RadioBanter - View Single Post

December 2nd 03, 12:44 PM

On 1 Dec 2003 21:13:04 -0800, (KC2MAC) wrote:

Why is my scanner deaf when I'm transmitting with a separate rig?
Could this have anything to do with near-field emissions? I'm
transmitting with 5 watts of power using a 7.5dB gain omni-directional
antenna. My scanner is always within 10 feet of the antenna.

Yes, the technical, two way trade term for it is desense. One of the
big efforts needed in building a repeater is to isolate the always-on
receiver from the always-on-when-someone's-talking transmitter. They
do that by use of a duplexer and/or antenna separation and
polarization.

Your receiver may not be up to the job, but in any event, its antenna
needs to be as far away from your transmitter antenna as possible. If
the repeater signal is strong enough at your location, you might also
try horizontal polarization for the scanner antenna. That can get you
up to 20 dB isolation from the transmitter antenna, but will cost you
that same 20 dB in strength of the repeater signal.

LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

http://www.woodbutcher.net