Yesterday I had a strange problem with my radio. On the last flight, whenever I tuned it to any higher frequency (ca. above 126 MHz), I heard a constant, very loud humming sound when nobody was transmitting on the frequency. The sound became stronger when I increased the selected frequency. Whenever me or anyone else was transmitting, the sound disappeared and everything was normal. The radio worked fine earlier in the day on the higher frequencies as well (Budapest Info is on 133.00 in my region). It may or may not be important, but I flew both flights in formation with another aircraft. Could they have been transmitting something?
Any ideas what could be the problem?
It is an old Czechoslovakian 720-channel LUN radio, so if any repair is to be done, it will probably be more economical to simply do the exchange to a new 8.33 radio now, instead of doing it next year, but I am still curious what could cause this phenomenon.
Today I flew again (this time not in a formation) and this phenomenon persisted. On frequencies above ca. 126 MHz there is a constant loud noise on the radio, unless I am transmitting or anyone else on the frequency transmits. At those times there is no problem, transmissions are clear and other radio stations report that they hear me clearly. Any ideas?
It certainly makes sense to swap it for a 8.33 kHz capable radio right away, especially if it’s really a 720-channel radio rather than a 760-channel one (that is, lacking the frequencies from 136 to 136.975 MHz). As to the [purely theoretical] question of what may cause this noise, the very first test I would do is try using the radio on the ground, with the engine off, and also with the engine on but the microphone disconnected. I assume you have already tried adjusting the squelch level.
Ultranomad wrote:
It certainly makes sense to swap it for a 8.33 kHz capable radio right away, especially if it’s really a 720-channel radio rather than a 760-channel one (that is, lacking the frequencies from 136 to 136.975 MHz).
Yes, it is. I realized this when I was instructed to contact Prague Information (East) on my way to Rakovnik. It was a funny conversation with Brno Radar for sure. :-)
As to the [purely theoretical] question of what may cause this noise, the very first test I would do is try using the radio on the ground, with the engine off
I will try this.
and also with the engine on but the microphone disconnected
Unable, it is a single plug connector.
I assume you have already tried adjusting the squelch level.
The radio only has an on/off switch for the squelch on the front panel.
