Analog Voting vs. DMR

[zap]

Happy New Year's Eve

Interesting problem that I am incurring here. I was consulted (by the shop making the sale) about a school district wanting to go to a voting system on a single analog pair. From what I've been able to discover, there are ~500 portables in use district wide (UHF), the district is already licensed for 4 different pairs. Majority of the traffic is simplex however, ISD PD uses the existing (EF Johnson?) repeater. The problem is that the PO's can not access the repeater from in the building but as expected, it is full quieting into the building. Outside, the system is usable from the subscriber POV. Somone, unsure of whether it was the shop or district, said voter and that's all anyone wants to do now. However, the other criteria is that a solution must backhaul over an IP network. This is a sale that Icom walked away from...

Anyway, my colleague suggested a Raven IP voting solution with an Icom receivers. I suggested, if the system must be voting, to use the Raven solution with Hamtronics receivers instead.

Then we were given to other little bits of information. The subscribers were most likely near end of life and the administrative staff would also like to be able to use the system. From that information I suggested a DMR Tier 2 system with Roaming using low power "campus" repeaters all linked together. One time slot for PD...another for everyone else (if they want it). Was also thinking about scaling the system for mixed mode operation allowing DMR to be phased in as needed and once analog was phased out...move Tier 3 (possible).

Anyway, what would the readers here on the forum do if in a similar situation (I'm assuming budget is limited).

 

[com501]

Forget mixed mode, you cannot link repeaters together in that mode, and it doesn't work that well anyway. Have them start by buying subscriber units that will do DMR (Motorola would be best) and continue to use their existing systems until the get enough units to switch to digital. Replace the repeaters with new digital radios in the locations where you need them, run them analog for the interim if you have to, but plan on going to IP site connect at some point within a short period of time. Get them on new infrastructure with a working system and they will be much happier.

Do not forget the power of lease/financing or grant money for public safety/terrorism/mass casualty procurement paths, either. Nothing like pictures of a Sandy Hook type tragedy to bring home to a district office that fact that their radio system doesn't cover their needs.

 

[zap]

Forget mixed mode, you cannot link repeaters together in that mode, and it doesn't work that well anyway. Have them start by buying subscriber units that will do DMR (Motorola would be best) and continue to use their existing systems until the get enough units to switch to digital. Replace the repeaters with new digital radios in the locations where you need them, run them analog for the interim if you have to, but plan on going to IP site connect at some point within a short period of time. Get them on new infrastructure with a working system and they will be much happier.

Do not forget the power of lease/financing or grant money for public safety/terrorism/mass casualty procurement paths, either. Nothing like pictures of a Sandy Hook type tragedy to bring home to a district office that fact that their radio system doesn't cover their needs.

Actually, Hytera and Simoco infrastructure both allow for linking in mixed mode and analog forms.

 

[com501]

I've never heard or seen anyone with a Simoco radio in 40 years of two-way, but some hams have Hytera stuff. You might be able to link the repeaters, but you can't switch back and forth between digital and analog and have working IP site connect, it just won't work. I think I see why Icom walked away.

500 units is a fairly robust district. They should start thinking in terms of real serious equipment and not bandaid solutions. How much would ONE negligent death lawsuit cost them in this day and age?

 

[zap]

Don't know. My understanding is currently the campus LEOs are the only ones using the repeater. The district would like admin to be able to use as well but currently 480+ handhelds are used only for simplex.

I held a Simoco radio before I even got in the business…even have a P25 repeater on loan sitting in my shop at the moment. Simoco being a European company has some different stances on adverising…which is why they don't.

But yea, I see your point about mixed mode.

 

[Bill_G]

Voting was invented to provide a good inbound path from low power portables to a central base or repeater. Works well for that purpose. It definitely improves mobile communications. But, it does nothing to improve the outbound where building penetration, or poor coverage areas can be an issue. Analog voters are dependent upon analog voice paths. ie: phone lines, or TDM with very low latency. When you attempt to use IP devices to carry voice grade audio to an analog voter/comparator, you run into problems with intermittent frame loss causing distortion in the receiver pilot tone that causes falsing, or in the keying tones dropping out to the transmitter causing it to dekey. You can increase the receive buffer size in some IP devices, but not all. You also have to worry about the high frequency noise content of the inbound signal. All comparators are dependent upon that noise to determine which receiver to select. But, most IP devices trim that noise out during their sampling which causes poor and erroneous comparator performance. Some comparators have limited compensation you can apply to improve performance, but it's not perfect.

That's why more systems are moving towards a full DMR solution with multiple sites connected through an IP backbone. Now you can land the system coverage where you want it, and where you need it. It's less expensive than a BDA and DAS when multiplied over many buildings. You get more features like trunking, private call, unit ID's, SMS, and GPS. From a system management point of view, you get to see who uses the system the most, you can allow or disallow activity, and it will notify you when a problem occurs. You can even push out changes in programming over the air with some systems so you don't have to chase every radio down.

I strongly suggest you pursue a DMR solution.