FM Trap For Airband

[skatertj]

Quick question, are you guys hooking your filters directly to the scanners bnc out or are you running some coax between them? I need a fm trap for my pro-2055 but i dont know if i want to find a foot cable or just hooking it directly to the scanner. The scanner will be placed in my car so idk if there will be any strain the the scanners bnc connector.

 

[SCPD]

Mine is setup like this. Disscone antenna going into a splitter (1 to 3) and then from the splitter to the fm trap (with coax) and from the fm trap to scanner (with coax). I would make or buy a small 1ft piece of coax to go from the scanner to the trap.

 

[ridgescan]

I know this is an old thread but i also just got the FM trap from radio shack and put it on my 996t and WOW big difference, Thanks ridge.

Mike

I know right? I was really impressed with the improvement too! And now I continue to enjoy awesome airband stuff I never had.

 

[ridgescan]

Maybe its just me but it seems the trap opened up most of the public safety band 400-480 as well as the airband.

here I get the same signal level at 488megs but improved voice with this trap. I can finally copy South San Francisco police on 488.4625 at 2 bars. I was totally deaf to that agency, even though at only 8 miles, because its repeater antenna is totally blocked by San Bruno Mountain.

 

[ridgescan]

Quick question, are you guys hooking your filters directly to the scanners bnc out or are you running some coax between them? I need a fm trap for my pro-2055 but i dont know if i want to find a foot cable or just hooking it directly to the scanner. The scanner will be placed in my car so idk if there will be any strain the the scanners bnc connector.

This is mine-I fabbed a relief support that rests on the table keeping the stress off the connectors

 

[737mech]

NmelfI Check PM's

Ck pm's ok?

 

[vagrant]

Just to add...

I purchased a couple FM Traps from RadioShack a few months back, but didn't really notice a difference with the one I put on the scanner feed. Well, for whatever reason today, my brain decided to mess around with the various cable feeds and sure enough, the filter was patched into a dead line not even attached to an antenna, nor a radio. - sigh - (The scanner was hooked up to the discone though. I'm not that crusty.)

Anyways, I put it inline with a patch cable, as well as a lightning arrestor, to a Pro164 and holy cow wow! What a difference. The noise floor dropped and I can hear all kinds of feeds now. I must have some heavy FM noise in my area. I'm now clearly pulling in Point Mugu, Lemoore NAS, and Edwards AFB according to the RR database. I'm also pulling in something on 327.0, but I'm not sure who/which it is. I'm even pulling in the NOAA feed from Bakersfield, which I couldn't get with just the discone, as well as a state park ranger freq that's only 10 miles away.

I'll be picking up two more traps for additional radios tomorrow. I'm expecting to hear all kinds of traffic during business hours. For $7 it is well worth testing your setup with one inline.

 

[ridgescan]

Just to add...

I purchased a couple FM Traps from RadioShack a few months back, but didn't really notice a difference with the one I put on the scanner feed. Well, for whatever reason today, my brain decided to mess around with the various cable feeds and sure enough, the filter was patched into a dead line not even attached to an antenna, nor a radio. - sigh - (The scanner was hooked up to the discone though. I'm not that crusty.)

Anyways, I put it inline with a patch cable, as well as a lightning arrestor, to a Pro164 and holy cow wow! What a difference. The noise floor dropped and I can hear all kinds of feeds now. I must have some heavy FM noise in my area. I'm now clearly pulling in Point Mugu, Lemoore NAS, and Edwards AFB according to the RR database. I'm also pulling in something on 327.0, but I'm not sure who/which it is. I'm even pulling in the NOAA feed from Bakersfield, which I couldn't get with just the discone, as well as a state park ranger freq that's only 10 miles away.

I'll be picking up two more traps for additional radios tomorrow. I'm expecting to hear all kinds of traffic during business hours. For $7 it is well worth testing your setup with one inline.

That little trap makes you realize how well your scanner and discone can actually perform!

 

[vagrant]

Oh wow, I'm getting all kinds of stuff now that I haven't received before. What a difference. I further read about a combined notch filter which may help even more, as I have some dastardly AM BCB traffic. I've got a PAR high pass filter arriving Thursday to help the SW receiver with that problem.

As I'm listening in this morning, I'm hearing more and more I've not heard before. My discone is 35' in the air and it's now receiving like I thought and hoped it would, even the Coast Guard up in San Francisco. Incredible difference.

 

[nanZor]

I'll be picking up two more traps for additional radios tomorrow. I'm expecting to hear all kinds of traffic during business hours. For $7 it is well worth testing your setup with one inline.

I'm glad that worked for you! - the RS trap works for many. But for others, if it doesn't seem to work at first, don't give up! The rs trap has the notch high in the band, and didn't touch my fire-breather down on 88.5 mhz - it was only attenuated by the insertion loss alone since the high-frequency notch didn't touch it. And placing two of them inline only results in about 6db more attenuation, not the sum total of each notch-depth.

So while I'm happy that it works for a lot of people, this is just a reminder not to give up at first if the rs trap doesn't seem to make a difference. It is definitely worth a shot at first though!

And if things are bad enough, an fm notch might be a good idea for mobile use too...

 

[Tryton]

Sorry to rekindle this thread, I just picked up the RS FM Trap, It has a in and out. Am I assuming correctly that the feed from the Antenna goes to IN and from the trap to the scanner OUT.. is that right?

 

[aps_ak]

Sorry to rekindle this thread, I just picked up the RS FM Trap, It has a in and out. Am I assuming correctly that the feed from the Antenna goes to IN and from the trap to the scanner OUT.. is that right?

Yes, that is correct.

 

[reconrider8]

Noobish question but how does an fm trap help out on air. i understand it cuts the fm band out but does that allow you to run your scanner at a lower squelsh lvl to pick up more or what?

 

[ridgescan]

It basically keeps the 'bleedover' of powerful BC stations in the 88-108mHz band from supressing signals in the air band just above that at 108-136mHz. Stop in a Shack, buy one for $8 and see. You will be amazed Like the other folks have suggested in here, I am going to upgrade from this one soon as I get the chance. This little gem is impressive-apparently there are ones that do even more. I am all for more

 

[reconrider8]

i went and picked one up and it kinda clears it up some but i honestly cant tell a whole lotta difference and just playing with it i ran it on the fm broadcast just to test it and it didnt stop a whole lot of the signals lol

 

[ridgescan]

i went and picked one up and it kinda clears it up some but i honestly cant tell a whole lotta difference and just playing with it i ran it on the fm broadcast just to test it and it didnt stop a whole lot of the signals lol

Sorry to hear that. You may have a strong FM BCer that is still getting by it. I have Sutro Tower here beaming a few FM BCs from only 1.7 miles away and the trap is very effective here.

 

[KevinC]

i went and picked one up and it kinda clears it up some but i honestly cant tell a whole lotta difference and just playing with it i ran it on the fm broadcast just to test it and it didnt stop a whole lot of the signals lol

The idea isn't to "stop" the signals, but to reduce them enough so they stop overloading your scanner. Maybe you are being affecting by FM broadcast desense so that's why you don't see much of a difference.

 

[reconrider8]

How do you stop that and also i dont have an external antenna but i have sputnik mounted inside the house

 

[Tryton]

a Notch filter will completely remove it. google for fm notch filter

 

[reconrider8]

i think one problem i have is just normal interference. like i added the fm filter and the 118-120 was terrible but not really sure why unless its because the antenna is close to the computer (maybe 12' away)