800 MHZ and your experience with it?

[grnresqjeep]

Hey everyone,

Looking to hear peoples stories about 800 MHZ radio systems. I want to know the pro's and con's. I want to know the troubles you have had (if any) and the terrain type you cover (city,rural etc). Thank you.

[Medic2588]

Really depends where you're using it and what sort of infrastructure you have to support it.

I started out using an 800 system for urban dispatch. It honestly sucked. There were many spots in the city where there were dead zones and those were the kind of areas you really didn't want to lose radio communications. Many this was because of the lack of proper repeaters. As odd as this sounds, we were fortunate to have the main antenna destroyed when the South Tower of the WTC was hit on 9/11. It cost too much to replace, so they scrapped it and went to a UHF system.

Now I'm on a statewide project where we use an 800 system extensively. The State Police in NJ have an extensive network of repeaters so its almost crystal clear

Devin

[brentoli]

This is too much to ask for. Honestly.

There are too many variables in a radio system to go off of opinons. You need to have official technical data.

Our county LE uses an 800 LTR system. Its not set up right for what we need. Coverage is horrible on a WT, and tolerable most places on a mobile.

The state has the 800 SAFE-T system. It covers the whole county like a charm.

[scratrat]

The bad thing is if you don't have a signal, you're screwed. And hopefully not in trouble. The good thing is if it works, you can hear everyone so you're not stepping on anyone. I also found out (I don't know if this is just our particular system or what) that only a certain number of frequencies can be used at any given time. Like, even though fire, police, and EMS are on different channels, only 8 combined channels can be used at once. My radio will not work at all if I'm number 9. That means if 4 police officers are talking on different channels, and 4 firefighters are talking, I can't. I don't understand that since it's different channels.

We used it in NJ and it was pretty good because it was less urban where I worked. You could talk to one end of the county to the other, unlike VHF.

[brentoli]

When you key up the radio sends a burst on a control channel. It says who you are, what talk group you are using, and what permissions you have. The Main radio then takes that information and assigns a frequency for you to talk on. It also sends out a burst to the radios set to your talkgroup to tune in to that frequency. Everytime you listen or talk, it is potentially a diffrent frequency.

That is the benefit of a trunked radio system. You can run 20 talkgroups "channels" on 10 frequencies.

[Richard B the EMT]

In the early days of 800 MHz radio in NYC, on returning home from work, the liasion Lieutenant between the then NYC Health and Hospitals Corporation EMS and the New York State Volunteer Ambulance and Rescue Association suffered an injury on his back porch, tried to reach out on the new 800 MHz radio, and could not obtain a signal. He then tried reaching out on the older 400 MHz radio, and made contact without any problems, summoning help for himself (broken leg).

Using that as an example of a potential problem, there also was a movement within the department to limit usage of the 800 MHz units, as there was a fear, so far neither substantiated or denied, regarding possible radio radiation caused damage to woman's reproductive organs. Figure the antennas for the radios being on the hip of a "woman of child-bearing age" next to the womb, being the problem.

[brentoli]

[web:af9f8e61ee]http://wiki.radioreference.com/index.php/Trunking_Basics[/web:af9f8e61ee]

[Medic2588]

Ah, yea. What he said. Thank goodness there are people out there who understand how it works. I push the button and talk and occasionally it talks back.

Devin

[dahlio]

Here where I live, we use a GE/Ericckson/M/A com/Whatever system using EDACS on the 800 mhz band. We've been transitioning to new radio consoles/portables, thanks to Nextel and the 800mhz rebanding deal. It's programed in to the new radios that when we do change frequencies (which you can read more about here http://www.800ta.org/ ), all we do is turn a knob, and we're good to go (at least we hope so). They are, in my experience, very clear, and never have received interference, except when my pager is right next to it, but that has to do with Electro-Magnetic Pulse, not interference with other radio systems. Anyway, our system consists of Fire/LEO/EMS/Public Works/other township entities. In all honesty, public works only ever uses it in snow storms and stuff, and I've never heard any other town agencies talk. We have 6 repeaters at two repeater sites. Meaning 5 conversations, and one left over for the control channel. We have 40 or so talkgroups. Talkgroups are not channels, more of place markers. In other words, every radio has 6 frequencies programmed in it, but can only hear traffic on those talkgroups that are programmed, hence where the control channel plays a sorting role. Also, a feature with EDACS, is individual call, which can allow two radios to communicate with each other directly, without anyone else hearing. Also is the option to put it through a telephone system.

Overall, I think the system, at least for our township, works well, and very rarely does the system get maxed out. Only when it does, is when something big is going on, and that tends to involve almost every agency. If you have any other questions, post it, and I'll see if I can answer it. Good luck.

[Richard B the EMT]

Through my other than medical reading, if your radio gets hit with an Electro-Magnetic-Pulse, consider that radio "fried", as well as the ambulance's communications, computers, and the computer that helps run the engine of your car and ambulance.

EMPs, first discovered during "in atmosphere" H-Bomb testing in the Pacific, in, I think, 1963, burned out a lot of the "state of the art" (for 1963) electronics and electrical systems on the side of the state of Hawaii nearest to the bomb test site. This included overhead wires for both phone and power, street lights, house wiring, and the electronic medias.

Due to a ban signed in the UN, the US, which had signed on, could no longer do nuke testing in the air, which seems to be the only time the effects are observed, and not observed in underground testing.

Link to EMP at http://www.fas.org/nuke/intro/nuke/emp.htm . Link to EMP at http://www.fas.org/nuke/intro/nuke/emp.htm

In movies, the EMP has been depicted in "The Day After", "The Atomic Train," and "Godzilla 2000" (don't hold me to the year), where an experimental manned flying device is disabled by an EMP, which revives ol' Dragon Breath, only moments after the flying device had seemed to kayo him. Godzilla then drops a building on the craft.

Yeah, I know, I see a lot of movies.