UHF Repeater Coverage Question

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sigxbill

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I am a new HAM and am so excited about it, I want to put up my own 25 - 45 watt repeater for close group use in UHF band. I would be getting a good 10' antenna with 9 db gain. The good thing is I live on a hill. The problem is the hill is in the middle of canyon. The canyon ridges are about 1-2 miles from my house, and are about 350 feet higher than my house mounted antenna would be. The target locations are about 7 miles away, and are between 400 to 600 feet lower than the canyon ridges. The target radio operators would be using decent 4 watt HTs.

Is this communication scenario possible? Or is UHF too line of sight for the signal to overcome the canyon ridges?

Thanks in advance!
 

kayn1n32008

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There is an online coverage predictor, drop your location, elevation of repeater antenna, and see what you would get for coverage. I believe Radio Mobile has an online service for this.


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prcguy

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I used to live in the flat part of my town and ran low power repeaters with a 9dBd gain antenna on top of a two story building. I was at the base of an 1,100ft hill and could not talk into neighborhoods a few miles away that were down and behind the first ridges of the hill, which were around the 300ft level. I could however get about 10mi and sometimes much more in most other directions to mobile or base stations and up to about 5mi in some directions to handhelds.

I now live about 350ft up the same hill and have done over 100mi to handhelds in one direction and at least 30mi out to 100+mi to mobiles or base stations on UHF.

BTW, a 10ft tall UHF antenna would be hard pressed to reach about 6dBd omni gain, it takes nearly 20ft of antenna to get about 9dBd omni gain.
prcguy
 

jaspence

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There are other things you will need to consider. A repeater frequency pair needs to be coordinated by your state frequency coordinator. You also need some type of system, such as a diplexer, to keep your signals from mixing unless this is going to be a simplex repeater or you are using multiple antennas. With your altitude situation, the only real coverage will be if you can located the repeater on one of the high ridges.
 

Voyager

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Coordination is optional, and the device is a duplexer which is also optional if you use two antennas with adequate vertical or horizontal separation.
 

902

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Welcome to amateur radio, sigxbill - and welcome to one of my favorite parts of the hobby! I build repeaters, too, since the 80s and I haven't gotten bored with it yet.

Although coordination is "optional," a responsible repeater owner is a good neighbor who goes through the process.

A repeater - especially one that has very good coverage - is a big investment. A large repeater system may have tens of thousands of dollars invested in it. I guarantee that a coordinated repeater owner will not be happy with someone setting up within range on the frequency pair they are coordinated to - to the extent of potential litigation (yes, some people take it that seriously). My advice (which is worth as much as it costs): Do it right, or don't do it.

That said, many coordinators have what's called a developmental pair. That's a place where you can set something up to see if it works for your purposes, and then you can migrate it to a permanent assignment once you are sure it suits your needs. And, repeaters are not as popular today as they were 25 years ago. Coordinated spectrum is more than likely available and readily obtained in many areas of the U.S.

About your prospective site and system implementation, I doubt you'll have coverage beyond the peaks. There is some "diffraction" over sharp objects, but that's not usually a reliable mode of communication. You might find 6 meters to be a band that might work, although 6 meter portable radios aren't as efficient as 440 ones would be.

I'm guessing that doesn't matter as much as experimenting and learning. By all means, do it! You'll learn a lot, all of it can port into earning money as a technician, and you have room to scale things up or back as your interest and capabilities carry you. But take the effort to work within the framework that's out there. That puts you on the same par as all of the other repeater owners.

I'd also like to draw your attention to a great website where you will learn a great deal: Welcome to Repeater Builder Dot Com You've probably been there, but if you haven't, there are volumes there about how to build a repeater from radios to antennas and everything in between.
 

krokus

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If you want to talk one side of the ridge to the other, the repeater would need to be someplace that can see both locations.

Another option is to use IRLP between base radios.

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N4DES

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If you want to talk one side of the ridge to the other, the repeater would need to be someplace that can see both locations.

Another option is to use IRLP between base radios.

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Other option is for him to look to see if there is an existing repeater that someone may have in service already that is begging for some new voice traffic on it.....
 

elk2370bruce

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Coordination is optional, and the device is a duplexer which is also optional if you use two antennas with adequate vertical or horizontal separation.

That is not always the case. In high density areas (like NY/NJ) its not really an option. Better to be coordinated than begging to get nastygrams about interference with some other repeater.
 
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