Repeater cuts out and back in

Larry · Post by **Larry** » Fri Oct 29, 2004 4:32 am

I've got a GR1225 UHF repeater that seems to work perfectly with one exception, if a portable radio is transmitting it will cut-out for about 1 second during the middle of the transmission then cut back in. This usually causes the RX'ing radio to miss one or two syllables. It was working flawlessly before I made a slight adjustment to the TX deviation and the TX audio. I set both settings back to the original position but the cut out problem still exists. I made the adjustment because the TX audio seemed quiet or as if the person talking on their radio was far away (which was not the case). Any ideas what could be causing the repeater to all of a sudden do this cut out problem?

Dan562 · Post by **Dan562** » Mon Nov 01, 2004 11:33 am

Not knowing anything aboiut the GR1225 Repeater or what Portables you're using in the system makes it difficult to consult on the problem. Generally knowing /\/\ Infrastructure Base Stations, you must READ the station parameters first before Adjusting or Aligning any settings in the software and then WRITE the new information back into the station. Nothing is done in real time.

Reading the original problem of low Deviation would lead me to believe either the Base / Repeater or the Handheld Portables were configured incorrectly. If the GR1225 station is capable of Wide or Narrow Channel Spacing and the Portables are also capable of the same configuration, then the Repeater could have been programmed for 25 KHz RF Channel Spacing and the Handheld Portables might have been incorrectly programmed for 12.5 KHz RF Channel Spacing making them sound like Low Repeated Deviation.

Go back and recheck the portables and the repeater programming parameters. It is also wise to not ASSUME that the factory has set the Deviation levels correctly before they shipped the product. They hire a lot contract personnel to test the equipment before being shipped out the door, that may or may not even understand two-way radio electrical specifications.

Dan

Post by **/\/\y 2 cents** » Mon Nov 01, 2004 11:49 am

Sounds like a deviation issue to me...

Tom in D.C. · Post by **Tom in D.C.** » Mon Nov 01, 2004 3:03 pm

Is it possible that that the Receive radio is reverting to a Priority listening channel, say channel 1, when you want it to be listening to channel 4 and repeating channel 4 into the transmit radio?

I don't know if that's possible with your setup but it sounds to me as if that's what is happening.

odat · Post by **odat** » Mon Dec 06, 2004 1:14 pm

Duplexer desense?? Altho you didn't make any adjustments there, that's what it sounds like. Strong signals are fine, but weaker ones cut in and out??? Yup!

RKG · Post by **RKG** » Mon Dec 06, 2004 2:15 pm

My first guess would have been roll-off. If an input unit is at the limit of its input range or is sending tone at the lower limit of acceptable (on the order of 350-400 Hz), its is possible for the deviation that results from the input user's voice to momentarily mask the tone. If the repeater is programmed to drop the audio gate the instant it detects loss of tone, this will cause the symptoms you have reported.

Two cures: re-align the offending input units for a higher level of tone deviation, or invoke a setting in your repeater controller called something like "tone hold". This will delay the shutting of the audio gate for X period of time following loss of tone (and assuming no turn off code), so long as freq remains valid.

bernie · Post by **bernie** » Sat Feb 19, 2005 10:10 am

My two bits worth:
I can only guess.
We don't really know for sure that this repeater is operating perfectly unless measurements are made such as Tx power, deviation, Receiver sensitivity, repeat level as well as receiver desensitation,
forward and reflected power to the antenna.

We will say that you have no complaint except for the drop out issue.
I don't think that it is a deviation issue because there would always be distortion, it really takes very excessive over deviation to cause squelch blocking.

Desense can cause "water pumping".
That is that the repeater keys, then un keys when the transmitter causes the receiver to squelch due to desense.
It sounds like an old fashoned farm water pump.
I note that about 13 DB desense on a Micor causes this.

My guess:
Burnt solder on the PA transistor collector connection.
Be sure to use "silver bearing solder" when repairing.