 2 meter rig and not have interference problems.

I am thinking that a good (although a bit expensive) solution would be to buy a set of secondhand VHF duplexers and tune the band reject side to the frequency of the offending transmitter and leave the bandpass side unused. Has anybody done this and if so, what were your results? I'm just wondering if my problems are more intermod problems than with the scanner's frontend being overloaded by the signal on the fundamental freq.

 

[kingpin]

Par electronics makes notch filters you can get that will filter 152, 158, 1nd 162 MHz frequencies. They run around $60 and up but I've read nothing but great reviews.

 

[fineshot1]

Par electronics makes notch filters you can get that will filter 152, 158, 1nd 162 MHz frequencies. They run around $60 and up but I've read nothing but great reviews.

kingpin - you beat me to it. I was going to recomend the same solution. I have used these mostly in the car and they work great.
w4rez - this is what you want. the duplexer idea is likely to be alot more expensive and wastefull...

 

[rescuecomm]

The PAR units are helical or high Q strip designs. You won't need a tuned cavity filter unless there is a frequency close to the 152mhz that you wish to monitor. A single notch cavity will remove the offending signal by as much as 30-40 db. I saw one at the Shelby NC hamfest, but don't remember if it was a notch or a pass-band.

Good luck,
Bob