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Old 06-03-2014, 12:10 PM
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Default Building a repeater

Hello all, I'm not 100% sure that this is the right place for this but i figure you all would be the most knowledgeable about what i'm trying to do.

Here goes,

I am on a rural fire department that has a VERY hard time contacting our dispatch center via our portable radios, I have been tasked with building a repeater that we can mount in our command vehicle so we can talk portable to dispatch. We recently took a repeater out of service that was used for this when we went narrow band. We have a bunch of radios lying around to make one but i need a little help.
Here is what we have
3. TK-780's
2 TK-880's
1 MCS2000
1 CDM1550
1 PM1500
2 Maxtrac (we took these out of service due to narrowbanding)
1 Motorola RICK.
If we could use the maxtrac it would be as simple as reprogramming. I spoke with our local kenwood dealer and he said that they could make "something" but it would cost us. Also I know kenwoods aren't as powerful but we have an amp that we would put on the TX side to help it out.
I would really like to use the Kenwoods for both but if i could use the kenwoods for the input and the cdm for the output that would work too.

Any advise would be great
Thanks!!!
P.S. We do have an FCC license for a repeater.
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Old 06-03-2014, 12:16 PM
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Where I work, we use Motorola CDM1250's for repeaters often. And having that Motorola RICK, would make it easier if you can use the CDM1550 and another Motorola radio as the repeater kit.

Unless you are going to be able to stay wideband with the Maxtrac's, that is probably not a good option. Narrowband killed those off for us and we donated ours to the local ham/amateur radio community.

Is your department using trunking? The CDM1550 would be good for that as they have trunking. (Well CDM1550LS+ does, depending on when that 1550 was made and option.) I have not used a MCS series radio in a long time but that may be useful too.

An option is to find a local amateur radio club and ask them to make you a repeater using the radios you mention above, and for payment, maybe give them what they do not use for the project. Might be a way to solve your problem. Amateurs in my area are always whilling to help for some old surplus gear.
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Old 06-03-2014, 12:43 PM
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For commercial/public service use, the repeater or radios used to make the repeater must be type accepted for use as a repeater for that service. Many if not most radios do not meet this criteria.

The Maxtracs would not be useable simply because they do not comply with the new narrow band rules.
prcguy
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Old 06-03-2014, 12:55 PM
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Consider that mobiles have a low duty cycle and when placed into repeater operation may not be able to withstand the continuous duty cycle of commercial repeaters. You should however be able to re-use the duplexer (if equipped) from the old repeater. The RICK can be more difficult to interface if the radios aren't compatible with the RICK. The RICK doesn't have an identifier so users would need to be reminded of the public safety identification requirements. The repeater that was taken out of service was probably licensed for a fixed location, not portable It might be easier to build a mobile extender rather than a mobile repeater as well as get it licensed correctly.
BB
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Old 06-03-2014, 1:39 PM
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The repeater was taken out of a vehicle and I'm pretty sure it is licensed as a mobile repeater. I'm not too worried about the duty cycle because we would only use it once or twice at an incident. If we have a major incident the neighboring department has a rack repeater in their engine and we switch to that freq.
the way we had it set up before it could be used as an extender or repeater. Extender is more beneficial for us I just don't know too much about them


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Old 06-03-2014, 1:40 PM
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Our department doesn't use trunking. There was mention of us going to woscom but that was shot down due to costs. We are analog vhf


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Old 06-03-2014, 1:47 PM
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Maybe what you had was a "mobile extender". If that is the case you might only need to upgrade the non-narrowband radio(s) to narrowband. Also look at your license and see how the mobile repeater was licensed. Or tell us what the call sign is and many here will be able to help you interpret what you are licensed for. You might be able to get this up and going pretty easy.
BB
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Old 06-03-2014, 4:12 PM
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Quote:
Originally Posted by WA0CBW View Post
Maybe what you had was a "mobile extender". If that is the case you might only need to upgrade the non-narrowband radio(s) to narrowband. Also look at your license and see how the mobile repeater was licensed. Or tell us what the call sign is and many here will be able to help you interpret what you are licensed for. You might be able to get this up and going pretty easy.
BB
I took a look and it is licensed through the county as a "fixed location" repeater. So the person who moved it didn't update the license.
so i have a couple things to look at.
1. How much does it cost to get a license for our FD.
2. Since we are on a "county owned" system is there a certain type that we need? (We don't have one for our fire dept.)
3. Do we need one for an "extender."

I called our radio shop and they said it would be more of a headache than it is worth and we should just buy a 100w radio and call dispatch from our truck, however i tend to disagree. That defeats the purpose of a portable radio.
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Old 06-03-2014, 4:44 PM
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WA0CBW is correct. You should not just use mobile radios to make a repeater especially for commercial use. There is quite a bit involved in making a repeater out of mobile radios I have build several amateur repeaters using both Kenwood and Motorola Maxtracs. The Maxtracs I had to turn down the power to only 7 watts output because of the duty cycle plus I also put a fan on the TX radio to keep it cool.

Go here and read, read, and read some more: The Repeater Builder's Technical Information Page™
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Old 06-03-2014, 7:24 PM
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IMHO, a task like this should be configured by a radio shop. Even though it will cost money, it is something that needs to be installed professionally, or at the very minimum checked out by a shop before placing into service. Even though your portables have a hard time reaching dispatch, if its a simplex system and everyone is using the mobile repeater and it fails, then nobody hears any traffic at all. Just food for thought.
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Old 06-03-2014, 11:30 PM
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You do not mention if you intend to use a cross-band or in-band repeater. A cross band repeater would be from your regular VHF mobile to say a UHF radio. Technically much easier to implement in a vehicle, but the drawback is you'll have to scrape up some UHF portables to use the dang thing.

I suspect you want an in-band vehicle repeater to be able to use the handhelds you already have. Doable, but not for the faint of heart and requires at least the blessing of a qualified radio tech, let alone a full checkout to make sure the system works as advertised.

You say you have something that was pulled from service. What is this and what parts and pieces did this unit comprise of? Did it work for you before or did it have problems with it.

The things to consider on an in-band vehicle repeater are:

The extender frequency you intend to use. It needs to at a minimum of 2 mHz away from any frequency you
anticipate the regular mobile radio would use. 5 mHz or more is a lot better. If you do not have a frequency
you are licensed for that would fit, you'll have to apply for one. The rest of the county channels you have
would need no modification to the license.

You mentioned adding an amp to the extender radio. NO! Most vehicle repeaters run in the 0.5 to 2.0 watt
range. Your concern is how to crank a radio down to run that low. For on scene communications, 2 watts
is plenty.

You will require special filtering added to the antenna line to separate one radios transmit from the others
receive. Do not try and cheap out by omitting these, they are required. Also antenna placement on the
rig plays a big role in how well things will work.

I have installed my share of these, and always used ready made commercial gear from Pyramid Communications. If anything, check out their website before planning anything. They provide excellent information.

Pyramid's SVR - 200 - Pyramid Communications
http://www.pyramidcomm.com/storage/w...d%20Primer.pdf
In-Band Filters - Pyramid Communications
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Old 06-04-2014, 2:53 AM
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In my experience, the duty cycle of amatuer radio operators far exceeds any dispatch system. Some exceptions are the trunking control radio on Motorola systems and some paging systems. If dispatch systems were that keyed, then trunking would not work.

If the system is to be used only to contact dispatch, the mobiles should work. If it is a fire ground portable repeater, then the duty cycle will have to be estimated.

I was under the impression that the FCC only distinguishes between mobile and fixed stations. Fixed stations requiring a greater frequency stability.

Bob
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Last edited by rescuecomm; 06-04-2014 at 3:10 AM..
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Old 06-04-2014, 6:54 AM
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If you could give us the brand name and configuartion of the old repeater that would help, also what band or frequency the portables are on and the band or frequency Fire Dispatch is on. Using the a RICK you could take any narrowband capable radio and build a repeater. Since you havn't given more information I will try and help based on what is the most common fire scene scenario's.
Portables can't reach Fire Dispatch but hear it just fine, a Mobile repeater was originally built that takes the portables transmit on a different frequency and retransmits it at a higher power on the Fire Dispatch channel. This is a simple one way rebroadcast repeater also know as an extender, and it can be cross band or in band. This would entail using any radio narrow or not as a receiver(like a maxtrac), then rebroadcasting that receive frequency on a narrow-banded higher power radio(like a CDM)to Fire Dispatch. Since you have CDM mobiles I can assume you are not running 100 watts but at the most 40-50 watts, and I believe since you have had to narrow-band your equipment your not on Low Band since that band doesn't require it. This is the simplest way of accomplishing what you want to do, also the FCC type acceptance is for a mobile radio and you are running a mobile radio so no foul there.
The more complex way is that your portables are operating on the stand alone repeater that transmits to all units on the scene, and also transmits to Fire Dispatch. It is full duplex repeater that just happens to mounted in a vehicle, also doesn't require anything more than a radio type accepted for mobile use, and it also may be cross band or in band.
On an other note that has been brought up, mobiles don't lend themselves to more that 10-20% key up cycle. That may be the reason for the external amp you have. You can turn down the mobile's power and let the amp take the brunt of the work making the power you need.
My suggestion is to stay with Motorola radios since they are the easiest to configure to work with a RICK otherwise you have to cut wire and solder to pins or lands on non-Motorola equipment. Information on the RICK and it's many configurations is available on Batlabs.com.
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