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Linking


mainehazmt
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Hi all long time since I have posted but I have a question about linking. I have a pretty good size dead spot that I can not overcome. And it happens to be right in an area where I hunt fish 4 wheel and just veg out at. If I get on top of the hill I can hit my repeater no problem but in the lake area (big farm pond actually) 0 coverage. I have another repeater I can put in place and run it solar but can and how can I link them or can I ? Thanks again

John

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You can. There's nothing that says you can't in the current revision of the rules, most today are primarily focusing on internet linking though. In this case, it sounds like a good old fashioned (still see it occasionally today) RF link would be the best option. 

 

To sum up the Repeater Builder site on RF linking, there are 3 basic types of links. Point to point (simplex), half-duplex (shotgunning), and full duplex (link repeaters). In a point to point link, repeaters are linked through a link radio on each repeater. The radios run simplex (often with split PL/DPLs). When on repeater is keyed, it keys the link radio which sends a PL/DPL that only the other link radio receives, keying that repeater transmitter. The downfall to a point to point system, it can't be expanded to any more than two repeaters and it's questionable for use on GMRS the way the rules are currently laid out. Next is shotgunning where a link radio simply transmits on the input/output of the next repeater. You start out with a "hub" which is just a basic repeater. The next repeater's link radio transmits on the hub's input and listens to it's output. You continue like this down the line (wouldn't recommend it for more than about 2 or 3 hops). The finial link setup is a full duplex system. Basically it's another repeater…just for linking. Every site consists of a local repeater and a link repeater. The link repeaters run at 100% duty. They use PL detect to keep from keying the local repeaters.

 

The benefit to the first and last setups, they are band independent. You could use a common link band (say 900 MHz, 420 MHz, 220 MHz, etc) for all of the link radios where the shotgunned link radios have to be on whatever band the next repeater down the line towards the hub is. However, shotgunned is the most applicable method in terms of staying within the confines of the rules in Part 95A.

 

So, you generally need a controller that will handle links such as the NHRC 3.1, NHRC 4 and up, Electra 2000, RC2103, etc. so you can turn the link on and off, a link radio (1-5W with a yagi antenna is generally plenty), and a repeater. It is important to take into consideration power consumption (may want to make the off-grid repeater the hub), and the fact you will need separation between the repeater's antenna and the link radio's antenna.

 

The Repeater Builder site has a good page about off-grid repeaters. It's a good read if you haven't read it yet.

http://www.repeater-builder.com/tech-info/solar-power-thoughts.html

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Easiest is shotgunning.

 

If your home repeater is easily accessible, I'd add a link capable controller with a UHF radio running about 1-5W on a +9 dBd antenna. Program the link radio to the input and output of your remote repeater, point the yagi towards the remote repeater, its advised to use a program to make sure LOS is capable for the link, then set your remote repeater up (don't bother with a hang timer as the repeater with the controller on it will handle that). 

 

Shouldn't have to say, you probably 10-15 feet of vertical separation for the link antenna from the repeater and you can't use the same pair for both repeaters.

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Easiest is shotgunning.

 

If your home repeater is easily accessible, I'd add a link capable controller with a UHF radio running about 1-5W on a +9 dBd antenna. Program the link radio to the input and output of your remote repeater, point the yagi towards the remote repeater, its advised to use a program to make sure LOS is capable for the link, then set your remote repeater up (don't bother with a hang timer as the repeater with the controller on it will handle that). 

 

Shouldn't have to say, you probably 10-15 feet of vertical separation for the link antenna from the repeater and you can't use the same pair for both repeaters.

i keep reading and re reading lol. Seems I'm missing something in my head. Might be the drugs the VA has me on. Maybe I need a picture lol. Maybe I'll get it figured out by May June when I can get back to my campsite on the farm. Too much snow there now anyway
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Uses the frequency of the one you want to link to. So you basically setup a low power radio to use the remote repeater and then just power through there with a yagi antenna. 

 

You will want to make sure you have line of sight. Factor in your line loss, antenna gain on both ends, calculate the distance. I can do a little work in splat to get distances and estimated receive signals with antenna gain factors and what not if needed.

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Back a couple of years ago i contacted a gentleman at the FCC corp office asking if i could use a seperate link radio to join 2 or more gmrs repeaters. His answer was yes as long as they remain within your group of frequencies. So i'm wondering why everybody keeps beating a dead horse?

Just saying. Feel free to do the same by contacting your fcc office.

 

Jeff

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Back a couple of years ago i contacted a gentleman at the FCC corp office asking if i could use a seperate link radio to join 2 or more gmrs repeaters. His answer was yes as long as they remain within your group of frequencies. So i'm wondering why everybody keeps beating a dead horse?

Just saying. Feel free to do the same by contacting your fcc office.

 

Jeff

Wouldn't be bad to get the name of the guy you talked to as well anytime you get info from an FCC office…cover you bases in case you ever need them.

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Not exactly about linking, but I was trolling the eBay the other day and a guy was selling a "GMRS cross band repeater". He had 2 M120 (a UHF and a VHF) Motorola mobiles, a home brew criss cross cable, and was showing how to make it work with a Chinese radio which was showing 462.xxx and 146.xxx. I wanted to send him a question on his listing asking if he knew that was illegal...but I get tired of fussing. He knows, I'll put money on it. Of course, it's not illegal until he/someone transmits. 

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