Batboard

If you're not, you'll probably find this to be long & confusing. Actually, you'll probably find that regardless.

I'm setting up a UHF, 4 channel Startsite system, using MTR2000 repeaters, and MTX838 (MTX8000) UHF radios. Here's my dilemma:

The radios act as if they cannot "hear" the control channels, at least, not properly. I cannot access the system, just get solid bonk tone. Usually, if I power the radios off/on, I can access the system if I PTT within the first few seconds of powerup. This is where it starts getting really weird. Many times, the system will assign the radio to go to channel "3", for example. The #3 repeater will key up, and the portable will transmit, but it will be on a completely different frequency! Of course, the #3 repeater will drop out within a few seconds since it is not receiving the field radio. Using an R2001 monitor, I can see that sometimes the radio is transmitting on one of the other repeater channels, but sometimes it is transmitting on a frequency that isn't even in the system. Occasionally, the system will assign channel "1", and the radios will tx/rx on the proper frequencies. As long as I keep the conversation going between the radios without letting the hang time expire, no problem. As soon as it expires, and the radios have to go to the control channel, I cannot access the system, just solid bonk tone.

Obviously, either the system is putting out bad/distorted data, or my radios are interpreting it improperly. The radios work fine when programmed to another local UHF trunked system, so I rule the radios out. The control channel data looks & sounds fine on my R-2670 monitor. All the "simple" things have been checked, such as ensuring control cables are plugged into the proper ports, connect tone is the same in the controller, repeaters & field radios. TDATA calibration has been performed on all repeaters, etc.

I have my radio codeplugs sent to someone at M tech support, although I'm sure they're ok. I spent a couple of hours on the phone with M yesterday, and a local FTR can't find anything glaringly wrong.

In short, has onyone run across this type of problem before?? Thanks for reading...


Todd

I have had similiar problems with trunking systems where I had to create the codeplugs templates from scratch. Every time I had to do this I had problems with the start & stop frequencies. The radio hears the control channels because they are entered directly, but the radio isn't told which channel to hop to directly. Instead it is told to hop a certain number of channels from the start frequency, which also counts channels by the spacing 12.5/25 on the same screen. Each time I did it, I talked to several people at Motorola technical support to get it right. The symptom sounds right on. I don't have the formula, but it sounds like the place to start looking at. I hope this helps.

It does sound like it might be something like that for the channel assignment, although it wouldn't explain why the radios seem deaf to the control channels as well. I just put in the start & stop frequencies as the lowest & highest repeater channels, is that not the way to do it? It's worked for me on several other OTB trunked systems. I now have all 4 MTR2000 codeplugs off to Motorola as well, hopefully they can come up with something soon. Thanks for the response.

Todd

The one sure way to know if the radio is receiving the control channel is put a scope on discriminator audio. You can see data there instead of white noise if it has locked onto a control channel. Email me direct @ [email protected] and I will talk to you about the start & stops I have.

Ed

Almost sounds like the radios are looking for a different system id. The radio keys up right after turn on because it has found a control channel, and assume's it is the right system, and lets it key up. Once it has time to actually get the system ID than it knows that it isn't the right system and starts scanning for another control channel with the right system ID and now the radio is out of range of a valid system. (If positive subscriber is activated on the controller, this will still happen if your radios fleet and unit id is activated in the controller)
Have had the second problem happen when repeaters are plugged on the wrong port of the central controller. The controller is program for a particular frequency to be connected to a certain port. If the controller thinks port one is say 453.100 and the repeater you have connected there is 453.200, the controller is telling the mobile to go to the 453.100 frequency.


Joe
n1kq

Thanks Joe. Unfortunately, those are all things that have been thought of & checked. I have checked the cabling from the controller to the repeaters, Port 1 is going to repeater 1, 2 goes to 2, etc, etc. The system ID as it is set in the Startsite controller is correct, as it comes up with the proper ID when you log in with CAS (Controller Access Software). ID in the radios is the same. SAC is running with all individual ID's enabled. Connect tone is factory standard 105.88 in the controller, repeaters, & radios. All the "simple" things that I can think of have been checked. There is no reason I, nor our local FTR, can see as to why it won't work. Of course, nobody from Motorola SSC has done anything for me today, tomorrow is going on day 3...we'll see what happens then!

Todd

Thanks Nand. The failsoft idea is one I haven't tried, but will tomorrow. I have set up several other Startsite systems, both 800MHz and UHF, never any problems out of the box until now either. Have disabled all repeaters at one point or another, works the same regardless of which is assigned as the control channel. Have also tried programming the radios with a single control channel (the one which was currently assigned, of course) with no difference.

So far for tomorrow, trying the failsoft & scoping the MTX838 discriminator to see if it's locking onto the control channel. Oh, and giving Motorola $hit for their dealer "support".

Todd

Check the "Base Frequency" on the "birth certificate" that came with the
U48 control plug. The base freq and channel spacing in the subscriber unit must be the same as specified for the controller.
Note that this is specified for REC, and TX. if the code plug is not in the 800band.
This has little to do with the actual frequencies in the sysytem.
The base freqs must be lower than the lowest channel in use.
The radio knows which channel to go to by counting how many channels up from the specified base freq. The channel spacing must be correct or the radio would count two narrow band channels if the spacing were set to 25KC rather than 12.5, or vica versa.
I am familiar with this because High tech re assigned the base freq for a 400 meg US Gov't system with out mentioning it to us. What a circus that was when we installed the new controller.
I wish you luck. Bernie

I agree with bernie. There seems like a definite problem with your frequency definitions, be it base or spacing.

FWIW, I wrote a detailed spreadsheet to aid in frequency defined (OBT) systems. It's available here. You need to have some familiarity with the systems before using the spreadsheet as it can get a bit complex.

Thanks for all the responses, guys. I did end up getting it to work at 4:45pm on Friday, but then had to get out camping for the Canada Day long weekend before I could update the post. Had a much better time knowing I wasn't coming back to a headache on Tuesday!

It did turn out to be a problem with the channel spacing. Even though we were using "wide band" 25KHz frequencies, Motorola did something I've never dealt with before. They set the codeplug in the Startsite to step the frequencies 50KHz at a time, NOT 25!!

For example, another system I set up had frequencies which were separated by 100KHz. They were 25KHz channel spacing, so the codeplug in the controller was programmed to tell the field radios to jump 4 spots to get to the next channel (4 times 25 =100KHZ). But for this system, the frequencies were 50KHz apart, and the controller was programmed to tell the field radios to jump 1 spot to get to the next channel. Of course, I had the radios set for 25KHz channel spacing, so they were only jumping half as far as was required to work properly. Once the radios were set to 50KHz spacing, all worked well.

The worst part is I figured it out before dealer "support" could do it. They called me late Friday night to say they didn't think the problem was with my radio codeplug, and they wanted a copy of the "birth certificate" to look further into it. I was more than happy to tell them not to bother.

I'm still not sure why the radio seemed deaf to the control channel because of this, but it definitely was. I scoped it as per the suggestion of Rude Dog, and I could see the radio settling on the control channel for a few seconds, then continuing to scan for other channels. But, I'm not going to worry too much about it! Thanks again guys,

Todd