Batboard

Hi Group,

Getting ready to interface my MSF 5000 CXB Digital station to a special type of external repeater controller.

I need the following signals:

1. flat, unsquelched discriminator audio

2. Modulator audio or source to inject flat audio

3. Push-to-Talk

4. PL indicate that goes low upon PL detection

5. Ground

Anyone have any suggestions?

Thanks!

Start here:

http://www.repeater-builder.com/motorol ... index.html

There are a couple of articles on that page that should give you some signal locations to try. Also, schematics of the SSCB will be quite helpful as there are jumpers you can remove and attach your own signals to, bypassing some of the existing circuitry.

Flat RX (discriminator) audio is easy. Flat TX audio might be more of a problem.

Bob M.

OK. I'll check this out.

I'm interfacing to a Palomar Telecom controller, in case anyone else has done this...

I'm unclear on where to get the PL indicate signal from a CXB control shelf - I need a signal that goes low on active and doesn't exceed +5v.

I'm sure all the signals you'd need are there, but you may have to invert one or two. A couple of 4.7k resistors and a common NPN transistor can do that for you. Almost everything on the SSCB runs on +5V, or your controller probably has that floating around.

With the schematic, you might find that the correct polarity signal is present if you go backwards to the input of an IC.

Bob M.

J2900 pin 8 (on the TTRC) goes low when a signal with the proper PL/DPL is received. You'll need to supply your own pull-up resistor to +5V if the controller doesn't already have one.

There's no separate PL/DPL detected signal floating around, as the microprocessor does that in software and uses it internally as a PTT qualifier for the various modes.

There is a separate COR signal that really should be called receiver active, but it goes high with carrier. Your controller might be able to deal with that.

Bob M.

Bob,

I'll investigate this. This information re: J2900 Pin 8 TTRC is good for CXB Digital stations, correct?

Thanks!

Yes, you won't find a TTRC on an analog (CLB) station.

There might be a cable plugged into this connector already. It would run to a DB25 jack on the station junction panel. I just unplug the cable at the TTRC and make sure it's out of the way when the control tray is closed.

There are a few articles over on repeater-builder.com that deal with MSF5000 interfacing. They're all worth reading.

Bob M.

There is a jumper on latter-revision SSCBs that is a PL indicate signal. It comes directly from an ASIC. It is labeled 'JU18' - I believe the center of this pin, properly buffered by an NPN transistor, will be just what the doctor ordered. The other method is use of the TTRC board's programmable pin for MUXA3B2 (IIRC).

JU18 has been confirmed to perform the desired function of PL/DPL indicate. IIRC, it's a high true signal - perfect for driving an NPN to buffer & invert.

Will have to reconfirm this data when I return home...

I have a small bit of work to do on a comprehensive answer for d119's interfacing questions.

-KGB

OK. Let me know what you find.

I managed to locate all 22 jumpers on the schematic. Some are used for dealing with a community tone panel, others let you insert tone or data directly into the audio chain.

Unfortunately, the manuals only refer to the "normal" and "alternate" positions of these jumpers. There's nothing on the schematic that indicates which position is which, unless you assume that they are shown in their normal position, and I don't recall seeing a note to that effect. The images of the board don't help either.

You might find adequate spots to pick up, or inject, signals to your liking if you examine the schematic and then go look at various pins on the ICs with an oscilloscope under conditions with and without signals. It won't be easy, and you'd have to be careful about loading some signals and AC-coupling others. Also, take care not to short anything to ground or any other voltage. At least the user-accessible connectors are somewhat well documented and provide some protection for the rest of the station.

Bob M.