1. #1
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    Question Radio dead spots

    We have one building in particular (a hospital) that we make lots of automatic alarm calls to, where it is impossible to communicate with handheld radios (around 154 mHz). Once you walk in the door you can't use T/A, much less key the repeater.

    I'm wondering what strategies other departments use in buildings that are radio "dead spots".
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    What kind of infrastructure is the rest of your radio system now? I'm guessing by the fact that you mentioned a Talkaround option, that it is a repeater of some kind. Is it a voting repeater with multiple reciever sites? Can you hear the repeater and the repeater just can't hear you? If so, you can add another remote reciever inside the hospital This will probably take care of the repeater hearing you. It works very well here.

    If you can't even hear the repeater from inside the hospital, that is going to be a little more complicated to correct. A passive repeater with a bi-directional amplifier is an option depending on how big the building is. A whole seperate simplex operating channel with an in-building extender/repeater is also an option. Relocating the trasmitter is of course and option but probably not practical.
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    It must be something with 154 and hospitals...Because we have the same problem. What we do is have everyone go to our fireground channel (can't remember the freq) and we have one person out side designated as Comms. He has 2 radios one on fireground and one on our primary. That is about the only way we have found. Even with that their are dead spots but its better than nothing.
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    It is not just 154. It is the VHF High Band all together. Low band (46.xx) would be even worse. These frequencies have very poor building penetration properties. To put in a simple way, they tend to hit walls and stop instead of finding a way out like UHF (450/460) and 800 do. A regular wood framed home is not usually a MAJOR obstacle. But you go inside a steel and concrete monster like a hospital, forget it. You might as well drag a string with tin cans along with you.
    Last edited by nmfire; 12-11-2003 at 08:24 AM.
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    We have a few areas that we can't transmit from on our normal or on the repeater...so we are looking at a system for our trucks to take our transmission and "juice" it up a little and hit the repeater from their.

    This came around due to a situation with a rollover into a creek and I was trying to get more help assigned...but no one heard me. I had a deputy contact the County Sheriffs dispatch to relay info. They have the system above.
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    Your refering to vehicle repeaters. They recieve your low power portable radio on one channel and rebroadcast it on the high power truck radio tuned to the disatch channel. These have their ups and their downs. When they work, they are convinient. When they don't work, it becomes RF Hell. They also will NOT help anything if:

    1. The portable can't reach the truck to begin with. It sounds like this is the case in the hospital since he said T/A won't work either.

    2. The truck is out of range of the base as well.

    3. The users are not properly trained in their use. It is very easy to make things even worse.

    4. The truck and/or truck radio isn't working or malfunctions.

    In order to make a vehicle repeater system work here, they would need to buy all new UHF portable radios along with the $1,000 vehicle repeater for each piece of apparatus which is probably not going to be feasible for one building.
    Last edited by nmfire; 12-11-2003 at 08:32 AM.
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    Their has been talk about going UHF around here forever...but since everyone in the County has to agree. Nope...they still can't agree the sky is blue.

    It all comes down to the little volunteer departments don't have the money or the use of going to UHF. And since we have a county wide dispatch....we are stuck. We want to go to the OHIO MARCS system....but at $1500 a portable...thats not going to happen.
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    Talking Re: Radio dead spots

    Originally posted by ullrichk


    I'm wondering what strategies other departments use in buildings that are radio "dead spots".

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    Originally posted by nmfire
    What kind of infrastructure is the rest of your radio system now? Can you hear the repeater and the repeater just can't hear you?
    If you can't even hear the repeater from inside the hospital, that is going to be a little more complicated to correct. A passive repeater with a bi-directional amplifier is an option depending on how big the building is. A whole seperate simplex operating channel with an in-building extender/repeater is also an option. Relocating the trasmitter is of course and option but probably not practical.

    One repeater covers our entire jurisdiction. We are unable to hear or key the repeater from inside the building. T/A works a little better than line-of-sight inside.

    I'm not a radio guru - can you give me the Reader's Digest version of the difference between our repeater and a passive repeater? How about the extender/repeater?

    How much would we have to worry about interference with the hospital's telemetry?

    The building itself is 3 stories, mostly reinforced concrete with a recent addition being steel frame with a glass curtain wall. Come to think of it, the glass has a mirrored finish. Could that be shielding our signals?

    Thanks all for the input. In the meantime, I guess we'll be going with the tin can and strings.
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    Oye veh. This could be a tough one if you can't even hear the repeater in the building. Remember what is inside reinforced concrete... STEEL! Lots of RF blocking grounded STEEL. Metalic Coated glass is also a big time killer of RF penetration. Bascily, this building is an RF Black Hole. Sigh.

    A passive repeater works like this.

    High gain directional antenna on the roof pointed at the repeater site. Another antenna inside the building. Coax connecting the two antennas together with an RF amplifier in the middle. It is kind of like a funnel that takes the RF that is outside and brings it inside, and takes the RF inside and puts it outside. How close is the hospital to the repeater site?? The closer it is, the more RF there is being shoved into it and the less it needs being pumped out to reach it. If it is very far away, it might be an exersise in futility. Since it isn't spedific to one frequency, it will amplify anything that is there, repeater, talkaround, or other channels within the band. How well does the talk-around work within the building, like talking from the first floor to the third floor inside??

    The extender repeater is very similar except it is frequency dependant and uses another small repeater. You would need to add another channel to your portables that would only be for operating inside the hospital. This is where you get creative. You can make a repeater out of two mobile radios connected together with an extender module. You have one radio set to the main fire repeater channel and hooked to an antenna on the roof of the hospital. The other radio is tuned to your new operations channel with an antenna in the building.

    What you say on the new operations channel inside is recieved by our "hospial repeater" and rebroadcast on the main repeater channel at the same time. Anything on the main repeater channel (which also includes TA traffic outside) would get recieved by the "hospital repeater" and rebroadcast on the new operations channel.

    Does that make sense (I hope)? The extender would be far more reliable than the passive model. Frankly, it wouldn't cost a lot more if you make it out of some used mobiles radios that are in vast supply very cheap and still reliable. Motorola MaxTracs and GM300's are great for this. The module that connects them together is rediculiously simple and can be bought or made very cheap. I can give you some names to contact for them if you would like. The other thing is obviously the hospital would have to OK all of this.
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    Default Radio Dead Spots

    nmfire

    To put in a simple way, they tend to hit walls and stop instead of finding a way out like UHF (450/460) and 800 do.
    Our county went to an E.F.Johnson 800 mHz system about 10 years ago and E.F.Johnson tested throughout the entire county for dead spots as a selling point of the system. Their findings indicated less than 4 or 5 % of the county had these dead areas (mostly on fringe areas). The county has found a larger number of dead spots including inside many buildings that were never tested.
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    You can use multiple repeaters if you like.

    Change the input PL for the repeater as you like. In Cali CDF has as 6-8 repeaters on different moutain tops. You just program the same freq with differnt PL on the input. Talk from what ever mountain top is the closest. Not a big deal if on a mobile. Makes a big diffence if you are down in a hole on a portable.

    Go to www.sunwize.com and get a solar ready system, repeater(motorola, Kenwood, etc..) duplexer(telewave, emr,etc...) and anttena(sinclair, andrew etc...) Put on the roof and any other tall place around town that you have problems.

    I have some other solutions. This works on the KISS principle.

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    You could put up another seperate and closer main repeater. However, that is not going to work if there is no decent spot to put it. It's coverage will be vastly different than the existing one so you may not reach mutual aid and other incoming units and they may not reach it. You'd then also need to lease lines or microwave back to dispach, have another line added to the radio console, etc etc. You also would need to license that second repeater with the FCC as an FB2S wich would require coordination, coordination fees (lots of $$), and several months worth of paperwork and waiting. Then they may or may not approve it.
    Last edited by nmfire; 12-12-2003 at 06:12 AM.
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    Got it, nmfire!

    I think I'll suggest the extender to the powers that be. We happen to have a "spare" frequency that would work in this app.

    I'm guessing that the extender idea could be used in several buildings without fear of interfering with each other (RF shielding was the problem to begin with, right?)

    FWIW, our repeater isn't exactly close to the hospital, but it has the advantage of elevation. It has good line of sight well beyond the borders of our jurisdiction. We haven't found any dead spots outside of buildings in our area. I happen to know how bad the hospital is because we go there a lot.
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    Default could you...

    connect 2 radios together. Put 1 on TA and the other on your main frequency as someone else suggested. Have the cable between the 2 be something like 10 feet and put the whole thing in a bag. When the entry teams go in they go to TA on their portables and drop the bag @ the door. Put the TA radio inside the structure and drop the other outside the door. Assuming that you can transmit from the farthest point in the building to the lobby then you should be able to get outside via the bag. This would also make the setup portable so that you can use it in other buildings such as warehouses etc. If you have another channel you may want to use that instead of TA.

    Thoughts?

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    Chances are you can do the same thing in another building with the same frequency. It sounds like this hospital is a pretty good RF shield. If you can barely use talk-around from standing outside to standing inside, you probably won't have any problems with a building several blocks away.
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    Whatever you decide upon to solve your communications problem...keep this in mind...you might be able to get the hospital to pay for it. When the hospital did, does, is doing, major renovations, that would be the opportunity to get upgrades done in the building to improve radio coverage for public safety. The local police may be on the same radio band, and would benefit from this also (so you could force the issue from two sides). Whether you install a repeater, bi-directional antenna, or whatever, the hospital might be able to factor the cost in with the renovation (just like upgrading a fire alarm system or sprinklering a building). The first method might be to have the chief ask, as part of the fire department's planning approval. The second, would be to pass a community by-law that requires adequate radio coverage in all large buildings (you decide what adequate means). Let's say someone is building a large commercial warehouse in town. The by-law would require them to add whatever is needed to the structure so that your radios worked inside. This may involve a lot of work, or none at all, depending on how well your current radio system works.

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    I must have missed it, but to address Skwerl530's idea:

    This will not work. The radios will de-sense eachother and you get nothing on either end. Also, it isn't quite as simple as "just wire the two together and drop them inside and outside. It takes a little more technical engineering than that.
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    Lightbulb

    Perhaps grabbing one of security's radios upon entry, with a security liason at the IC, as the hospital already probably has some type of intrinsically safe reliable communications system inhouse. Where does the IC set up? Maybe relocating them to a more central location could provide some level of comms. Anything you do on your own is going to be big bucks. I like the idea of having the hospital put in the amplified passive antenna system, but depending on the size and layout of the place, it would be an engineering nightmare trying to work around not only steel, but, also any of the other shielded walls providing protection from x-rays, and the like.

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    Relying on another agency's radio system, if one even exists? I don't know about you but I wouldn't be "grabbing one of security's radios" if the building was burning. If I needed to call for help in a pinch, I am not using a radio I "grabbed from security."
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    Command location doesn't seem to help with radio reception, so command is always right outside the main entrance. The alarm panel and printout is right there, as is the information desk, PA system, and elevator. The maintenance shop is just a few yards down the hall.

    In an ideal world we would pass the responsibility to the building owner, but since we're discussing going to 800 mHz trunked in about five years, it really wouldn't be right to stick it to them twice. (We have no idea yet how well 800 will work in this building, but it can't be any worse!)

    I'd also be reluctant to "borrow" someone elses equipment in an emergency situation.

    I'm still going for the repeater/extender idea, but it's hard to get all the powers that be together this time of year.

    Thanks everyone for the input.
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    Originally posted by ullrichk
    ....but since we're discussing going to 800 mHz trunked in about five years, it really wouldn't be right to stick it to them twice. (We have no idea yet how well 800 will work in this building, but it can't be any worse!
    Oh lord have mercy. Lets hope that in five years, the people who build (and fund) these systems cure their rectal-cranial inversion. The mentality today is....

    "OK, so this design will give us seamless coverage. Great, so what can we cut off here and there to save a few bucks?? We don't NEED this site, we don't need that reciever. This will cover most of the town which is just as good as all of it."

    If they put the trunking site in the same place your VHF one is, the trunking system probably won't penetrate the building either. However, an 800Mhz simplex / talk-around channel might just find it's way out of the building where the VHF wouldn't.

    Keep in mind that even if the actual trunking system covers into the building, you NEVER use a trunking talkgroup for fire operations. You would use a simplex channel like you do now.
    Even the burger-flippers at McDonald's probably have some McWackers.

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