At a recent first aid event, the event organizers had provided us with some HTs to use for coordinating medical care as needed. Unfortunately, some of their radio techs hadn’t been able to come to the event, so they were flying a bit blind and were encountering some issues with their setup.

I had my NanoVNA with me as part of my standard comm gear for event coverage, but they were unable to give us information about which frequencies they were using. The radios had come from a rental company pre-programmed. So we used the rtl-sdr and with a little experimentation were able to identify the simplex and repeater frequency configurations for each channel.

Then with a little NanoVNA analysis, we were able to identify several improperly tuned antennae as the majority of the problem. A few quick adjustments later, SWR on the important frequencies had gone from about 8:1 down to 1.6:1, and everyone could hear the ops base station loud and clear throughout the venue. Crisis averted!

I keep an rtl-sdr and a NanoVNA in my comm bag for these kinds of situations. What tools do you carry to diagnose issues in the field?