Tuesday, March 17, 2015

Desense

I had a little problem with my ham radio setup at home. I figured I'd post about it here just for kicks. I have two "base" radios at home. One is a dual-receive Yaesu FT-8800R that I use to monitor local repeaters. My second rig is an Alinco DR-135 that is connected to my Allstar node. The antenna for my Yaesu is up in the attic above the garage. The antenna for the Alinco was in the garage below.

The Alinco is a 2-meter radio. I run it at 5 watts. When my Allstar node is connected to another node/hub, the Alinco transmits whenever there is activity on that node/hub. The output of the Alinco was essentially "desensing" my FT-8900. The symptom being that the FT-8900 suddenly became "hearing-impaired" whenever the Alinco was transmitting.

I typically monitor the Alinco radio from inside the house on my HT. And 5 watts is way more than I need for that. Unfortunately, regular mobile rigs don't usually go lower than that.

I tried moving the Alinco node radio into my office in order to gain a little more distance between the two antennas. But even on low power the RF got into some of the electronics in the room which made that an unworkable solution.

After considering a number of other possibilities, I decided to take the antenna off the Alinco node radio and swap it with a dummy load. I tried this last night and it seems to work really well. I located the node right in my office and the RF no longer interferes with any electronics. And the dummy load allows enough RF to pass where I can talk though it from my HT with no problem.