On 9 Jul 2004 08:11:40 -0700, (ScanGwinnett)
wrote:

I'm using a Stridsberg antenna multicoupler to connect three scanners
to the same beam antenna. The audio of each of the three scanners is
fed to the line input of three separate computers.

You say three scanners.

As far as I know, John S, makes a 4 input multicoupler. If you have a
4 input unit and are using only three, make sure you terminate the
unused input.

Use a formal terminator (cheap) for best results, or solder a 50 ohm
resistor across a make BNC if nothing else. Don't use a 75 ohm
terminator such as is used in CCTV systems.

Unused and unterminated inputs in a multicoupler can cause
unpredictable results.

Also call John Stridsberg and ask him. He knows his product. I expect
the first thing he'll tell you to do is terminate any unused input and
get back to him.

After I connected the scanners to the multicoupler I noticed that in
the audio of each of the scanners you can hear the audio of the other
two scanners (but at a much lower volume). If I disconnect the
scanners from the multicoupler and switch to separate antennas the
problem goes away.

Make sure you don't have ground loops. Look for bad coax shields on
all RF coaxes. If signals can't find the path they expect for the
return line, they'll force their way through the equipment.

Swap stuff around and try to narrow the problem down to one component.

Is there something I can do to prevent the audio from each scanner
completely separate from the other two scanners?

I've used many of John S' couplers and not had this problem.

I suspect you have a ground loop (open ground) in the RF or audio
wiring. Find and fix that and your problem will clear up.

Steve


************************************************** *******************
Steve Uhrig, SWS Security, Maryland (USA)
Mfrs of electronic surveillance equip
website http://www.swssec.com
tel +1+410-879-4035, fax +1+410-836-1190
"In God we trust, all others we monitor"
************************************************** *******************