I work for a fire department and just recently took over some radio maintenance. We have had a issue for several months at several of our stations. At night we switch the base stations in the stations to "night call" which only activates the radios for the stations going on a call. When dispatch activates tones and it trips the radio it goes into open mode which allows that station to hear the call and radio traffic. The issue we are having is when the radio is on the "night call" channel and when no one is talking we get a loud machine gun sound that stays pretty constant until the radio is switched to a different channel. We operate on UHF and the only time we have heard this sound is when some of our portables are on scan. Any quick solutions before I have to break down and call a radio shop? Thank you!
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Machine gun sound XPR 4550
- Thread starter patt1345
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Ant9270
The Green Weenie
- Joined
- Aug 31, 2018
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- 493
The only thing I could think of (bear with me, it’s 1am my time) would be that the system transmitting to your radios is transmitting in P25 Digital mode and you’re hearing the raw data packets. That’s the only thing that comes to mind when I read “machine gun” noises. Has your agency recently switched to some sort of a digital system?
I'm thinking along the lines of what GTR8000 is saying. Late at night, you're getting a far station coming in, and its P25.
Since you're the radio guy, why not do a little more research and ascertain what channel(s) the noise is coming in on.
And then ask yourself if it's a channel/frequency that needs to be in the scan list.
Some programmers like to put everything in the radio in the scan list, even the stuff no one cares to hear.
Just because the water department is also on UHF don't mean first responders need to hear the meter readers running around.
One of the things you said in the original post is that it only comes in on portables.
Since it sounds like the base units (and mobiles maybe) don't hear it, take a look at the handheld programming.
Should a tone or digital squelch be enabled on some of the radios, and it's not?
Since you're the radio guy, why not do a little more research and ascertain what channel(s) the noise is coming in on.
And then ask yourself if it's a channel/frequency that needs to be in the scan list.
Some programmers like to put everything in the radio in the scan list, even the stuff no one cares to hear.
Just because the water department is also on UHF don't mean first responders need to hear the meter readers running around.
One of the things you said in the original post is that it only comes in on portables.
Since it sounds like the base units (and mobiles maybe) don't hear it, take a look at the handheld programming.
Should a tone or digital squelch be enabled on some of the radios, and it's not?
cifd64
Member
look at the info provided. Only happens on one channel. Also only happening to XPR subscribers. How are the radios programmed? are they in CSQ or are they PL'd the same as the transmitter? Are they PL'd at all? If there is a digital carrier out there on the same freq, and powerful enough, it can open an analog front-end (XPR's are not as tight as the APX) to where you are hearing raw carrier. Find out how your system is programmed. the general info you provided only allows us to give you a general response. I CAN tell you, that I performer digital IF testing with an analog subscriber. Same frequency. Put the analog into CSQ and yes, it did sound like constant clicking or patterned transmission.
And you’re correct only happening on one channel. Occasionally if my portable XPR 3500e is on scan it will do it, but it defaults back to our main channel. Last night my current station did it. We are a new station and are set up with a Unication G5 pager on the same concept. Our “night call” channel is just a selective call channel programmed into the pager.
TomTN
Member
A local police department has this issue. The officers use Motorola radios. When dispatch began using Hytera radios this problem began and has continued for several years. It only occurs when dispatch is transmitting. Some times the motorboating is worse than others.
So, someone else has changed a variable in your situation, and you are getting a different result than what you have previously experienced. When I see someone make a statement like this (do not take this personally!), it usually means that they lack the prerequisite field skills set and hardware to figure out what has changed, and it is not something that someone on the internets can tell you how to make a quick fix.
As this is for a fire dept and you just took over "some radio maintenance", you should call a qualified and trained radio shop to resolve your issue. If you decide to hack away at it on your own, when your station misses a call entirely, gets retoned, etc and there is a significantly negative outcome after your delayed or missed-entirely response...they are coming after you. You want that? Can you afford to represent your agency on your own?
You should call whomever services your radios and inform them of that problem. There are TENS to HUNDREDS of variables that you will be forced to post on here (most of which will initially be confusing to you - as you may not fully understand what people are asking of you to provide) before those of us that can diagnose / fix that problem for you can help.
This is not "some radio maintenance", this is "system infrastructure modification". Seek professional help from a qualified professional provider who carries appropriate insurance and has the training to do it right, and will continue to work at it until problem is resolved.
All that being said...I had the exact same thing happening to an agency I used to work for. After a tone activation, the station alerting system stayed unmuted for a length of time, and a distant (yet co-licensed) frequency user went digital, and we heard their digital transmissions. I can virtually guarentee that is what is happening to you.
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I have contacted our radio maintenance company and they are checking frequencies for interference. Hopefully the more trained professionals can come up with a solution. I came here to ask professionals if it was a quick fix that someone with basic programming and maintenance skills could understand. I’ll let you know if the analog thingy is affected by that digital whatchamacallit.
Uh you do realize that not all departments have deep pockets and/or have "professional experts" readily available..?
My point is that you went off on the OP over 4 paragraphs when you basically could have stated your last paragraph and been done with it.
I understand what you were trying to say but geez have some respect dude.
I think you read waaaay too much into my response, thanks for your opinion on my post. Have a good one!
I guess those same departments self-represent in court when they have to. $$$ shows up when there is an absolute need for it, mission critical communications equipment falls into that category.
Good idea. They possibly won't charge you for that, but YMMV. Chances are they have seen similar situations and should know how to tailor your infrastructure to alleviate that problem. If they should have to come out to your station, the amount of work they should have to do shouldn't take more than an hour or so to fix, but again YMMV.
I know some companies that won't even charge for that type of change, if it's a simple modification to a unit's programming...they consider it part of upkeep and regular maintenance.
Thankfully right now it's just nuisance noise after a dispatch, think of it a fringe benefit as some extra noise to make sure you are awake and enroute.
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