Repeater Antenna HELP!!!

[WQOC472]

Hello,

I have a problem... I have a Motorola GR1225 UHF Repeater that i use for GMRS communications. I have the repeater connected to a Tram BR-6155 Repeater antenna, between the repeater and antenna i have Andrew LDF4-50A 1/2" Hardline. The antenna is located on top a 30 foot tall building.

On recent evening i was attempting to key up on the repeater (I was about 3 miles away, up until that time i had no issue getting 7+ miles of repeater coverage) I went to the repeater location and tried keying up again and i wasn't able to hit the repeater until i got right under the antenna, even then there was a lot of static. I thought the Power Amp on the repeater went out so i replaced the repeater with a smaller backup repeater, to use until the i could get the GR1225 fixed. When i hooked up the back up repeater i had the same problem, no power output, i was standing about 100 yards from the antenna.

So... i have came to the understanding that the antenna is broken and the repeaters are just fine. What is the best thing to do? Just replace the antenna? I'm almost certain the coax is fine, i just installed it about 2 months ago. I have had the antenna in use since March of this year.

Any help or suggestions would be greatly appreicated!!!

Thanks,

 

[EC-7]

You need to check a few things BEFORE you use the new repeater.
Check the jumpers to the duplexer for shorts or bad / loose connections.
Check the hardline for shorts / loose connections.
A simple multimeter can do this. A SWR meter will help after that.
You can use a simple antenna, even a mobile antenna to test. Try using a separate antenna on the RX and TX side.

If you have a short somewhere in the coax or antenna, you could blow an expensive Transmitter or Amp.

 

[KD8MRC]

You really should use a antenna analyzer to check everything before hooking up any TX to a antenna

 

[prcguy]

With a watt meter and load you can check power at the output of the transmitter, the duplexer and finally at the end of the hardline at the antenna.

With known expected loss for the duplexer and hardline run you can not only isolate the main problem but discover other subtle problems you didn't know existed.
prcguy

 

[WA4VBC]

As already suggested, use a watt meter and a dummy load to check the power output of the repeater and then check it at the last point before the coax to the antenna. If all is well, then use an antenna analyzer to determine if the coax is bad or if the antenna bad. If no analyzer is available, you may have to move the dummy load to the base of the antenna to isolate the problem. I would also use the watt meter and dummy load on the GR1225 to determine if it is OK. KAE5442