Maxtrac GM300 High Power TX

[twowaytekk]

I have some Maxtrac, Radius M120, and GM300 radios that are transmitting higher power than they should. Some of the 45 Watt radios are well over 100 watts. I'm aware how the PA works, and the PA mod. However this issue occurs on some channels and not others. All the programmed Channels are within the band limits of the radio. Also when I program the radio with a new freq on the channel that was transmitting fine, the new channel transmitted too much power. I program the old codeplug and all is fine. I haven't made any other changes in the codeplug. Any ideas why the radio is transmitting too much power on some frequencies and not others?

Mark

[Jim202]

I have some Maxtrac, Radius M120, and GM300 radios that are transmitting higher power than they should. Some of the 45 Watt radios are well over 100 watts. I'm aware how the PA works, and the PA mod. However this issue occurs on some channels and not others. All the programmed Channels are within the band limits of the radio. Also when I program the radio with a new freq on the channel that was transmitting fine, the new channel transmitted too much power. I program the old codeplug and all is fine. I haven't made any other changes in the codeplug. Any ideas why the radio is transmitting too much power on some frequencies and not others?

Mark

My first thought would be to do a RF power output alignment on the radio. If after that, it still does it, my guess would be someone hacked the radio. The next step might be to locate a good codeplug with the same model number and clone that into the radio. After the clone I would suggest that you do a full alignment on the radio.

Jim

[jackhackett]

What are the band limits of the radio?
What frequency is causing high output power?
How are you measuring power out?

[twowaytekk]

I have multiple radios doing this. All came from the same source, but most have been problem free. Most are 146-174. 154.600 has been a proble., along with freqs in 159 range. Power is.being measured with a Bird watt meter.

I will try a known good codeplug and see if that cures it. I have done an rf alignment on one if them and still had issues.

[jackhackett]

Having the same problem with multiple models of radios, and having them put out far more power than they should be able to makes me think the problem is in the measurement.

Ideally, they should be checked on a service monitor. If one is not available they should be checked using a dummy load connected right after the meter, NOT into an antenna.

I have often seen watt meters give extremely high power readings when operating into a bad antenna, the radios aren't really generating higher power than normal, the meter is giving a false reading due to an impedance mismatch. The reason it happens on certain frequencies and not others could be due to where the standing waves peak on the feed line.