Batboard

Just got a GR-1225 for a repeater and it seems when transmit is on (including when it id's) it gives a squeal type sound like feedback. I tried adjusting stuff in the program including in the service part but nothing changed so I put everything back to the previous settings. Its almost like when you are too close to a radio when the volume is up too far. but it does it on the repeater transmit when your not talking on it but when the repeater is keyed like when it is iding. Would I have to adjust the audio inside the radio? or am I missing something?

Thanks!

John KB3AWQ

sounds like RF is getting back into the recieve side...check your duplexer..

CircleBaty

OK Thanks I can see if I can get them checked again, they were tuned a week ago. It sorta seems like the audio level or either the transmit or receive side is a hair to high as it repeats fine. Havent seen much on audio adjustments

Is this a new problem? Was this the reason for the alignment, or did the trouble start after the alignment? Is it possible the repeater bandwidth setting was changed from narrow to wide band?

Not sure I just got it off ebay a couple weeks ago and programmed it and had the cans tuned to what I was going to be using it on and plugged it in. I put all the setting back to where they were since they didnt seem to take care of it (in the program) Not sure on the background as the person I bought it from was not either he said he got it with a lot of other things. It repeats fine and doesnt seem to be desensing at all it just sounds like there is some sort of whistle type tone when it is transmitting which probably could be overlooked as it doesnt cover the audio up but it is there. I know in the settings it has the 12.5 or 20, 25 check option which I left it on the 20 option but I did try it on 12.5 as I was thinking the same thing. I even tried that with xpand and no change.

I switched the cans to the GR300 I also have and all was well with that so I dont think it is a duplexer issue. Its not on the receive it only comes in when transmitting. I wasnt sure if there was an adjustment in the radio itself (although I wouldnt see why someone would have went thru the trouble of taking it out of the case and mess with something in the radio but I guess is possible). Its not even really a squeal it sorta sounds like someone continuously whistling with no teeth or thru lips or like blowing on the top of a beer bottle (not real loud just lightly)

I just found this article http://htmcnetworkcitizensband.wordpres ... -transmit/

I hooked a mic up and unhooked with no diff
I turned the repeater gain, mic gain, and another other gain down and made no diff. in the software.

Edit: I should add that its not heard or at least not noticeable while talking on the repeater or on the mic for the repeater. The only time I have heard it is while it cw id's and when you release the radio PTT I can hear it on the hangtime part

Something I havent tried is grounding which is possible, I will try this when I can and repost the results.

1) rf Getting back into the receiver side through the duplexer

2) One of the pin diodes is shot

3)RF leaking from the bad solder joints of the PA transistor due to excessive heat causing a bad solder joint

whatever it is, you have RF getting back into the radio...

CircleBat

Do GR rptrs have ID built in? I don't recall. I'm pretty sure they don't. If the only time you hear this squeal is during hang time and ID, is it possible it's introduced by your ID'er?

CircleBat wrote:1) rf Getting back into the receiver side through the duplexer

2) One of the pin diodes is shot

3)RF leaking from the bad solder joints of the PA transistor due to excessive heat causing a bad solder joint

whatever it is, you have RF getting back into the radio...

CircleBat

CircleBat, why are you convinced that it's RF getting back into the receiver or transmitter? Have you witnessed this same issue being caused by RF "feedback"? Just curious... you seem quite adamant about your diagnosis!

As far as for your problem, OP, can you make a recording of it and post it someplace for us to hear?

I can try to record it, was thinking about doing this but wasnt sure what the quality would be.

As for the id being built in, it shows in the software when I read the radio I believe its on the radiowide tab and then there is another tab on the right you click that says cw id so Im guessing it is built in (didnt see anything hooked from the outside the radio either)

I was thinking about just taking it over to our local dealer and have him take a listen to it (I know him pretty well so its not like a regular dealer)

After 20 years in radio and never heard of such a thing. Im pretty positive its not the duplexers at least. I have another UHF repeater that I had them hooked to and it worked perfect so definitely is something having to do with the GR1225. Im not really a radio surgeon unless I am familiar with the problem so if it is any of the things listed above it will have to go to the dealer anyway. If it was just the matter of the audio being adjusted I could take care of that but apparently the adjustments in the software dont do much so unless there is something that would be adjusted inside the radio (which would be nice cause I would turn down the cw id a little anyway as in the software you can change it from 750 hz to 1500hz but is still just as crappy in my opinion). I will try to do some more tests with it and try to record it as soon as I can.

kb3awq wrote: Its not even really a squeal it sorta sounds like someone continuously whistling with no teeth or thru lips or like blowing on the top of a beer bottle (not real loud just lightly)

I have heard a similar sound with bad cans/duplexer. However, trying your duplexer with another repeater seemingly eliminates that.

The other thing this sounds like is microphonics...the Maxtrac/GM300 were quite famous for this when their board interconnect pins became oxidized/dirty. I would try stripping the repeater down, removing the RF & control boards & cleaning any pins & even the ground connections around the screw holes where the boards make contact with the metal chassis.

Bill_G wrote:Do GR rptrs have ID built in? I don't recall.

They do, plus a little "beep" courtesy tone and all the interface options a boy could dream of.

OP, I'd start by pulling the R1225 RF drawer out of the cabinet and keying it into a dummy load or service monitor WITHOUT the duplexer while powered by a known clean 12V power supply. Basically you need to remove as many possible points of failure as you can until the problem goes away, then reintroduce them one by one until it comes back. If the drawer by itself still "squeals" even out of the cabinet and only keying into a dummy load with a palm mic (plug a GM300 head into the front to power it up with and give you a mic jack) then open it up, pull the RF and command boards out, and inspect the passthrough pins for weak solder, dirt, corrosion, etc.. they've been known to cause audio issues, and sometimes a simple unplug-and-reseat will fix it (been there done that!)

try lowering the power on the repeater and see what it does.. these aer good repeaters but lotsa surprises in them.. also try the repeater without the microphone.. I have a hunch it may be a shot rf switching diode as i've seen i've already it in one of our repeaters

I was able to upload the recording I made with my phone. It almost sounds like the fan on the power supply. Here is where it can be heard but you may not be able to listen to it on any media player but it plays on my Droid Razr and Real Player on my computer but Windows media player wouldnt play it. http://www.mediafire.com/?ho4vjmavt5r9re3 http://www.mediafire.com/?ho4vjmavt5r9re3 is where the audio can be heard and toward the end it has me giving my callsign to just add audio to the mix. It doesnt seem real bad but I am used to hearing nothing in the background. Also note there is a 173.8 PL tone so you may here this also. All the responses are appreciated and I will check into what has been said so far.

I have the repeater on low power but I guess it could be adjusted more by messing with the settings. I have tried with and without the mic plugged in to the repeater and was the same. There is a fan attached to the outer case in the back which is currently unplugged so the only fan is in the power supply.

The fan should have a DC filter in line with the power supply. Some DC fans make noise in the supply which gets back into the radio's D C power.

If it is a stock power supply it should have a separate filtered output for the fan.

try using an external power supply

OK. It appears as if it is the fan in the power supply what I was hearing. The power supply (guessing the original) has a switch on back to run the fan all the time or temp. control. I switched it to temp control to see and everything sounded good.