Batboard

The afflicted radio is an XTS5000 M3 UHFR1 380-470. The radio has functioned properly for about a year. Recently, the user observed low power output on transmit. A quick check with the Bird reveals a spike to ~3 watts (hard to tell, since it's so fast), before folding back to a few dozen milliwatts. It acts like high SWR; however, we've tried two antennas and a dummy load with no change.

The radio has not been reprogrammed nor realigned recently. The problem just appeared.

Thoughts? Bad PA deck? Something else? Any suggestions appreciated.

I had a UHF R1 XTS3k that had this once, and the PA was simply bad. Used regularly, not abused, etc.

I know it's a different radio, but if it helps....



Ray.

This may not apply to your radios problem but it's worth a try.

I remember a service bulletin a few years ago for the UHF XTS5000's where radiated RF was getting back into the radio and falsing the directional coupler/power control loop but as I remember this resulted in distorted audio and I'm not sure if power output was a complaint.

In this case It was caused by a grounding problem with the tabs on the RF board where they fit in to the slots in the metal case.

I can't find the bulletin but I remember the fix was to build up solder on the tabs of the RF board for a tight solid ground connection to the metal case.


You may want to check your radio but as is usual it's probably another issue with yours.

OOPS I didn't read your post entirely and as a result of skimming thru it to fast, I didn't see that it occurs on a dummy load also so I guess it can't be radiated RF so you can disregard this suggested fix.
Sorry

Mike

Ray - yeah, I'm thinking the same thing. Unfortunately a replacement is $355 NSO. I have VHF and 700/800 decks in stock... no UHFR1s. Figures.

Mike - thanks, I'll look for that bulletin. Couldn't hurt to check, and with the other solution being nearly 4 Benjamins plus an alignment, it's a whole lot cheaper!

There is a small blue coax from the ant connection to the board. I have seen this fall apart and show this problem, just open the case and take off the coax and inspect it.