Yaesu: Yaesu FTM-3100R and NMO Receive Issues

[J_edgerton]

Hi folks,
I am having an issue with a Yaesu FTM-3100R. The set up is the rig with power and ground through the firewall and straight to the battery. The antenna set up is a NMO with a Tram 1121 quarter wave antenna. My issue is when I plug the antenna into the so-239 on the back of the radio, I receive 4/5 bars RSSI from the local NOAA weather station at FIRST contact with the center conductor but when I thread the sleeve all the way snug onto the connector the signal drops out to near nothing. Even on open squelch there is nothing. When I unthread the connector the signal comes back loud and clear just before I pull the connector out.

This issue has me utterly befuddled and that’s why I figured I’d reach out to the experts. Fire away! Help!

 

[mmckenna]

Sounds like a short circuit in the coax.

Remove the antenna and unplug the coax from the radio. Check for continuity between the center conductor and the outer shield. It should show open.

If that isn't it, let us know and we can try some other troubleshooting steps.

 

[trentbob]

I agree. That's a classic short circuit issue. How old is the coax, you have a drilled hole for the NMO mount? lip mount? Some where the coax is being damaged/ compromised or you have water damage or the disc is improperly mounted... I am not a big fan of tram mounts. The so 239 on the radio could be damaged also. Look for any cracks or broken pieces.