repeater first time setup questions

[mm]

No those mobiles do not meet the stability requirement for repeater service and they are not legal power wise either, so they are not what you want to use even for a short term interim setup.

This is not ham radio where you are legal to design and build your own repeaters out of any type of radio you can cobble together, in the commercial service you need to use repeater equipment meeting the correct stability, power and modulation of your license, you also are required to use a specific antenna height, AAT, and antenna gain, dBi, to meet your coverage contours, too little coverage is just as bad as excessive coverage and both bring similar FCC fines

The FCC has been levying fines for simple infractions such as the Co-ordinates on licenses being wrong by even a few tenths of a degree, antenna height not meeting the licensed height on your license, antenna gain being incorrect, radio coverage that does not meet the license and numerous other things that you would not think would bring enforcement action.

Fines for improper repeater site builds are one of the biggest sources of FCC revenue.

Have you thought about how you are going to confirm that your site is meeting an environmental impact study and the required MPE guidelines in reference to proper postings that are required on your equipment ?

If your not aware what these are then I'd stop right now and get some professional help and if your professional help doesn't address any of the issues that I mentioned then I'd seriously look somewhere else for guidance.

With the government looking for money anywhere and anyplace, the FCC isn't blinking twice about giving out big fines to public safety and any other licensed agencies who stray.

I wouldn't even attempt a repeater these days unless every i is dotted correctly and every t is properly crossed, you want everything meeting the license 100% correct otherwise the fines are not worth it and yes the FCC has no sympathy even if you are a little VFD with no money to burn, they will and are passing out big fines these days to anyone who messes up.


Mike


You will not be able to pick any desired gain antenna either, your antenna gain will depend on your licensed contour coverage and the height above the average terrain, all this is on your FCC license so you need to do a coverage analysis in relation to your antenna height on the tower and then pick your antenna which will also require knowing your licensed transmitter power.

It's not as simple as picking an antenna, choosing any location on the tower and then adjusting your repeater power, everything needs to match the FCC license, otherwise ?

 

[giguchan]

Well said!
you are correct about the GOVT fining anyone they can just to get some Revenue, I am in the Cellular business.. The Govt has us and anyone who can be fined for anything. in their sights. Some are very silly silly things too...
Thats the Govt for you.

 

[mmckenna]

Wait a second....

I don't think I've ever posted here before, only lurked from time to time, but this thread drove me to actually sign in and post...

MM is correct, you can't just put up whatever you want. You license will dictate what you can do. When you license for these frequencies, it will be done by location. Your license should show a location for the repeater. That will have a bunch of information tied to it regarding the antenna height, the power output, the ERP as well as the frequencies. There should be a second location field that will be for your mobiles, it will usually show something like "25.0 km radius around fixed location 1". That will cover how far you radios are allowed to function around your repeater. Outside that area, you are not licensed to operate.

Case in point, for a police system I run: (location data changed for privacy)
Loc.1 XXX Building, 123 Elm. St. City: Bobville County: Podunkville State: CA
Lat.(NAD83) 50-50-49.9N Long (NAD83) 120-00-00.1W ASR NO.:XX Ground Elev 237.0
Loc. 2 Area of operation
Operating within a 25.0km radius around fixed location 1

So, the license dictates exactly where your repeater can go on Location 1. Your mobiles/hand helds are licensed to operate in a certain radius of your repeater.

Based off that info, you could then design your system. Highest gain antenna and highest power output isn't up to you, it's up to the license. So, you need to tell us what your license allows you in ERP. You can then design your system by choosing a feed line and antenna to keep your ERP within your allowed levels.

Also, based on your location 2, or whatever is listed for your hand held and/or mobile stations, you can figure the rest. Since you are in the flat lands and on a very high structure for your area, you need to figure in your antenna gain and down tilt. No point in going with a high gain antenna and blasting all your power at the horizon if that isn't where your mobiles are allowed to work. Also, running high gain antennas from a tall building with a tall tower on top can actually cause some coverage issues close in around your tower. Using lower gain antennas with some down tilt will help that.

Issue 1:
I'd strongly recommend you do NOT use a repeater for your fire ground. Use simplex. If a fire fighters life depends on his radio, depending on a repeater that could be a long ways away isn't the way to do it. Fire Ground should be simplex, radio to radio for simplicity and most reliable service. You could use the repeater output in a talk around mode for fire ground and the repeater for "business use", you just need to make sure your radio users understand how to use the two options.

Issue 2:
Designing your system. A high tower on a high building is great, if you license allows you to use that. You need to let us know where your equipment is going in relation to the tower. Is it in a room near the base, or farther away, like down inside the building? Your coaxial cable run length will tell us a lot. Using the coaxial run length along with your allowed ERP would let us make some calculations on your feed line losses, antenna gain and come up with something that will work within the constraints of your license.

Issue 3:
Your radio system is ONLY as good as your antenna system. Installing an antenna and coaxial cable on a tower is time consuming and expensive. Best do it right the first time. 1/2" heliax would be the MINIMUM I would recommend. For runs like you are talking about, 7/8" heliax would be better. Remember, it's not just how much power your repeater is cranking out, but how well your repeater can "hear" the hand held and mobile radios. Picking an antenna based on the power you should see at the top end of the coax would be the next step. Likely, a lower gain antenna , maybe 6 or even 3 db with a bit of down tilt, would be the right path, but all that would depend on what your license says.

You may have limited time to do this. Often the FCC will require you to build out the system within a certain period of time or they can cancel your license. The reason they do that is to keep people and agencies for licensing a bunch of frequencies and not using them. It's often 6 months or a year before it will cancel out if not built. Again, whoever set up your license should tell you that.

If you can post your call sign, we could look up your license and tell you a lot, but you would be better off talking to a reputable radio shop than a bunch of strangers on the internet.