Overmodulation Question

[d-hughes]

Our county dispatch uses an older radio/paging system.

We currently are using a MIP 5000 radio console that was transmitting over a private copper trunk to our communications tower using a VFH analog radio system. The output from the console is converted with an MIP 5000 Gateway. The old run is about 2.5 miles over these phone lines. Over time the copper has degraded, and there is excessive noise and ground hum on the lines.

In order to correct this, a vendor installed a bank of mobile radios that now converts the signal from the gateway via a CPI TTP216 system to something that the mobiles (XPR 5350e) can use over a copper run of about 10 feet. The problem is that the signal being broadcast to the tower is severely distorted. The TTP216s have had the TX MOD and LINE AUDIO adjusted all the way "down". While this mostly corrected the severe distortion to minor distortion, the page tones for Fire Rescue are still severely distorted (as these are louder than the normal voice communications). Now our problem is the page tones (QCII) are not being properly interpreted by the portable radios (XPR7550) that the fire department uses. The Minitor V pagers sometimes work.

Our goal is to replace the entire system and all radios. This is several (3-5) years out due to cost and other ongoing infrastructure projects. What we need is a way to fix this in the interim. Our vendor views the entire system as "antiquated" as almost all the components are discontinued. And in classic style, they would rather sell us a replacement system rather than troubleshoot and fix the system we have now. I am currently wondering if the shortened distance of copper is causing the increase in signal being dumped into the mobiles causing this distortion. I am hoping to find ideas for a short term solution that I can give to the vendor while we are in the process of designing and funding the new system. Any input would be helpful.

 

[prcguy]

I think someone with system manuals that show typical audio levels into the radios should check things out with an oscilloscope. Inject a few tones, measure levels, look for distortion at different points in the system.

 

[a417]

If it affects signaling in a life-safety system, as fire dispatching should be regarded, the in-place vendor needs to remedy the problem. If they can't - or are unwilling to step out of the comfort zone - to solve the problem that many agencies are dealing with regarding legacy hardware, another intermediary vendor/troubleshooter should be brought in who can and will fix the problem. I would view this as an unacceptable life/safety risk and would hold the vendor accountable. If the vendor is still unwilling, the municipality needs to be made aware - as substandard services will continue until they remedy the problem or find someone more willing.

There is legacy hardware all over this country, and there are vendors all over this country that are familiar with it and can do stop-gap to hold people over or solve shortcomings and failures. Sounds like this vendor isn't one of them, and I would advocate for replacing them. If they can't to even the most basic of audio adjustments over 10 feet of local copper, what else can't they do?

Not popular opinion, of course, but I'd hang them out to dry.

"Hey Town Manager, you shouldn't pay this bill for this console work until they solve the tone alerting problem. 40% of the times the crews aren't hearing the calls go out" ...watch what happens.

 

[TampaTyron]

You could replace the MIP to tower connection with a couple of Omnitronics boxes that take 2 wire or 4 wire in one port and push it over IP to the other box, which then recreates the analog audio and tones. This requires IP between the two locations. You could also have a tech over 45 years old come out and adjust the audio levels of the equipment in its current config. Keep calling shops, call other agencies, find someone to help. Do not just replace the equipment based on a single vendor trying to force the upgrade. TT

 

[RFI-EMI-GUY]

It indeed sounds like the vendor neglected to adjust the transmit levels of the console and/or the transmitter drive from the TTP. I also see that default has an AGC which may be overkill for your locally connected solution.

For reference, I have attached the manual for that CPI Tone Termination Panel.

https://www.cpicomm.com/216manual.pdf

I am with a417. The vendor needs to send their best guy out to adjust the levels to test tone.

 

[RFI-EMI-GUY]

Our vendor views the entire system as "antiquated" as almost all the components are discontinued. And in classic style, they would rather sell us a replacement system rather than troubleshoot and fix the system we have now.

H /\/\ /\/\ , I can only guess who that might be!

 

[a417]

Town Managers and Finance Directors love this kind of stuff. They take heat every day about how much money they spend from the constituents, and if they have the ability to torch some abusive vendor who is feigning ignorance or apathy with money - the horns come out real quick. I've heard some of the more professional sounding eff-yous come from them, and the those balance due checks will sit there until they are satisfied. If they don't fully understand the dynamics of the problem, you might have a new best friend for a while who wants to know why you are bringing this concern to them - and then what you want done to solve it.

 

[mmckenna]

Our vendor views the entire system as "antiquated" as almost all the components are discontinued. And in classic style, they would rather sell us a replacement system rather than troubleshoot and fix the system we have now.

That's the sign you are speaking to a sales oriented person and not someone that knows how to fix things. Try another shop. This does sound like a level setting thing and it sounds like the tech they sent out didn't understand how to do it.

I am currently wondering if the shortened distance of copper is causing the increase in signal being dumped into the mobiles causing this distortion. I am hoping to find ideas for a short term solution that I can give to the vendor while we are in the process of designing and funding the new system. Any input would be helpful.

Unlikely.
If these were copper phones lines from the phone company previously, the levels would have been set for that. The telephone company techs would set their levels/eq through their equipment so it would be essentially invisible to your system.
This sounds like someone came out and installed the equipment but didn't understand how to adjust levels all the way through. When they didn't know what to do, they just tell you that you need new equipment. That's lazy.

 

[RFI-EMI-GUY]

Town Managers and Finance Directors love this kind of stuff. They take heat every day about how much money they spend from the constituents, and if they have the ability to torch some abusive vendor who is feigning ignorance or apathy with money - the horns come out real quick. I've heard some of the more professional sounding eff-yous come from them, and the those balance due checks will sit there until they are satisfied. If they don't fully understand the dynamics of the problem, you might have a new best friend for a while who wants to know why you are bringing this concern to them - and then what you want done to solve it.

Indeed I have been on the wrong side of that equation when /\/\ shipped some crappy sounding STX-821 radios. The City Manager had came from another city and he knew exactly how they should sound. /\/\ installed some "50 Cent speakers" (As the client stated) and they were tinny and distorted (crossover dist. diode fix). It was a huge check I eventually collected, worth more than my house. I am sure the City enjoyed the bank interest.

 

[NVAGVUP]

Don't know the MIP5000. But some console systems send out voice and paging tones "flat". (This is an issue) GOOD console systems will send out vx flat and deemphasize the paging tones.

If the console sends everything flat, it is possible the phone lines had poor frequency response. (Which may have benefitted tones in this instance) Direct connecting to radio negates possible freq response issues. But if your tones are higher freq (EX 1K and higher) these tones will modulate significantly higher than vx (especially male voice)

Fixing/maintaining these systems was my bread and butter in my previous life. If your vendor/techs do not understand pre-emphasis/de-emphasis, you need to move on.

 

[radiodog2009]

Our county dispatch uses an older radio/paging system.

We currently are using a MIP 5000 radio console that was transmitting over a private copper trunk to our communications tower using a VFH analog radio system. The output from the console is converted with an MIP 5000 Gateway. The old run is about 2.5 miles over these phone lines. Over time the copper has degraded, and there is excessive noise and ground hum on the lines.

In order to correct this, a vendor installed a bank of mobile radios that now converts the signal from the gateway via a CPI TTP216 system to something that the mobiles (XPR 5350e) can use over a copper run of about 10 feet. The problem is that the signal being broadcast to the tower is severely distorted. The TTP216s have had the TX MOD and LINE AUDIO adjusted all the way "down". While this mostly corrected the severe distortion to minor distortion, the page tones for Fire Rescue are still severely distorted (as these are louder than the normal voice communications). Now our problem is the page tones (QCII) are not being properly interpreted by the portable radios (XPR7550) that the fire department uses. The Minitor V pagers sometimes work.

Our goal is to replace the entire system and all radios. This is several (3-5) years out due to cost and other ongoing infrastructure projects. What we need is a way to fix this in the interim. Our vendor views the entire system as "antiquated" as almost all the components are discontinued. And in classic style, they would rather sell us a replacement system rather than troubleshoot and fix the system we have now. I am currently wondering if the shortened distance of copper is causing the increase in signal being dumped into the mobiles causing this distortion. I am hoping to find ideas for a short term solution that I can give to the vendor while we are in the process of designing and funding the new system. Any input would be helpful.

Is anyone in your area using APCO P25, Phase 1 or 2?

This seems to be the gold standard in law enforcement communications. It allows agencies to have the ability to talk with others across the system to solicit help or transmits BOLO's to a much larger audience.

I hope this helps.

 

[ElroyJetson]

Who owns the copper lines? Are they leased or owned by the agency? If they're leased, then the leasing company probably is contractually obligated to provide a defined level of performance (quality of service clauses) and if the service quality falls short, it's up to them to remedy the situation or be at risk of legal action.

At this point, it'd make sense to abandon degraded copper cables and go to fiber. Microwave point to point links are also a viable option and likely the cheapest.

Integrating analog paging into digital systems has so far proven problematic, based on how many times I've heard of this causing problems.
I look forward to the day when the industry has SETTLED on an effective means of providing analog paging functionality within the context of fully digital systems.