Crossbanding Info Request

[Alex663]

A local Fire Department is interested in Cross Banding and I have a couple questions I need answered. First, some background info: They are currently on VHF (~153 mHz) and deal with other FD and EMS agencies on UHF (~455 mHz) on a daily basis. Until now they have a couple UHF portables that get moved between trucks and you hope to have the radio at the right time. I was asked about Dual band portables and advised against it, but have thought about cross banding. They would like certain trucks that are commonly summoned to deal with UHF agencies to be outfitted with a crossband setup. My thoughts were 2 CDM 750/1250's (1 UHF, 1VHF), and any other associated hardware, a RICK is the only thing I can thing of. It would be easiest to use 2 seperate antennas mounted on the cab (i think) so no need for a duplexer. They want to keep it simple.... Add 1 channel to their portables labled XBAND (or similar), go to that channel, have the truck operator select the correct agency on the UHF radio, and then get to putting out fires.

Here are my questions.....
1) Is this easily do able?
2) What type of cordination will be required with the FCC?
3)Am I thinking of all the neccesary equipment?
2 Radios, 2 Antennas, 1 RICK, and misc wires
4)Will the radios need a fan system to cool them?
The radio will be used at a low power output, because this will be for on-scene comm's.....not trying to talk across the county.

Any thoughts are welcome!

Alex


PS. Anyone have a preference on RICK's? Model #'s welcome....
PSS. any experience with this.....
http://cgi.ebay.com/RA-2-Repeater-Adapt ... dZViewItem

[rrfd43]

I have one of those repeaters from e-bay. It works good between a vhf maxtrac 45 watt and a uf cdm1550. I crossband ham freq's and need to keep a fan on them. A little "tweeking" was necessary with the audio. Decide for yourself though if the simple solution is ok for life-safety situations you encounter. I can't help you with the licencing requirements, I'm sure someone else will chime in. You can also contact your local frequency coordinators.

The guy who makes that interface is a memeber here. Send him a message looking to deal through batlabs. He was great to work with, fast shipping, and immediate support.

[Jim202]

My first question is how many vehicles are you talking
about doing this "CROSS BAND" linking to? If you do it
to more than one, how are you going to prevent more
than one of these devices from being active at any
point in time?

The vehicle repeaters from several companies have
circuitry that sends a signal out every time they are
turned on. If there is another VR being used, it will
be shut off with the arrival of the new unit.

Second, you need to look at the cost of this cross
band system. You can almost put a second radio
into the vehicles for what it will cost for the CBR system.

The third problem you will run into is the FCC license
issues. Depending on how you do it, your probably
going to cause a license change to be filed. This will
also probably cause this issue to be run through a
frequency coordinator. That will cost some place on
the order of $200 per frequency per location. A
system license is much lower in cost depending on
how you word it all.

Jim

[Alex663]

Jim, We are thinking 1-3 trucks (an engine, a ladder, and a rescue). Typically only one of those trucks at a time will leave the district, and even if we did have multiple trucks on scene I am aware that only 1 system should be on at a time. Really the only time it would be turned on is when they are operating with a different agency, which happens maybe once a week.

2nd, simply adding a mobile radio to the truck wouldn't accomplish what we are looking to do. As it stands we have a couple portables on UHF to communicate, but at working fire we may have 30+ firefighter and not enough portables to distribute to them all. So the purpose of the cross band was so the guys could use the current radios which everyone has been issued to communicate through the Xband repeater to the firefighters on UHF

Is it not possible to just change the current license type? The intentions of the system is not to talk long distances, it is simply to communicate on the fireground. In all reality the power output could be limited to 4-5 watts. Im wondering why the FCC would have too much of an issue because we can talk on either UHF or VHF channels for emergency purposes, so the repearter would almost be unnoticeable. Im not trying to get under the radar here, just expressing how I see it from my perspective. Low power output on channels we already have a license/authorization to use, and limited use. Am I out of line there?


RRFD43: I was thinking sometimes a simple solutions provides the most reliability. Without a RICK the system would accomplish the same thing and have less piece of equipment to go bad, but that is also why I'm asking around here for advice

[Will]

This could work for your application, only need one added, UHF, radio.

http://www.c-cor.org/echocomm/Extmdl.htm

[kb0nly]

If your going to put in a UHF radio anyway.. Why not just have two mobiles in each unit so you can be on either band as necessary.

[Alex663]

I guess i'm not making myself clear.... We currently can talk on UHF, but only the firefighters who have a UHF portable can (about 1-2 per shift). On a fire scene you may have 20-30 units who do not have UHF radios. Now, not all of them need to talk at the same time or at all, however, at times all do need to hear orders over the air. Putting a mobile UHF by itself in the trucks will gain us nothing, we need the firefighters with VHF portables to be able to listen and talk to firefighters in the floor above them who have UHF portables. Now, have I clearified this enough?

[kb0nly]

Ahhh, ok. I thought that's where you were headed with this but i just wanted to double check.

Than it wouldn't be a bad idea to put a crossband setup in a vehicle, however, if you put crossband capability in more than one vehicle make sure only one gets turned on at a time, this is where you can run into troubles.

That's why they used to use Pac-RT/PL's for stuff like that, so they could all coordinate with each other. The problem i see you having is that you still need a UHF mobile with crossband capability in each vehicle being used otherwise you can never guarantee having one on scene. That is unless you have one vehicle that is guaranteed to ALWAYS be on scene when it might be needed.

It's too bad your on VHF and everyone else is on UHF, makes it hard to cooperate that way. What brilliant person is responsible for that? The other problem comes in range, i don't know what your area is like and what kinds of situations you might come across, but if the truck with the crossband setup is at ground level, obviously, and you got guys high up on UHF, they have to reach that mobile to in turn reach the guys on VHF only a floor down in your example. Seems to me in an emergency situation like that i wouldn't want guys putting their life in the hands of a crossband repeater. You also have to remember, if the guys on VHF are chatting constantly then the UHF frequency is also tied up for the guys with UHF HTs, and vice versa. Its a one person at a time system, also, the person talking on UHF has to be aware that the person on VHF can't reply right away unless the UHF side goes quiet long enough for it to go the other way.

I hear that problem all the time, one of the local power utilities had both bands a couple years ago, and they had extenders in the trucks that they would turn on when going up in the bucket truck, etc.. The problem was always that they would be jabbering on UHF and the dispatch couldn't get a word in edgewise on VHF.

I still think your best bet, when possibly lives are at stake, is to get everyone portable on the same band. However, i realize that your guys still need VHF to talk to their trucks and so on, and the other guys need UHF for their comms, so about the only way to fix it is to either put some VHF's in the hands of the other guys, which doesn't guarantee they will be around when needed such as you have discovered with some of your guys having UHF, or you need some dual band handhelds. Of which i don't think there is any available as far as Motorola, as for other brands i don't know if they have a commercial grade dual band version. Yaesu/Vertex makes nice ham band dual's, but i don't know if they make a commercial version also.

All around tough one to answer.

If you go with mobiles crossbanded, remember, train everyone in their use. But also remember if your chatting away on VHF your also blocking the guys on UHF from getting a word in.

[firemanfox]

my $.02 sense I deal with this on a semi regular basis right now. Our county switched to UHF the neighboring county is still in the 46.xx range, so when going mutual aid it's tough to "play together". Normally what goes on is the commanding officer had both portable and relays messages back and forth (very inefficient). I have thought about making a crossband repeater but we only go to the other county maybe once a month at the most. I would have to say though that the firefighters aren't putting all their eggs in one basket if they are using the cross band. The uhf guys will still be able to call other uhf guys and the vhf likewise. If the worst case scenerio the repeater goes down they are at worst back to where they are today. If you can have a command post with both uhf and vhf radios to make sure each side will still be heard if something goes wrong with the repeater, I'd say you have taken the risk out of the system. Anyway that's just how I see the risk involved maybe I missed something though

[n9upc]

I understand what you are trying to preform and what your end result should be or should I say what you want it to be which is:

Have the ability to use a VHF radio to talk over to UHF!

Now as to what you have listed is feasible and seems to be a good solution but as others have said remember a few things:

1.) Being bi-directional can cause some issues such as someone yaking on VHF ties up VHF and UHF, and vice a versa.

2.) Do not cheap out on equipment as we are talking about PS apps (I am not saying you are I am just saying please do not.)

3.) Cose effective ness may turn into somewhat of a serious issue as now you are buying from what it looks like another 3 UHF mobiles plus a RICK unit for each and thus can get very expensive.



Here is how we did apply a solution to somewhat of the same problem you are having here.

- At first we started out by having dispatch do a temp patch through there console between our VHF Tac channel and the 800 Mhz talkgroup. This was good for awhile but then some dispatchers had problems with either leaving up the patch or accidentally cross patching more channels/talkgroups then what should have been.

- So the next solution was to try and do portables like you listed. This was somewhat of an ok solution except that it was a little difficult on the on-scene ICS communication person especially when someone was trying to talk to someone on an 800Mhz talkgroup.

- The next part we went with was then going and making an automatic crosspatch off of the radio tower on a Tac that was now only used for crossing over to 800Mhz and that is all. However, if you had trouble hitting the tower then you were kind of screwed on VHF.

- So our final solution was to make the crossband set-up 100% portable. We bought a pelican case mounted the radios in the case and then have it so that the first unit out grabs the case and then it gets set-up upon arrival. Therefore, we do not have to outfit every vehicle and our fly vehicle can even take it out for usage.


Therefore, I would suggest a fully portable set-up and just send it out on any mutual aid requests. I can for see a problem with units rolling up on scene and having to many repeaters on at once causing interference.

Whatever it is good luck and I hope you find the solution to your needs.

[twowaytekk]

You may want to look at the Pyramid vehicular repeaters. They work great and you won't have to worry about having more than one on scene. If all you are looking at is fireground comms then the 2 watts they output should be more than enough power.

BTW...there are a tone of UHF 25 KHZ units on ebay right now....

Mark