Hot front end

[dick122]

Is there any easy/quick way to tell what is causing the overload on these scanners? I think it might be a local FM station but not sure. I have a scantenna with 75' of lmr-400 coax. Everything on VHF high shows 5 bars. ATT does help for local but kills distance reception. Tried using supplied back of set antenna and it makes a big difference. I can pick up a filter but hate to spend the money on the wrong one. Thanks.

 

[iMONITOR]

This is what you want:

HPN 30118 Combined Notch Filter
http://www.scannermaster.com/HPN_30118_Combined_Notch_Filter_p/24-531024.htm

 

[kinfolk]

I strongly second the suggestion that SIG-INT has given you. Your front end overload is probably caused by a nearby FM broadcast station. The suggested HPN-30118 FM notch filter will do the trick for you. It cleared up my problem and I am DXing VHF-Hi on my GRE PSR400 like crazy. You won't be sorry.

 

[k4njk]

I had a similar problem with my GRE500 when using an external antenna. By using an AOR 8200 wideband receiver I was able to determine the cause of the interference was nearby FM broadcast stations. I purchased a filter from PAR electronics and I cannot believe the difference. I went with the PAR filter because a graph of the filter's response was available on line and I was able to speak directly with the owner of the company. Dale tuned the FM filter maximizing the notch on the 3 FM broadcast frequencies I requested and reducing the attentuation above 118Mhz as to not impact my airband monitoring. Here's the link: http://www.parelectronics.com/fm_broadcast.htm

 

[mtindor]

I had a similar problem with my GRE500 when using an external antenna. By using an AOR 8200 wideband receiver I was able to determine the cause of the interference was nearby FM broadcast stations. I purchased a filter from PAR electronics and I cannot believe the difference. I went with the PAR filter because a graph of the filter's response was available on line and I was able to speak directly with the owner of the company. Dale tuned the FM filter maximizing the notch on the 3 FM broadcast frequencies I requested and reducing the attentuation above 118Mhz as to not impact my airband monitoring. Here's the link: http://www.parelectronics.com/fm_broadcast.htm

You gotta love Dale. He knows the questions to ask and then fine tunes those filters to work great. You'd be hard pressed to break his filters.

I've never tried the notch filter mentioned by earlier posters, but I've seen many good reviews about it on these forums.

Mike

 

[iMONITOR]

Agreed, PAR filters are top notch (no pun intended), but most scanner users don't want to pay any more than they have to.

 

[smokeyjones666]

I got one of those PAR FM notch filters for my PSR-500 and it cured most of my problems. I get terrible intermod from FM radio broadcast from a pair of towers about 5 miles away from me and the FM filter really helps a lot. I also get a little trouble from a powerful weather radio transmitter located near by as well, but that PAR FM notch filter really changed a lot for me.

 

[SOFA_KING]

The scanner master filter looks very good for the price. If you checked the pictures they put up under "Larger Photo", they show the tracking generator sweep. That would do the trick on FM. It is also great for hams who use HF in the same location as the scanner or someone who wants to reject HF interference.

http://www.scannermaster.com/v/vspfiles/photos/24-531024-3.jpg

Since I like to scan down to 29 MHz, I would retune to low filter to a lower frequency. I bet it is not hard to do. I happen to have a good tracking generator (lucky me). When I was fed monitoring in NYC I used amateur radio diplexer filters and custom tuned the band pass on them to eliminate images from comercial freqs. That was the only way to clean up that mess...and it worked great! There are many amateur radio filters out there that can be used to clean up the front end issues on a scanner. Check out the specs and see if the pass bands would do what you want. Sometimes you find the perfect filter at a low price.

Phil

 

[Tom_G]

I remember reading that the scan-tenna was notorious at bringing in the FM broadcast signals also.

 

[dick122]

No Help???

Hi folks,

Well, I purchased the filter that SIG-INT said and it did not make any difference at all! I have a PAR filter for a paging transmitter in the 152 range that works fine. I connected both filters to my coax and scanner and VHF high is still overloaded! I can use ATT but that kills the DX that i want to hear. Local stations are fine with the ATT on. Any other ideas?

 

[smokeyjones666]

I wonder if it could be local television broadcasts for you as well. I know I sometimes hear the audio from tv stations that are broadcast from the same location as my interfering FM stations (I've never written down the frequencies and tried to figure it out, but I'll bet they're probably harmonics of the tv audio frequency.) I suppose another possibility could be a local weather radio transmitter, but that's only from my own personal experience as well.

I just make all this stuff up anyway, perhaps what you really need is a friend with a spectrum analyzer!

 

[iMONITOR]

Hi folks,

Well, I purchased the filter that SIG-INT said and it did not make any difference at all! I have a PAR filter for a paging transmitter in the 152 range that works fine. I connected both filters to my coax and scanner and VHF high is still overloaded! I can use ATT but that kills the DX that i want to hear. Local stations are fine with the ATT on. Any other ideas?

Sorry to hear that didn't do the trick. Everyone else on RR that has purchased one claimed success. At least you can return it for a refund.

How do you know the PAR filter is working for you if you still have overload in the VHF/Hi band?

 

[iMONITOR]

Have you tried using the Spectrum Sweeper feature on your radio to find the offending signal?

 

[dick122]

I tried taking the Par filter off last night and i got the usual bleeps and noise on several freqs. The filter clears it right up. Being new to this type of scanner, how would I use the Spectrum Sweeper to find the interference? I really appreciate all the help and advise!

 

[iMONITOR]

I tried taking the Par filter off last night and i got the usual bleeps and noise on several freqs. The filter clears it right up. Being new to this type of scanner, how would I use the Spectrum Sweeper to find the interference? I really appreciate all the help and advise!

I may have confused everyone. Spectrum Sweeper is a GRE term. Radio Shack calls it Signal Stalker II Object (STLK). It's covered on page 59 of your manual.

Signal Stalker II Object (STLK)​

​

​

A Signal Stalker Object (STLK) stores the parameters
necessary for the radio to rapidly sweep a range
of frequencies for strong signals from nearby
transmitters. A STLK object can be used for
standalone operation—the radio just sweeps and
stops when activity is detected, or for stalking that
is performed while the radio is scanning. During
scanning, the radio will check for activity on all the
enabled Scannable Objects: TGRP objects, CONV
objects, LMIT objects and STLK objects.
Essential Parameters
By default, a newly created STLK object is
ready to go without any changes. In its default
configuration, the STLK object will sweep through
all of the important land mobile radio bands
and look for strong signal activity from nearby
transmitters. You may wish to include or exclude
some bands in your sweeps in order to check other
frequency ranges or to limit the amount of time
the scanner spends sweeping frequency ranges
where local transmitter activity is less likely. See​

“Appendix B: Detailed Menu Reference: STLK Menu”

on

page 122 for detailed menu information.​

​

 

[Sinister]

Have you tried shutting the Att off on the channels you speak of that are not local. And leave Att on the local channels.

 

[dick122]

<Have you tried shutting the Att off on the channels you speak of that are not local.>

Yes I have tried that and I still get 4-5 bars with no noise at all.

 

[SOFA_KING]

I am also getting nailed on the front end with three bars in the house with the telescopic antenna and five bars on the roof discone. I have some ham diplexers and duplexers that I am going to try. I think my Diamond MX2000 triplexer is going to help since the filter has a center band pass of 110 to 170. I can retune the top end to go to 174. The low end will pass low band, and the top end will pass 300 and above. That knocks out all TV and FM.

http://www.rfparts.com/diamond/mx2000.html

 

[DaveNF2G]

I use full time attenuation on all VHF high and milair frequencies. Contrary to what has been reported, it does not knock out distant stations. It lowers the noise floor enough so that the more distant stations can be heard, and clears extraneous noise from local signals.

 

[ratboy]

On my sweeps, I have a couple of FM stations that can be heard, but the killer is the 155.130 PD transmitter across the river from me. It's super strong, full quieting without any antenna on most scanners, and just rips up VHF in general when they key up on my Pro-197. I'm going to call Par and see if there's anything that can be done to notch out 155 about 6 DB and leave the rest of the band intact. Right now, VHF is fine on the factory whip, when the 155.130 dispatcher isn't talking, but when she does, I can't really hear much at all, and the squelch breaks constantly with pulsing hash. I'm tempted to just eliminate all scanning on my Pro-197 below the Mil Air freqs, and get another scanner that isn't so intermod prone on VHF, like an amateur mobile (The one I have, an Icom IC-2100 blows away any scanner I've ever had, RF performance wise), and just live with the slow scan speed.