Pro's and Con's of 800 mhz

[ICEMANTIM]

I know this is a little off the subject of the forum, but i am sure i will get good answers here. Our county is kicking around going to 800 mhz. The State (Ohio) is putting up a system that they say will cover the whole state. The people at the Fire Acad, get real defenceive about this when you start asking questions. I do not know much about Trucking. I know how it works, But do not know much else. What are the Por's and Con's of going this way. Also why can'nt you do it on VHF 150 mhz. Thanks Tim

[KG6EAQ]

I'm assuming you meant trunking not trucking . You can do it on VHF 150, if you can find the equipment. I've only seen a few trunking VHF radios, most were aftermarket boards for LTR systems. Most states that create a statewide 800mhz system, they usually offer access to local agencies for a fee/cost of equipment.

[FFCARTER46]

hi,

my county and some of our neighboring counties opperate on 800 mhz trunking. we have been on the system since 1996. we have never had a problem with it. with trunking you can have a wide selection of channels. police have about 10 channels, fire has about 30 channels(15 for vol. depts. 15 for city depts.) EMS about 6, PW has and school maintence have about 10, and the list goes on and on! this makes it very easy to communicate with other agencies with one radiosince all channels are available in each radio and very accesable! our county uses mts2000 type II! (full keypad and display) also if you have private call this allows you to call radio to radio with each radio having its own "telephone number" so your not using channels on the radio! we also carry telephone interconnesct on all our radios which allows us to make land line phone calls using the radio! we love the system and i highly suggest it!!!

[Josh]

hi,

my county and some of our neighboring counties opperate on 800 mhz trunking. we have been on the system since 1996. we have never had a problem with it. with trunking you can have a wide selection of channels. police have about 10 channels, fire has about 30 channels(15 for vol. depts. 15 for city depts.) EMS about 6, PW has and school maintence have about 10, and the list goes on and on! this makes it very easy to communicate with other agencies with one radiosince all channels are available in each radio and very accesable! our county uses mts2000 type II! (full keypad and display) also if you have private call this allows you to call radio to radio with each radio having its own "telephone number" so your not using channels on the radio! we also carry telephone interconnesct on all our radios which allows us to make land line phone calls using the radio! we love the system and i highly suggest it!!!

This is just one thing you can do with a trunking system that doesn't simply waste bandwidth, but it doesn't provide a "pro/con" about 800Mhz trunking.

I think 800Mhz sucks. Signals (in analog) break up a lot closer to the base stations than any other band. I can hardly monitor the county sheriff in my car without an external antenna on my HT because the signal is so broken up- and I'm in the heart of their coverage- less than 10 miles away from two separate simulcast towers.

800Mhz digital is another story, for me at least.

The MSP system scanning conventionall in the car (which is supposed to cover mobiles in 97% sucks on a portable in the car travelling in the 'fringe' areas as signals get really distorted and then don't come in at all.

However, the Downrier Mutual Aid system which covers the entire area I live, including 16 cities from 4 towers works great, especially from a portable. I haven't found any coverage holes except for inside of the mall where once, at radio shack, I got the dreaded beep and "out of range" display. Where the mall is located, there's a tower less than 2 miles away. This is not good.

That's about it. I've found that analog 800Mhz sucks, and that it cannot work without at least a repeater (simplex won't work at all) but 800Mhz digital is o.k., in most cases. It seems the biggest pet peeve I have is with all of the static received in the analog 800Mhz transmissions and having to hear through some low-modulation repeaters.

-Josh

[Pj]

Ok, I am going to try this again since I lost my first post...

I am really not a big fan of 800 unless the system is built really well, and that requires a ton of cash. The CSP spent $37,000,000 (before the CAD option) for a statewide Smartzone system with 98% coverage in most places.

Now, if you are in a fairly flat area, 800 isn't bad, as long as you have all the needed recieve sites, and a good transmitter. The boat is still out on trunked systems. If they are built well, they work (CSP, MASP, etc). However, if you do not provide the proper infrastructure, you have problems (DCFD, FDNY EMS). There were many times that FDNY EMS had problems getting out of buildings and they were getting "Out of range" and "busy" tones. This may have been corrected by know, but I do not know. If your 800 trunked system is not properly built, you can have some serious problems if you are in the PD or FD service. If you are in trouble and your radio can't access the system, your in trouble. At least on a conventional system in the simplex or talkaround mode, you have a shot of someone hearing you.

Trunked systems make excellent use of specturm, but if multiple agencies are going to be involved, make sure everyone can afford it and use the same setup's. Some can afford more than others, which can present a problem. We have some county fire dispatch systems that use just a few low band channels but run over 20 depts without too much of a problem.

As for range:
800MHz requries a more receive sites then the others. Lower power radios at the higher freq's. Not good for wide open rual area's, and even some spread out suburban area's.

UHF - Typically good for suburban/city scenes depeding on the terrian. Required less voter sites (typically) and if used in a conventional system, you can use other vendor equipment unless using DVP etc. You can also use higher powered radios.

VHF-HI - Good for surbuburan/rurual and even upto city area's. Great range and does well with hills/valleys. Portable antenna's tend to be a little longer and you can xmit about another 1watt on the portables and mobile can go upto 110watts if needed. Problem with VHF is more chances of "skip" interfearence. In my former town, we had (at the time) three receive sites and one transmitter. System worked pretty well from the river area and up over the mountain to the other side of town. The town had a pretty deverse profile, but it worked well.

VHF-Lo - Extreme long distance, but in not great for FD/PD services. Portables will have the large antenna's and will be clumsy unless you are using VRS's, which add more cost to the overall system. Repeaters are about non-existant. Most lowband radio's around today tend to be high powered, but you can get lower powered ones. Long range skip can be a problem. (I can hear the CHP on the local MSP channel, and I get Florida Metro Dade in the summer on our county fire channel during the summer like both were next door).

[gws]

The Ohio MARCS system ( http://www.ohio.gov/das/dcs/marcs/AboutMARCS.htm ) is indead a state wide system. Its an apco25 system. Your county should already have at least one radio at the dispatch center already for interservice communications. MARCS would have paid for this. These are somtimes linked to local freq sometimes just a seperate radio that the dispatchers can pass traffice from local nets to MARCS. MARCS was designed as a state system, not a public service system. It links many state agencies.

Coverage is going to be a BIG DEPENDS, I dont like the audio of a digital system.. Hey do you know what the most common words on a digital system are? "Can you hear me".... -:)

Depending on your the size of your agency you may find its not cost effective. Apco25 radio's are NOT cheap!!!! Then if you do get on you have air time charges.

I know our small volunteer fire/ems had to go to city council 4 times just to get a stinking $300. I wounder how long its going to take for a $5000 unit.

[fireradio]

Coverage is going to be a BIG DEPENDS, I dont like the audio of a digital system.. Hey do you know what the most common words on a digital system are? "Can you hear me".... -

I am a frequent user of the digital trunked system in my county. The system is county-wide, and covers more than 399 square miles (255,360 acres). We have eight sites, and coverage is really quite good. The same as, if not better than, many neighboring counties' analog systems. I very very very rarely have to say "Can you hear me..." I can even work my way pretty far into neighboring jurisdictions and still be able to use my (portable) radio. We're adding 3 more sites in the very near future to make the system even better.

It all depends on how the system is designed -- if it is designed well, digital is WAY better than analog. If it is designed poorly, it will suck, just like a poorly designed analog system would. Thanks to digital, I never have to hear annoying, fluttery static and the like. If you're going to go 800, I personally recommend digital.

[RKG]

The original post merged two very separate issues: 800 mHz and trunking. They are not the same.

800 mHz is just another slice of spectrum. It was selected for trunking applications because trunking applications need a comparatively large number of channels and it needs them on a "clear channel" (i.e., no nearby co-channel users) basis. Since 800 was new, it was available to make a more organized (more or less) allocation than could have been done using VHF, UHF or Subpart L bands.

Because 800 is twice as high as 450 (which is three times as high as 150), it suffers from those attributes that are affected as frequency goes up. It handles foliation poorly, and for some reason it does not multipath as well as UHF. This makes the ability to get in-building coverage without the use of in-building equipment more difficult. Overall and as a general matter (that is to say, subject to specific case exceptions), it is harder and more expensive to get the same areal coverage at 800 mHz than it would be at a lower segment of the spectrum.

Trunking is a system for allocating a specific repeater pair on the basis of need, rather than arbitrarily. In essence, a handful of physical "channels" can be made to function as several dozen "logical" "channels," much the same way as a few lines from the Phone Co. to a building (known as "trunk" lines; hence the name) can serve several hundred in-building extensions. In a phone system, the management of the lines is handled by the switchboard or PBX; in a trunked radio system, it is handled by the exchange of inbound and outbound service words and a system controller.

In Massachusetts, the statewide trunking system consists of 28 800 mHz frequency pairs, but it provides the functionality of over 200 "channels" to over 4,000 authorized users (counting a cruiser and a portable as two units).

From a spectrum management perspective, trunking has a lot of advantages over conventional "fixed channel" assignments. From an operational perspective, it has two limitations of concern.

The first is: what happens if the trunking system fails (as it will from time to time)? The solutions are "zone trunking," "site trunking," and "FailSoft," depending on system configuration. These techniques handle some of the problems but not all. Like everything that is more complicated than its alternatives, there are a host of failure modes.

The second operational problem is the lack of "direct." At a fireground, a jake caught in a tough situation inside a burning building (or the second sub-basement) can talk to the other companies out on the street, even though he cannot make the repeater, by switching to "direct." Since he is transmitting on the same frequency that the companies on the street are listening to, no action by the outside companies is required. "Direct" has saved a number of firefighter lives, and is now required by NFPA standards for fireground use, which means that trunked radio systems have to have one or more "conventional" channels for fireground use. (A very effective employment of this strategy occurs in the City of Cambridge, Massachusetts.)

Similar concerns affect police and other public safety applications, though not as -- pardon the expression -- directly.

A well-designed and well-implemented trunked system will cost a lot of money. However, it can yield a functionality that, if achievable at all by "conventional" means, would cost even more. Its limitations must be understood by the system designer as well as by the system user, and some accommodation of critical functions must be made.

[RADIOMAN2002]

My experience with 800 is that it doesn't work in the woods. At least not without a lot of transmitters and voters. I would like to see more 150 and 406 and 450 trunking systems. The coverage would be better with less cost. BTW New York State has gone 700 mhz to stay away from Nexthel, but the range issue is still the same.

[RadioSouth]

800 MHz seems to be a resonant freq. with pine needles. Many pines
in the area ? If so, RF will absorb into them when they're wet. In my opinion 800 is very oversold, not desireable other than is a clear spill over
area from loaded VHF and UHF spectrum. 800 trunking needs significant infrastructure to make it work properly. I'd rather see narrow band VHF and UHF utilized to offer the needed spectrum. 800 doesn't do anything well, it's only the trunking technology that got attached to it that made it go anywhere.

[ICEMANTIM]

Thanks for the great feedback. Yes i meant trunking not trucking Sometime my spelling can be a little off. I am fairly sure the system is 800 trunking digital. I am in Shelby county Ohio. The county to south Maimi has switched over to some kind of 800 system not sure what kind. I know they have had many probelms with get into and out of biuldings. (they still page out on 150 mhz). Our fire department has $130,000 budget and covers roughly 100 square miles. Some smaller fire departments have to get by with onlyt $15,000 a year. This would make it very hard to get radios. We have 12 portables and 8 mobels. This still would be a large dent in our budget. Thanks again for the great feedback. This maybe an other posting. Why do the people at the State level get very defenceive when you question them about this. We had a person here at our fire department doing training and he started talking about how great the new system was. When i ask him about the problems other where have he got mad and moved on!

[Pj]

Prodjects like these tend to get very personal. Lately I have been fired up with one of the bosses on how to program the MDC ID's in the new radio's.

Also, some people become very attached to a sales pitch, and when promises don't come through, people tend to get irate and don't want to talk about their shortcomings on not following though... just my observation.