Receive Noise on Micor Repeater

rescuer · Post by **rescuer** » Sun Sep 17, 2006 3:22 am

Help,

I finally got my Micor repeater working, somewhat. If I transmit from a portable to the repeater, there is an extremely load "noise" that is retranmitted from the repeater. This noise is so load that it completely overrides the voice transmission. As soon as you let off the mic on the portable, the noise disappears and the repeater tail can be heard cleanly. If you tranmit from the repeater on a local mic the transmission is fine. The problem is not the portables, I've tries 3 different ones all the same result.

It seems like the receiver end of the repeater is injecting pure noise into the tranmitter. I did try transmitting a single tone to the repeater and the audio would pass through. There was some background noise put the audio tone was clearly distinguishable, unlike voice.

Any clues where to start?

Thanks,

Bruce1807 · Post by **Bruce1807** » Sun Sep 17, 2006 6:10 am

Sounds like something is being overdriven on the Audio side.
If the volume contron on the rxer is still live and you are using that to drive the txer, turn it down
Try adjsting the tone into the repeater and see what level of deviation the noise starts. (assuming you have a test set)

Dan562 · Post by **Dan562** » Sun Sep 17, 2006 10:38 am

The first thing needs to known, "Is this Micor repeater set-up for either Tone or Digital PL OR Carrier Squelch?

Do you have the Audio Squelch board's potentiometer set-up for 125 millivolts of AC audio? TRN6007A/B measured on Pin # 11 with a RF Signal Generator set at 100 microvolts, +/- 3.3 kHz Audio Deviation with 1 kHz Audio.

Make absolutely sure that the Exciter's Deviation Potentiometer is set at +/- 5 kHz for Carrier Squelch OR +/- 4 kHz for PL operation with 1 kHz AC Audio on Pin # 7 on the Exciter Board.

The Repeated Audio Deviation Level should be set on the Squelch Gate at +/- 3.3 kHz Audio Devation so +/- 3.3 kHz Deviation In Should Produce +/- 3.3 kHz Out, a pure sinewave. If you do have PL Encoding, remember to Remove the PL Reed or DPL Plug before setting the Repeated Level.

I would recommend having access to a RF Signal Generator and a Service Monitor or a Full Duplex Service Monitor for setting the Audio and Deviation levels.

440roadrunner · Post by **440roadrunner** » Sun Sep 17, 2006 1:57 pm

And in addition to that, Dan, is it a desense/feedback problem? Have you monitored the audio from the receiver with the repeater transmitter both on the air and disabled?

rescuer · Post by **rescuer** » Sun Sep 17, 2006 4:57 pm

OK, OK. You guys are the greatest! I got the audio passing clearly now. It is working really well. Now for the next step, How does one go about adding PL to the repeater station? It was (is) originally configured without PL. I see where the PL card connects to the transmitter board. Does the receive PL connect to the receiver board or is it an option card that connects to the backplane? Anyone have part numbers for what I am looking for?

Thanks again!!!

d119 · Post by **d119** » Tue Sep 19, 2006 9:02 pm

On the MICOR repeater stations, the PL encode and decode is two separate boards that use vibrating reeds to decode and encode the tones.

One board plugs into the receiver, and one board plugs into the transmitter.

There are jumper changes and configuration required on both the transmitter and receiver, as well as the "Squelch Gate" module.

Are you going to be using an external controller with your MICOR, or the factory card cage?

If you're eventually going to hook up an external controller, I'd suggest using the controller's PL encode/decode features (if it's a community-style controller), or using something like a Communications Specialists TS-64...

Setting all those jumpers and finding those parts might prove to be a little difficult these days...