MTR-2000 UHF Repeater - "Double Beep"

[railtrailbiker]

A 100w UHF MTR-2000 repeater was recently installed at our site. The owner cut the power output back to 60w by request of the site manager. The repeater is now transmitting "double beeps" over the air. These beeps were not present when the repeater was operating at full power output when installed at its previous site. VSWR was checked with a Bird watt meter upon installation and showed as being completely flat. Output power was also checked with the Bird and verified at 60w. Other than the beeping, the unit is performing flawlessly and providing transmit and receive coverage identical to or better than other repeaters at the same site. The owner has not been able to reach the site to check the unit with a laptop. We've heard that the beeping could be a warning that the PA isn't operating at full power output, or related to AC power fluctuations at the site. Your thoughts?

 

[mmckenna]

If I recall correctly, that means it thinks the PA has failed.

 

[kf8yk]

2 beeps is PA fail, but this is somewhat generic. You need to look at the alarm log with the programming software to see the specific condition that is raising the PA fail warning tones.

I have a VHF MTR that occasionally throws PA fail tones when the antenna gets coated in ice. SWR is still below 2:1 when iced over but it still trips the reflected power level in the MTR. Once the ice melts everything returns to normal.

 

[wa8pyr]

If I recall correctly, that means it thinks the PA has failed.

Many of their repeaters (probably all) actually have an alarm set point for TX power which is part of the alignment process; if the TX output power drops below that point the repeater will start sending an alarm.

When doing the alignment, if you cut the power back you also have to reset that set point; don't do it and the alarm circuitry will think PA failure, as @mmckenna mentioned.

OR.... does the repeater think the AC power has gone (even if it hasn't)? Not sure about the MTR, but when running on battery the MSF5000 would cut back the TX power and make the double beep sound so that the users knew you were running on battery backup.

 

[jeepsandradios]

And being you said repeater check with a watt meter before the duplexer to make sure nothing is wrong with it. I have seen folks swap TX/RX lines and the PA will shut down as it should.

 

[MTS2000des]

Connect your programming setup and read the logs: it could be a high VSWR, power supply voltage, VCO coming out of lock, the logs stored in the station will tell you what exactly is causing the over the air alarm. All the other advice is solid, but always check your logs!

 

[RodStrong]

The manual does suggest it's a PA issue. One of our VHF analog MTR's here started having the beeps consistently several years ago, and it still works fine to this day (the machine is used moderately on weekdays). I've been wondering if it's every going to fail, and it keeps chugging along.