Repeater makes a loud squeal

[WQTK732]

Ok so I'm really new to the repeater world and I have mine setup on 462.675 pl141.3 and the last two days after you release the ptt button there is a loud squeal during the short tail. It's not every time but most. It's only done it since it's gotten real cold outside. The rptr it's self is indoors so that's warm. I had a audio file but I can't upload it..

 

Any ideas?

 

Bill

Wqtk732

[PastorGary]

Bill, that happens a lot in cold northern states weather. There are a number of causes, but one common cause is a higher than normal system SWR which introduces some harmonic radiation back into the duplexer as the noise that you are hearing.  This MAY or MAY NOT be what your issue is, but since you are in New York State, the weather lately has been affecting many systems with ice.  Others may have opinions here as well, but see what happens after things 'thaw out' a little.

[WQTK732]

Yea I left it for a month and it still does it once in awhile. .

 

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[Shriekmau]

I have heard of duplexers being thrown out of tune due to extreme heat or cold. If you have a way of checking them, start there. Sometimes when they are thrown out of tune it doesn't recover on it's own and must be re-tuned.

[Guest spd641]

Possibly hetrodyning with another repeater on the same frequecny would be a guess...William

[PastorGary]

William - that's a thought... on Wednesday, I was traveling well south of my normal location and wanted to speak with Jake (WQTAXXX) - When I called him on our local system, I also activated the only other repeater in my State set up the same way as our local - from 115 miles away... and I heard BOTH repeaters on at the same time.  The repeater time-out is different on both, so I knew that it was the other system well to my south that also came on. When two FM transmitters come on at the same time on the same frequency and at a nearly identical signal strength, 'growling' that is heard is the two systems competing to get into the mobile receiver.

 

If Bill can do a system search in his area for another system with the same access tone or code being activated from a mobile, that might shed some light on the 'noise'.

[WQTK732]

I have checked that and it's definitely not another rptr cause the nearest one from set up the same is about 285 miles away and I really doubt I can activate that one with my ht lol.

 

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[Guest spd641]

There is again the possiblity there may be another GMRS repeater in your area that you may not be aware of.There is no way of knowing who owns a repeater.The listings here at www.mygmrs.com are on a voulntary basis and members who join the site have no obligation to list their repeater.You will always have GMRS repeater owners who choose not to list their repeater and their repeater may be for their personal family use only or they wish to keep private.There is no offical site for listing GMRS repeaters since it is no longer a FCC requirement...William

[PastorGary]

Just in case it IS a technical or configuration issue with the system itself, perhaps we can all discuss internal repeater possibilities. I know that a high SWR can create stronger than normal primary to secondary harmonics and sub harmonics.  I remember a situation in Tennessee about 20 years ago where a law enforcement repeater antenna had some storm damage and with the high SWR, the transmitted signal was creating a harmonic into the duplexer that caused an audio feed back between the repeater receiver and transmitter whenever it was lit up by a mobile.  Perhaps that might be close to what is happening here....

 

However, it could be a sub harmonic that is just causing a squeel or high pitched growl, rather than actual audio feedback from interaction between the transmit and receive sections.   ?????????????

[JohnE]

moisture in the cable will also create "noises" but will not show up on an SWR meter. I have seen it many times it doesn't take much. blocked condensation hole on an antenna will do it in very short order and "if" that migrates into the cable your only option is to replace them both. been there done that.

if the receiver is tuned up wrong it will also create these noises. RSSI too low/squelch settings too low will have the same affect. have this w/Kenwood all the time.

I have seen duplexers go bad and do this but that is pretty rare, unless it is poorly tuned.

now if the transmitter is putting out junk this will wreak all sorts of havoc in you system and others miles away. rule of thumb is "if it doesn't sound right it probably isn't".

as an example my 650 had a moisture problem last spring. it didn't sound right to me for a week or so, checked it w/Bird 43 wattmeter all looked fine. another week later it go worse. this time after putting the meter on it I went topside and opened everything up to inspect it. moisture in the connector and the cable. cut 6' off the cable to see if it was clean, it was. put new connector on it and changed the antenna. upon further inspection the fiberglass had become porous and that is how it got wet inside the cable, it migrated down internally. go figure.