fire page analysis

[militarymedic22]

Hello,
Have a question for you about determining any differences between two (seemingly identical) broadcasts. More specifically the broadcasts are QQII 2 tone pages for fire/amb. What I have seen happen is with the transition between /\/\ HT1250 to XTS 2500, the 2500 won’t tone alert when a page comes through. This is known problem in the county but so far it seems none of the big communication companies has been able to scratch the surface on what may be wrong. I wanted to post this in the uniden section because I have a 396 unit that I am hoping to use to troubleshoot.
My idea is to try and compare the page broadcast from our com center and one from either our backup com or my 1250. What I don’t know is if the 396 applies any filter that may remove inaudible or data parts of a transmission before passing it to the speaker/audio port. Next, what I also don’t know is what utilities/software would be able to correctly analyze or at least give a readout of the various parts of the page broadcast.
If anybody has any ideas that could help with this… Right now the majority of the county has moved over to the xts /\/\ radios to handle new digital channels. Since all the EMS and Fire people are included in that ‘majority’ we have to either use an additional pager or older radio plus the 2500 to be alerted to pages (when we aren’t monitoring/scanning)

Thanks!

 

[jim202]

Let me start by saying that if you expect much help, your going to need to supply some real details of what you have and what you do now to send out a page. What I mean by this is what band are you using, VHF, UHF, 800.

What kind of a system is it? Do you have a simplex system, a repeater system or are you trying to send the tones through a trunking system?

How are the tones being generated? Is it from a paging encoder or from a console?

Is a control station being used to get the paging tones into your system or are you hard wired to the base station or repeater?

Has a radio tech used a service monitor to measure the audio deviation on the transmitter being used to send the paging tones? If you are using a repeater with a control station, this testing needs to be done both at the control station and at the repeater. Reason I say this is most repeaters are mal adjusted and add too much audio compression to the audio input and distort the audio output of a repeater.

With all the above having been said, you need to understand that paging tones are not sent at the normal audio level of your voice transmissions. This is because if the audio levels of the paging tones were sent at the normal voice levels, they would end up being distorted. When you force an audio tone into compression through a radio systems, you don't end up with the same tone on the output. It can be distorted in all sorts of ways and this makes the detection at the far end by paging decoders almost impossible is some cases.

The industry has learned over the years that tones sent at the 3 KHz deviation level as compared to the normal 4.6 or so KHz of a voice deviation, the chances are that at the far end it will be decoded much easier. If you are using a repeater and the radio tech has added some 2 KHz of audio compression to the throughput, you end up with tone distortion.

The best way to adjust a repeater is to put in a 3 KHz tone and adjust the repeater for no more than 3.5 to 3.8 KHz deviation output tops. This allows the page tones to be sent through the repeater with minimal distortion added to it. Now with narrow banding kicking in, the audio levels are much more critical. All the levels need to be looked at and adjusted for the new set points on narrow band operation.

A simple way to tell if your repeater is not adjusted correctly is to pay attention to the background noise or other people talking when someone keys their mic. You shouldn't hear much that is more than about 2 feet away from the mic. If you do, then either the mic gain on the radio being tested is set too high or the repeater has the audio throughput set too high. Either way, your audio through the repeater is not providing any user the quality it can.

In my many travels around the country looking at radio systems, I have found most radios techs have done a poor job at adjusting the radio systems. The work they do is reflected in how well the radio system performs. The short comings of their work is due to not understanding how important proper deviation audio levels are, never shown how to do it correctly, never reading the manual on how to do it, told by the boss to do just enough to keep the radios working, or just don't give a hoot how the system functions.

If your unlucky enough to be maintained under a maintenance contract, then this becomes even more of an issue. The radio shops are trying to spend the least amount of money on any service call. This means little if any measurements will be done when a tech comes out on a trouble call. They will kick the radio, wiggle a cable or what ever, just to get you back into operation. The days of a radio tech doing a good job have gone out the window with the wind. You need to put your foot down and make them test, fix or what ever it takes to make your system work normally. If this takes going with the radios techs while they are working on your base stations and repeaters, then spent the effort and time to make sure your getting what you paid for in your contract. It may mean getting in the face of the radio shop owner a few times, but do what it takes to maintain your radio system.

I don't make many friends with the radio shops, but I do care how well a public safety radio system functions. Have been in this field for over 45 years now. Been there and done just about everything it takes to build and maintain a system. Stand you ground and get the system fixed.

 

[militarymedic22]

Wow, thanks for the wakeup call jm202!
Unfortunately a lot of the details relating to the actual com center setup are out of my reach. The SO/county prefers to spend tons of money on business coming in and telling them they can’t figure out what is wrong rather than include any of us peons in the group. I know a couple people who are very keen in the radio communications area (fellow military) and could probably lend a very helpful hand. But who am I to argue with the county spending my tax dollars for nothing :-( The project at hand is for the SO’s office to start using digital channels, therefore requiring the rest of the volunteer/private and municipal services to get digital capable radios. On the EMS side, we have been harping on the com center/county about this problem but they have yet to address it. One of the things these companies have also ‘attempted’ to fix is a lot of background noise. The same story of “we can’t figure it out” applies. Since there are so many issues still at hand, the digital transition hasn’t happened yet so we can technically still use the HT1250’s still remaining. ( a lot of them were returned in partial exchange for the new 2500’s)
As much as I like to dig into radio systems, I work only on the medical side. There are some things that I can help with in terms of changing channel lists and minor programming on the radios but I’m not an official coms person by any means. There are some who like to mess around with their personal radios a whole lot more than I do, but they too are not on the need to know list with the coms/county.
What I can tell you is the system is a VHF system, still on 25 (soon to be 12.5) The area I am in relies on the main broadcasting center, but other areas in the county are on repeater towers.
When I mentioned using my handheld for paging, that was simply as a test unit on low power and off of usual freqs to avoid disruption. I would image the com center has a console setup for that, but those are details I’m not too familiar with.
The tones I am talking about for our EMS station in town are 384.4 and 486.6 (the last digit may be off by one or two, but that is the format). The rest of the county follows that same format for their respective tones.
Again, I can’t speak for the specifics of what the county actually did, but I have a feeling whatever base equipment was there before the remodeling was kept and a ‘new face’ was put on top. Who knows, this might be so bad they will have to setup a mobile radio command station and tear out and replace everything in the com center before it works correctly. There is a backup paging system installed in a smaller town in the county, and they can correctly activate the QQII for the 2500’s. I have mentioned that a few times but still nothing.

So besides the fact that I can’t offer that much detail on the system, would you say there is anything that I could do along my initial idea for helping?