MC2500 Deskset

[johnny1225]

I have a MC2500 Deskset hooked up to four different hospitals. 3 out of the 4 are working very good. The fourth Hospital seems to intermit. Sometimes it will work for only 10 minutes, sometimes 1/2 hr, sometimes longer. It seems when they transmit from the base i.e the MC2500 the hospital can hear them, but when transmitting back the MC2500 cant hear them. Equipment wise they are using XPR6350 UHF radios in digital mode. They are using a control station a XPR4350 Mobile base hooked to a MR200 tone adapter made by CPI. We have had the phone techs at the hospital and also the phone provider look at the lines with them saying the phone lines are in great working order. With three out of the 4 hospitals working great without a issue and only one hospital intermitting i suspect the MC2500 is working fine. Can anyone spread some light on this situiation for me to see what my next step would be. i.e adjusting something in the MR200 tone adapter..

Thanks

John

[RFguy]

What's the audio level in dBm of the recieved audio at the MC2500 on the problem channel?

What are the receive audio levels in dBm on the working channels?

[guy being a guy]

27 years experience as a Motorola system tech ...........

I can tell you now its the phone lines ! It happens (intermitants) during the summer months - heat , copper expanding and contracting over miles and miles of its length. The phone "people" have their own specs of acceptable loss which is all they will admit to and care about . Many techs don't even really know the old copper stuff anymore - I have to assist them ALL the time in troubleshooting the lines. They MUST go to BOTH demark punchblocks and shoot tones down the lines. I've had them pick points miles and miles away from the actual demark point and sure enough its a bad connection right outside my tower site or something.
Anyway .........Fighting and arguing with these guys is a waste of time ...........Simply go into your desksets line settings for this channel that is giving you a problem............slightly increase your TX levels going down that line. Check back in the next day or so and see if it has gone away. If not, then I will really crank them up on my next visit - did it go away ? No, than the line is completely intermitant to that site - call the phone guys and have them look at the line. Yes, it went away - phone line is just a crappy , lossy line and aruguing is a waste of time as it will get you no where ! THEN start decreasing the TX level to where it gets around the loss of the line and is operational.
I have also just asked them ( the phone company) to simply give me a ENTIRELY NEW circuit as this one is crappy and I'm tired of it. Quicker, easier, solution to intermitant lossy , copper circuits.

I also had a time where I did an inventory of about 200 circuits for a customer that had intermitant crap happening for years. I found a mix of analog and digital circuits. Each one has a different acceptable loss and cost per month. ALL my intermitants were on the old analog circuits with higher acceptable losses Changed them all to digital cuircuits and spent 2 weeks TURNING DOWN all my levels ! Huge difference, and one happy customer.

I also am assuming that the repeater and local adapter are fine - I will bring my own simple tone deskset with alligator clips and attach to the punchblock at the transmitter site. Keep keying over and over until you are satisfied that nothing there is giving you the problem at the site.

[guy being a guy]

Oh , yeah another way to troubleshoot that I forgot ...........
Go to both ends of the line and REVERSE the copper pairs. Swap the pairs TX and RX.
Now you have intermitant RX at the deskset and you can TX fine - BAD PAIR !
Just get them to give you a new circuit and spend your time doing something worthwhile !

Add up the yearly cost of leasing these lines and quote them a microwave backhaul link and be done !
Use the cost spreadsheet and all the time and money you bill them plus the questionable reliability of these leased lines and most customers will shell out the money for a microwave link.
I also inform them that I am strapped to the phone company on this issue, so if it goes down at 2am and the phone company won't respond to my service request for 2 days ,then your screwed for 2 days !

[Jim202]

Where are the line level test sets? How can anyone say the lines are OK if they don't provide what the actual line level losses are?

How can you say that you just go in the next day and crank the line level up some? Just how much did you crank the line level up? If you don't put a TIMS unit on the line to make any measurements, how can you say anything about just what the line level actually is?

To do this correctly, you need 2 people. Both need a test set that can both send and receive a tone at a specific level. Unless you have a calibrated test unit, it would be good to set both units together and measure just what each unit is showing. That way you know if what your sending or receiving is correct.

It sounds like we are seeing the early stages of technicians and their skill sets on this issue. Remember that today, there are very few copper circuits left in service. Most of the radio control circuits today are audio only. So there is a 4 wire audio amp bridge unit at the end of each phone circuit. Don't forget that at each central office these circuits go through, there are additional 4 wire audio bridges. Each and every one of them needs to be adjusted correctly in order to get the correct levels at the far ends.

Another point to remember here is that the phone company doesn't like to see any levels above the zero db point. It does cause cross talk between circuits. If you crank your levels up too high, you might find that the circuit has been disconnected because it is causing problems for others.

I try and use a negative 3 or negative 5 db when I try to do an end to end measurement. The phone company also will not set their circuits for no loss. Expect to see at least a 3 db drop end to end. So if you inject a negative 3 db 1000 Hz tone in one end, you should see it come out at the far end between negative 6 and negative 9 db on a good day. If your seeing more loss than that, get on the phone company to fix it.

As for this problem between the different hospitals, I would have to actually see what the line level measurements were before much more can be said. Please provide the test results so you can be helped. Don't forget that when making these measurements, it makes a big difference if your test unit is in the bridged mode or the terminate mode. It also makes a difference if the remotes are still connected to the circuit when the testing is done. This is why the test technician needs to know if the equipment is still on the line, so he knows how to set his termination to either the bridged mode or the terminate mode.

Let us know how you make out on this problem. Keep the board here informed.

Jim

[desperado]

Gotta say that the test sets (TIMS or Transmission IMpairment Set) is the ONLY way to properly test a set of lines.
Get a set (meaning 2 test sets)
You use one to generate tones across the lines. You start at a specific level (under -10 phone people get all concerned when you are cross talking tones on their pairs)
you inject -10db at one end and look at the line loss at the other end. If it's more than say 10 db, then the line is faulty.
Simply throwing a tone generator on one end and listening for the tone at the other end is NOT a test. Those are for line identification, not testing a line.
Tone generators will pass tone on a near shorted pair, try it if you doubt me.

Once you have pair of TIMS sets and can tell the phone clown that his lines have 30 db of loss on them at 404, 1002 and 2800 and need to be properly repaired they will look in bewilderment and cuss you before asking an old timer and getting told those are the three telco repair tones and to get busy fixing it.

[CPIComm]

johnny1225, did you ever get this problem taking care of?