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RF linking


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Question on RF linking. I'm getting a good 5 mile portable coverage and about 10 mile coverage on mobile on my GR300 repeater. I'm only up 50' on 1/2" hardline with a 6 dBd comtelco antenna, and happy with the coverage on the limited height of the antenna. Base station operators could see somewhere from 10-20 mile coverage depending on their situations.

 

I have a friend that has a tower up and I'm kicking around the idea of a RF link. His station is approximately 10 miles from mine. We have good simplex signals between us. The idea is to provide better portable coverage for others operators, and ourselves, in the area. I have another GR300 that could be utilized at his location. Plenty of mobile radios for the link radio, and would only need the controller for the link radio.

 

Question is do both repeater sites need link capable controllers? Are repeaters on different frequencies? Do both sites need yagi's pointed at eachother? Is it worth it?

 

If anyone has any info on this setup please fill me in on details, thanks!

 

Ryan-WQVY669

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thanks Zap..

 

I'm thinking the shot gun link may work for us. going this way, let me see if I have this right:

1 repeater is on its own frequency pair , and the other is set on its own frequency pair DIFFERENT from the other? ex: RPT1 input 467.550, output 462.550.. and the other lets say input 467.575  out 462.575. link radio set  to the other repeaters pair?

 

 Can the link Yagi be on the same tower within close proximity to the repeater antenna? say 10' vertical separation? of course with the repeater antenna on top..without having any desense or any other interference to the repeater antenna?

 

The repeater that will have the link controller just has a basic Motorola RICK that has a accessory 16 pin port on it, not sure if  it best to use that port on the RICK and wire in the link controller to it or remove the RICK and just use the link controller. We are researching a few link controllers now, any recommendations that you may, or others may have used with good results?

 

Sorry for all the questions, and appreciate any help

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I have, I've been researching and reading the different ways members on here talk about their methods discussed here. All the talk with Linux this, Asterisk that, Pi those, URIx these, I believe may be a little over my head. I'm just starting out I have two repeaters and just trying to figure what will be the best way for "ME" to link them. I'm all for an internet link, I wish I could find someone with a plug and play set-up for GMRS, if there is PM me and lets talk.

 

But for now I think an RF link might be a lot less painless, for me anyways...only one way to find out!

 

thanks...Ryan

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It can be done but gets tricky with the frequencies we have to work with. I have 2 GMRS repeaters about 10 miles apart. Both TX on the same channel, but i do use different RX PL tones. On one end i do dump the RX audio into a gm300 on another channel and send it to the other site (utilize RICKS on both ends). This essentially lets me talk on both repeaters in a poor mans simulcast. I try not to use it often as there are some issues but its great to make a "call" to someone then we switch channels. The issue is if you are between both repeaters you will hear simulcast distortion, and really rough. I have played around with switching the TX on one of the sites, but the nice thing is I can hear someone calling where ever i am. 

 

I am lucky and have a 60' tower at one site so have plenty of seperation for the yagi. I also run filters on it, although its not the best. Remember we are talking within 1 MHz. Its not ideal but can be done. My next phase is actually siwtching out to a comparator and voting the audio.

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I can tell you my setup..

 

I have an M1225 Repeater setup on my Church, my buddy has his setup in the next city over, we've "Simulcasted" the two repeaters by a VHF link using two Wouxun KG-UV920P Cross Band Repeating Radios with yagi's, works pretty good with us. It was more of an experiment for us, but the same problems do occur with the distortion as kb2ztx mentioned..

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Easiest way is to utilize a repeater, link controller and link radio. The repeater you are linking to needs to be a different frequency than yours (causes some issues). Your link radio also needs to be using a yagi antenna. You should be able to do this at 1W in most cases but I wouldn't go higher than 5W.

 

The link radio is programmed (or channeled) like any other repeater you wish to use through your HT or mobile. The link port goes to the link radio and the controller controls the onsite repeater.

 

When the link is active, the remote repeater will key causing the COR circuit on the link radio to open and pass audio to the controller. The controller then keys the local repeater's transmitter and passes audio from the link radio. When the local repeater receives a COR signal, it keys both the repeater transmitter and the link radio (which in turn keys the remote repeater).

 

This system can be built upon and built upon. In this case the remote repeater would be the hub and the local a spoke in the hub.

 

 

Sent from my iPhone using Tapatalk

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The shotgun method is proving to be a challenge. I have 20' of vertical separation, link radio power is 2 watts on a beam, and still getting desense on the repeater when the link radio keys up. I'm using a CAT 250 controller, I even tried moving the yagi beam 20' away (horizontal seperation) and still not working. Do I need more seperation?

 

I refuse to give up!

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The problem with GMRS is you dont have lots of channels to choose from as you do in Ham radio. You have basically 8 repeater pairs. Drop in a UHF link and even with the best filtering it causes issues. We dont have VHF frequencies as a GMRS license to use so the best way to link is over IP.

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YOu didn't mention the height of the tower. The elevation of the tower above average terrain, or the expected coverage footprint of a UHF repeater at the tower.  If the site is of reasonable height and the terrain height is good you may well pull a 20 or better mile radius of coverage from that tower.  If that is the case, why tie up two frequencies by linking two repeaters.  You would be far better off to just put your repeater on that tower and be done with it.  Your coverage would increase and you would not be tying up two freqs with the same audio.

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