Adjusting Squelch from Centracom?

opskmallory · Post by **opskmallory** » Thu Dec 22, 2005 5:08 am

I have a question. I am a dispatcher for my local public safety agency. We use a Moto Smartzone 800MHZ trunking system which is statewide. On our Centracom Gold consoles we have access to a couple of VHF frequencies. One is our VHF fire paging frequency, which works fine. The other is a statewide VHF frequency, and the third a VHF link to the county sheriff's office (or so I assume...it says our jurisdiction hyphen theirs).

I would like to be able to create a patch from our primary PD channe, or any other channel deemed appropriate, to the statwide VHF. I am not sure that the county link works, since I have transmitted on it and scanned the entire VHF public safety spectrum while scanning and can't find it. Anyway, back to statewide. I am able to transmit to it and receive from that channel using an older VHF radio that the department had lying around. The problem is that the channel constantly has static on it from the console. As soon as I select it, or turn up the unselect volume, I'm getting noise, until I transmit from the portable, at which point the noise goes away and the TX audio from the portable comes through fine. The problem is that because it is receiving a signal, be it only static, when I start a patch, it causes the transmit on the other 800MHZ channel to open and rebroadcast the static coming in from the VHF patch. And because VHF is receiving, the 800MHZ transmissions won't rebroadcast on VHF. So all that happens when I start the patch is that noise gets rebroadcast over 800MHZ and it wont' go away.

So what I need to do is find a way to modify the squelch setting on the VHF channel so it doesn't open until a real signal comes in. This should fix my problem and allow a patch so we can use VHF's radios, in addition to the 800MHZ, should a major incident occur. So, does anyone know how to do this? I'd rather not call the system admin, because A) He'll take forever to get here. B) He will charge us for a visit which honestly is more of a curiosity thing at this point, but if got working, could become a useful tool.

Anyone know how to do this preferrably from the console, or possibly the system control room at the back of my dispatch center? Any suggestions or help would be great. PS, I'm obviously not a Moto tech or anything close; just a user, but I am pretty competent around radios and computers (though I may not be a good speller....competent...compatant...oh, I dunno.)

Thanks

tvsjr · Post by **tvsjr** » Thu Dec 22, 2005 8:33 am

What kind of radio are you using the actually handle the RX/TX? I'm not a Centracom expert, but our Zetron consoles are interfaced to Kenwood radios.

You need to find the actual radio unit and tweak the squelch there, most likely.

Bear in mind, you're playing with infrastructure, which may or may not (and it sounds like the latter) be your job. I wouldn't tweak on anything with supervisory oversight, especially if you're unsure what you're doing, lest you end up explaining to the big bosses how you fried their Centracom or took dispatch off the air.

opskmallory · Post by **opskmallory** » Thu Dec 22, 2005 9:33 am

tvsjr wrote:What kind of radio are you using the actually handle the RX/TX? I'm not a Centracom expert, but our Zetron consoles are interfaced to Kenwood radios.

You need to find the actual radio unit and tweak the squelch there, most likely.

Bear in mind, you're playing with infrastructure, which may or may not (and it sounds like the latter) be your job. I wouldn't tweak on anything with supervisory oversight, especially if you're unsure what you're doing, lest you end up explaining to the big bosses how you fried their Centracom or took dispatch off the air.

Well, to answer your first question, they are running off of Motorola radios; at least that is all I see when I go into the system room. I was not interested in trying to find anything in there to fix the problem, which should address your mentioned concern. I was looking for an option on the console to fix the problem as I suppose if available, would be a somewhat simpler "user level" adjustment which would not require any kind of a supervisor or administrator access. I'm not interested in explaining to admin why I broke everything.

And unfortunately, having looked (I only look with my eyes...not one of those "look by plaing with" kind of people) in the control room have not found anything that looks like a quick and easy fix, thus I have left it alone.

But if there is an easy fix that has been overlooked and doesnt' require the risk of breaking stuff, I'd like to know about it. Thanks.

Post by **wavetar** » Thu Dec 22, 2005 9:40 am

You cannot adjust the squelch level of the radio from the console. It must be done directly at the radio.

It's probably not that simple though, as you're not hearing the constant static when the VHF unit is not patched. Is the speaker icon flashing on the VHF resource icon when you're hearing the static?

Todd

opskmallory · Post by **opskmallory** » Thu Dec 22, 2005 9:48 am

wavetar wrote:You cannot adjust the squelch level of the radio from the console. It must be done directly at the radio.

It's probably not that simple though, as you're not hearing the constant static when the VHF unit is not patched. Is the speaker icon flashing on the VHF resource icon when you're hearing the static?

Todd

Todd, thanks for the reply.

Actually the speaker icon on the VHF channel flashes constantly, non-stop, all day, and if I were to select the channel or turn up the volume, the static would be constant as well. The exception is when I transmit from a VHF portable, in which case the static stops and the TX audio from the portable goes through instead of static.

Does this help at all? Thanks.

TechOps RT-1 · Post by **TechOps RT-1** » Thu Dec 22, 2005 11:58 am

I would suggest contacting a qualified service technician to adjust the squelch on your base station. If you still have any line noise (Not Squelch Noise) after that sqlch adj. proceedure, there are some jumper adjustments on the BIM (Base Interfac Module) in your console that can help, this depending on the current jumper positions and the level of line noise you must attenuate.

Pat

nmfire10 · Post by **nmfire10** » Thu Dec 22, 2005 2:38 pm

Yep. That is problem that must be fixed at the radio itself. If it is old and covered in dust, there is probably a knob on the front of the radio that simply got bumped. I can't believe it has been left like this for so long. If not, it is software adjustable setting that requires the tech to plug a computer into it.

opskmallory · Post by **opskmallory** » Sat Dec 24, 2005 12:27 am

The control room doesn't have regular radios. It's a rack of circuit boards for the radios. Each one is labelled for a specific channel it runs. I couldn't find the part number for the boards, otherwise I'd look for a schematic and find out more. I'll keep checking. If anyone else has any suggestions or know anything about the boards I'm referrnig to, I'd appreciate some info.

As for why it has sat like that so long as commented from the previous posting, my only guess is probably because they've never used it. I've worked here in dispatch for 9 months. I am the only guy, unfortunately, and the only one who has the slightest interest or clue about electronics, computers, & radios. It would also appear I am the only one who even thinks about fixing or changing things...everyone else has the "well it's always been that way so we didn't bother to do anything about it mentality".

I'll probably break down and call our technician, but it will probably end up being after the holidays. In the meantime, suggestions would be appreciated. Thanks.

Post by **wavetar** » Sat Dec 24, 2005 4:49 am

opskmallory wrote:The control room doesn't have regular radios. It's a rack of circuit boards for the radios. Each one is labelled for a specific channel it runs.

I believe what you're describing is the CEB (Central Electronics Bank). The boards you are referring to are probably BIMs (Base Interface Modules). They are essentially fancy tone remote cards, and they in turn interface through leased phone lines to the radios out in the field somewhere. So, you'll need to find somebody who knows where the actual radio is, before they can adjust the squelch & fix your problem. If it's a 'statewide' frequency, it's likely a high powered transmitter sitting on a very high hill, with a very tall tower...possibly with satelitte receivers & a voting system in place for it too. I recommend having your system maintenance provider deal with the issue.

Todd

440roadrunner · Post by **440roadrunner** » Sat Dec 24, 2005 11:40 am

I'll probably break down and call our technician

I don't want to sound to negative to you, but that is just an excellant idea.

There are far too many people fiddling with this equipment that is far beyond their means. Some of this stuff can get incredibly sophisticated, complicated, as well as intertwined with other issues. Sometimes what seems to YOU to be a receiver, "isn't." I was once envolved with a large voted system, transparent to the operators. What the operators "thought" they heard as "one receiver" was actually a county wide bank of voted receivers, actually being relayed to a central point by everything from hard phone lines to fiberoptic to microwave links, as well as UHF radio links. When the operators reported a problem such as you describe, most of them had no idea of the complications of the actual system.

There are a host of issues that can cause a seemingly simple "loose squelch", including but not limited to, on channel interferance, noise generated by some piece of equipment, deliberate interferance, and "mixing" by two (or more!) unrelated transmitters. There can be something actually wrong (failed) with the problem radio, as well as an adjustment, or possibly even a "drifting" situation, caused by such things as changes in temperature at the location of the receiver. Antenna, duplexer, and combiner problems can introduce problems, too. It might just be a far away station on channel, whether it's supposed to be there, or not.

Sometimes the problem can be "solved" by using or changing squelch coding.

Dan562 · Post by **Dan562** » Fri Dec 30, 2005 11:58 pm

I can't believe the last post by "440roadrunner" ... "Go ahead and call your Radio Maintenance Technician but I'll give you Fifty excuses why the technician can't resolve the squelch problem!" It makes me wonder if your "opskmallory's" Radio Maintenance Technician?

I think opskmallory has been more than patient, 9 months with the "open squelch / noise problem." If the Radio Maintenance Technician and/or Service Shop can not correct or solve the problem in a timely manor, they should provide a clear concise document why. Generally, if this is a Public Safety Trunking System, there are "Service Contracts" written, provided and signed by the Service Organization and high level management within that Public Safety Department for 24 x 7 by 365 days a year for these exact type of complaints and/or problems.

If the manufacture's service organization is not fulfilling their contractual responsibilities to this Public Safety Department then the Lawyers step in and draw up the necessary documentation for court approved Big $$$$$$$$ Lawsuits. I'll guarantee when the service organizations receives a Lawsuit for not providing their said services, there will be huge snowballs rolling down hill even in the middle of Death Valley, California, in the dead heat of summer. Surely you do not want to be anywhere near the legal problems as they unravel!

440roadrunner · Post by **440roadrunner** » Sat Dec 31, 2005 9:45 am

can't believe the last post by "440roadrunner" ... "Go ahead and call your Radio Maintenance Technician but I'll give you Fifty excuses why the technician can't resolve the squelch problem!" It makes me wonder if your "opskmallory's" Radio Maintenance Technician?

I do not understand your statement here--I'm not offering any excuses why "it can't be fixed" I'm merely attempting to point out that fiddling with squelch adjustments by the operators are not always the fix. The point is, to identify the REAL problem and fix THAT

[/quote]I think opskmallory has been more than patient, 9 months with the "open squelch / noise problem." If the Radio Maintenance Technician and/or Service Shop can not correct or solve the problem in a timely manor, they should provide a clear concise document why

Maybe I'm missing something here, but I don't see anywhere that the operator in question has contacted any service people.

I can see nothing he has said about complaining to technicians, but is rather contemplating use of some VHF channel, that has a possible problem

Adjusting Squelch from Centracom?

Adjusting Squelch from Centracom?

Agreed