---------------------------------------------------------- Avionics-List Digest Archive --- Total Messages Posted Sun 09/04/11: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 04:34 PM - Re: Re: Hum in Radio? (Doug McNutt) ________________________________ Message 1 _____________________________________ Time: 04:34:17 PM PST US From: Doug McNutt Subject: Re: Avionics-List: Re: Hum in Radio? At 17:13 -0700 9/3/11, Goodone wrote: >I would say that the "hum" that I am hearing is about one octave below middle C. It sounds a lot like the noise that you hear when folks are having trouble with feedback with a microphone in a nightclub. I doubt very much that it is from some noise source on the ground. Maybe it is being generated from something in my aircraft that I do not hear while in the air. I also don't think that it is from a bad connection in my antenna since I do not hear it at all on the ground when I am on the grass strip that I operate from. I have never played with an Icom IC-A24 but I suspect that it has an automatic squelch scheme that is supposed to turn off received audio until there is a sufficiently large signal coming in on the selected frequency. If the squelch is set too low it's conceivable that it works properly at your home base where there may be only a tiny bit of RF activity in the neighborhood. On a large airport there may be a lot of transmitters such as ILS equipment or radar that are "breaking squelch". That kind of noise would not usually get described as hum. But ILS and VOR use low audio frequency modulation tones that might come thru. If your receiver has a squelch control you might need to adjust it differently. If it doesn't there is probably an internal adjustment that could be mucked with but somewhere it will say that needs to be done by a man with a radio license. It isn't true though so long as you don't tune the transmitter. Someone on this list probably knows about that particular radio. OK on grass strip plus NG on a big taxiway seems to rule out something in your aircraft power system. -- -->A flashlight: is a metal tube used to store dead dry cells. <-- ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message avionics-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Avionics-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/avionics-list Browse Digests http://www.matronics.com/digest/avionics-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.