Batboard

I've got a UHF MSF 5000 with advanced controller doing PURC. We have an issue with the unit. After the turnon code is sent, which is very stable and straight on the service monitor, the signal for turning on a pager goes out and it becomes unstable (100 cycle wave on the monitor). What adjustment if any can be made to correct the instability of the data?

Analog signals work fine. This is the CLB MSF-5000 and the advanced controller is the TRN7337.

Can one of you MSF gurus give me some help here?

THANKS!

First thing I would try is look at the power supplies with either a o-scope or a voltmeter in the AC position. Look for any AC voltage over 1 volt when transmitting. If you see this, the filter caps are going south on the supply. Had a few of these go bad on MSF 5K 900 stations, noticeable when the TX is on the control channel and none of the clients radios would decode the data.

Second thing is check your data input and make sure your levels are correct. You running POCSAG or ???

Dave

My first thought was a PL signal enabled on the transmitter. Easy to do on a standard MSF5K, but I don't know anything about a PURC.

The power supply ripple or hum should be 60 or 120 Hz, so if it really is a 100 Hz signal, it wouldn't be coming from the PS unless it was a 50 Hz version or being run with 50 Hz power; highly unlikely in PA.

If it is something coming from the PS, then turning the output power to a very low level should reduce the hum and ripple considerably. However, I would expect PS hum to manifest itself as amplitude modulation, which should not be heard on an FM receiver. It would be visible on a scope or a good service monitor.

Bob M.

My two bits worth:
You might look at the VCO compensation adjustment.

Fixed it!

Thanks to all of you for your ideas. After a lot of very tense hours and late nights, things are finally working. I had to find a backup transmitter with an HSO in it. Although it's obvious now, trying to use the PURC's internal oscillator in place of an HSO just doesn't cut it. <smacking head>

Reset the unit to factory defaults, made a couple adjustments and wham, up and running.

The depth of information on this site is amazing. You guys rock.