PRO197 FIX For intermod

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SCPD

QRT
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Ok yesterday I got annoyed at my 197 and decided to fix it,it was getting noise in with my local police department.So I get an FM trap from radio shack cut out the coils and used a 100 ohm variable potentiometer shorted the two legs on the one side connected them to the input part of the fm trap and took the other leg and put it to the output of the trap box.I put it on a blank channel,backed the pot off til I got 1 signal bar flickering,ya know what?This scanner is so clear now its amazing!
PS leaave the two small caps on the input and output they go from ground to the center of the f connectors.Works like a charm!
 
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SCPD

QRT
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Feb 24, 2001
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Virginia
no fool

This is one pic with and one without PARKED on 155.910 with NO CARRIER and antenna connected
as you can see the thing works! four bars of NOISE to ZERO bars of noise and yes it receives like a champ!
 

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SCPD

QRT
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Feb 24, 2001
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Virginia
stock

the stock fm trap did jack squat for this scanner gets overloaded by noise when its near say a big city like newark or nyc,i got paging noise from 152MHZ,that is all gone now.
 

737mech

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Clark County, NV.
FM Trap

In the interest of sharing info, I am like you wanting to hear more and clearly, I also discovered that a FM trap helps the scanner. Now let's look at the technical details. What you built, can you put it on an analyzer? The graphs provided by some of the filter manufacturers shows you visually what happens to the signal pre and post filter. I'm guessing you notched your signal enough to dampen the effect of nearby FM radio and suddenly the scanner gives you what you want. Well that's great and all but what if the notch has a resonant repeat? Now you actually lose things in the 800's. Or you could lose in other ranges you scan. This is where a quality filter will really make you happy. You have already identified you have some sort of intermod and the 197 is deaf because of it. I am trying to save you the time, effort and money by sharing my exact same experience. I eventually arrived at this PAR Electronics | Filters for the commercial 2 way market, MATV, FM broadcast, laboratory, marine industry, amateur radio, scanner and short wave listening enthusiasts and bought the scanner fm filter. I am a very happy customer. There's lot's of info here and I have never read a bad review of the PAR products.
As a person with similar interests as you this is my best advise. Of course if you are happy with what you built then great! You fixed the problem!
 

verbatimx

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Dec 3, 2007
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hi K2radio

Can you tell me the capacitors value?

do you have a picture from original fm trap before to be modified?

Thanks
 
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