Antenna Interference...

[btritch]

I have a rather weird question, Well I have never experienced anything like it, someone else on here might have so I'm going to see what I get as responses, Here goes,

I have an ST 2 scantenna on a tower about 50 or so feet in the air, I originally used RG 58 that came with it, BUT Soon learned that LMR 400 was better if not the best, SO, I changed over to it and left the antenna at that height...before I changed I never noticed it but since I've changed I have noticed something weird.. When any of the 800 or UHF channels TX it's usually fine...However on the VHF band, Not on all of them, just some of them, mainly the 155 and 158 areas and sometimes the 156 area. I notice that when a department keys up and starts talking that they are quite fuzzy and hard to hear (note: They are quite aways away, They're local but not in town, About *(If I'd have to guess)* 30 to 40 miles roughly...When they just start to key up and during the entire conversation they are hard to hear and fuzzy which I can understand being at that distance, however, toward the end of the conversation no matter if it's dispatch or car right about 10 seconds or so before the end of the conversation it will get clear as a bell just as they would if they were local...Why would they start out fuzzy and end up clear, I can maybe see interference once in awhile but it does this every single time just about...Does anyone have any idea why?

 

[k9rzz]

Too much signal that is overloading your receiver? Dunno what radio you have, but if it has an attenuator - try put that on. Might help.

 

[btritch]

Overloading it from 40 miles away? Is that possible? I'd not thought that..But i'll try it as soon as it stops on it again and see! oh, and I've got a pro 97 and also a RS 2025, they both do it but the 2025 doesn't have ATT choice on it..

 

[fineshot1]

It sounds to me like you might have some freqs programed that may be slightly off frequency.

Have you confirmed that these freqs you have in your scanner(the ones you are rx'ing fuzzy) are programed correctly to the exact frequency? Many of the older model scanners can not do the new vhf-hi band splinter channels(which are now on 7.5khz boundaries). So for example the older band plan had(and still does) a channel at 155.160 with a channel at plus and minus 15khz but now its plus and minus 7.5khz so the older scanners will not be able to be programed with the new splinter channels because the firmware in the older scanners will round out the freqs to the older 15khz boundary. This newer band plan has 7.5khz channels in certain segments of the vhf-hi band.

NOTE: If they are programed correctly then you could be hearing some slightly off freq chatter from one of those splinter channels that may be adjacent to what you have programed.

 

[chrismol1]

It sounds to me like you might have some freqs programed that may be slightly off frequency.

Have you confirmed that these freqs you have in your scanner(the ones you are rx'ing fuzzy) are programed correctly to the exact frequency? Many of the older model scanners can not do the new vhf-hi band splinter channels(which are now on 7.5khz boundaries). So for example the older band plan had(and still does) a channel at 155.160 with a channel at plus and minus 15khz but now its plus and minus 7.5khz so the older scanners will not be able to be programed with the new splinter channels because the firmware in the older scanners will round out the freqs to the older 15khz boundary. This newer band plan has 7.5khz channels in certain segments of the vhf-hi band.

NOTE: If they are programed correctly then you could be hearing some slightly off freq chatter from one of those splinter channels that may be adjacent to what you have programed.

happens to me on my handhelds. when the scanning stops at a certain freq say 154.90 its fuzzy, but at 154.950 or even 155.00 thats the freq that they are using

 

[fineshot1]

happens to me on my handhelds. when the scanning stops at a certain freq say 154.90 its fuzzy, but at 154.950 or even 155.00 thats the freq that they are using

There is no 154.9000 channel, there is a 154.8975 or 154.9050 channel.

There is a 154.9500 channel.

There is no 155.0000 channel, there is a 154.9950 or a 155.0025 channel.

As I stated before it seems you have the channels slightly off frequency and
thats why they sound fuzzy. Thats audio distortion from being off frequency.

 

[btritch]

That could be, strangest thing, on my olderst scanner it doesn't do that, On my new pro 97 it does. I'm using the frequencies listed for Poinsett County AR on the database...Harriburg site, 155.190

 

[DPD1]

Everybody has their own idea of what fuzzy sounds like. Maybe you can post a sound file somewhere. There's different kinds of 'fuzzy'.

Dave
www.DPDProductions.com
Antennas & Accessories for the RF Professional & Radio Hobbyist

 

[ridgescan]

Plus you said it only happened AFTER you changed coax?? So how can it be off freq if it didn't do it with the old coax?

 

[fineshot1]

Plus you said it only happened AFTER you changed coax?? So how can it be off freq if it didn't do it with the old coax?

He said he changed from RG58 to LMR400. So my theory is he is hearing weak signal from adjacent splinter channel allocations he has never heard before. Just a theory....

 

[btritch]

He said he changed from RG58 to LMR400. So my theory is he is hearing weak signal from adjacent splinter channel allocations he has never heard before. Just a theory....

My guess is either that or another agency even farther out than that...What are some sites to post sound files to and I'll try to get one..