I agree with Nate. Sounds like intermod and since it sounds like a buzz it may be mixing with a digital transmitter.
Dave Baughn
Director of Engineering
The University of Alabama
Center for Public Television and Radio
WVUA/WUOA-TV & WUAL/ WQPR/ WAPR FM
Box 870150
195 Reese Phifer Hall, 901 University Blvd.
Tuscaloosa, Alabama 35487
205.348.8622 cell 205.310.8798
[EMAIL PROTECTED] KX4I
>>> Nate Duehr <[EMAIL PROTECTED]> 10/1/2007 12:34 PM >>>
jminn699 wrote:
> -I am having the same problem also with a wacom duplexer. On a dummy
> load the tunning checks great with no desense, but with the antenna
> attached the repeater will hang on transmitting noise as long as the
> ttansmitter is on.
Are you sure you're not just mixing with another transmitter/something?
How do you know it's the duplexer if you haven't swapped it out with a
borrowed one, or something similar?
External mixing out in "the world" around the antenna would do the same
thing you're experiencing.
Anyone install anything physically near the antenna that has crappy
grounding and/or loose metal on it?
> I can`t take the system off the air, and I don`t have another
> duplexer. My short term solution has been to set the repeater hang
> time to zero. Another would be to make the tx pl different from the
> rx; but I am hoping to avoid reprogramming all the radios on the
> system.
The split-PL just covers up the real problem. If the receiver is
hearing the transmitter -- you gotta fix that.
Have you observed how much the problem changes when you lower
transmitter power? If it's mixing, it'll drop off quickly, since that
slope is steeper... if it's external and your antenna is just "lighting
up" something that's acting as a diode at RF.
> My system is located in a lousy enviorment, a elevator equipment
> room-there is a layer of carbon dust on everything. I suspect that
> this dust may have found its way inside the cans, but I can`t take it
> off the air to open up the cans.
If you can't take it off-air to fix it, how are you ever going to fix
it? :-)
> I hope someone has a solution to this problem.
Welcome to IMD hell. :-)
Time to hunt with a spectrum analyzer... see if you can find another
high-power transmitter on-air nearby that correlates with the times when
your receiver hears your own transmitter.
It's not fun. But if you just started experiencing this and it was
working prior to that, something changed. Look for new antennas, new
transmitters on the site, etc.
Nate WY0X
