Andrew Dickens wrote:

Thanks for your help. The regulator was good. We swapped it with a brand
new one and it did not fix the voltage drop (13.5 down to 9). Replacing the
power supply fixed it. The power supply that failed was the factory
original. The replacement unit was pulled from our other STL transmitter.

Right, but what was wrong with the power supply? Knowing what was wrong
with the power supply might tell you a lot about what is going on.

The second unit - the one that exhibits noise has a constant white noise
that can be heard during both quiet and loud periods. It also has a raspy
high frequency distortion that you can hear, particularly when someone is
talking.

If you return the new power supply to the other transmitter, does the problem
follow the new supply?

Is the received signal strength on the receiver good? If you listen to
the signal with a scanner right in front of the transmitter, do you hear
the distortion on that as well?

If you're hearing a higher noise floor AND distortion, that makes me suspect
that the signal strength isn't high enough to get full quieting on the
receiver.

If you put a wattmeter on the transmitter output, are you seeing good
deflection? What if you use a dummy load?

Your first goal is to isolate the problem and make sure it really is the
transmitter and not the receiver. Your next goal is to make sure you are
getting full power output from the transmitter. If so, it's probably a
modulation issue.

It is not a line echo. But the sound is similar to a bad long distance
connection, where you say something and hear a distorted version summed with
it.

Does it sound like fringe FM reception?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."