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Author Topic: Link Repeater  (Read 8670 times)
AF6D
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« on: January 12, 2014, 01:45:10 PM »

Today is one of those days that I sincerely dislike being the FNG that has to rely on others. In this case with their own plans.

We are building a three site (for now) voted / simulcast network using Allstar. It will have a 900MHz parallel link system o that when the San Andres earthquake hits and all of the Internet goes down we will have service. As it stands our site company has VLAN over microwave and a Intranet.

To my question.

We intend to install a 900MHz repeater at the main site and then at the current two subordinate sites. These sites would talk back to the link on a reversed pair. My associate insists that the main 900MHz repeater cannot b used as a repeater and I ask why not? Well, the other two will be transmitting creating a loop... yada, yada. Such would be the case if another subordinate site was talking to the main repeater (link) keying up the other subordinate repeater (link, inverted.)

So why can't the main repeater be used as an actual repeater? How is it any different than talking in on 2 meters and keying up the two other 2 meter machines by way of Allstar or the parallel 90 system?
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AF6D
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« Reply #1 on: January 14, 2014, 10:25:14 AM »

It looks like Jer Bro answered this question and may have realized that it was all wrong. and deleted his answer Smiley

The question was not whether or not one pair may be used to communicate because I already know and am building an Allstar system of voted simulcast.

The question again was asking why the link repeater in the middle as a backup to Allstar cannot be used as a repeater. My associate tells me that it cant. That when traffic comes in on the 2m machine, no matter which one, it brings up the master link machine in the middle and is being listened to site CD, so it also comes up. Therefore I think that if someone comes up on any one of three 900 machines that link through a RC-210 they would be heard on all three RC-210's and thus all 2m machines and all 900 machines.

Wouldn't the 900 machines be unvoted/simulcast but a linked repeater system nonetheless if each RC-210 controller removed them from their 2m machines?
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HURRICAINE
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« Reply #2 on: January 14, 2014, 10:42:37 AM »

It looks like Jer Bro answered this question and may have realized that it was all wrong. and deleted his answer Smiley

The question was not whether or not one pair may be used to communicate because I already know and am building an Allstar system of voted simulcast.

The question again was asking why the link repeater in the middle as a backup to Allstar cannot be used as a repeater. My associate tells me that it cant. That when traffic comes in on the 2m machine, no matter which one, it brings up the master link machine in the middle and is being listened to site CD, so it also comes up. Therefore I think that if someone comes up on any one of three 900 machines that link through a RC-210 they would be heard on all three RC-210's and thus all 2m machines and all 900 machines.

Wouldn't the 900 machines be unvoted/simulcast but a linked repeater system nonetheless if each RC-210 controller removed them from their 2m machines?

You never mentioned a two meter machine in your question - don't know who this jer bro person is - but you shouldn't pick on people when you are asking for help buddy!  10-4
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AF6D
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« Reply #3 on: January 14, 2014, 12:30:00 PM »

@Hurricane, who is actually Jer Bo that deleted his initial reply, I didn't pick on you at all. I got eHam's email of a reply and it contained your reply. When I got here the reply was gone, albeit totally off track. I never asked about what you answered. I asked why a link system can't be used as a three repeater system. Allstar is our main vote/simulcast solution and 900 is our back-up. 2m has nothing to do with the original question that today I gave further detail on. But then you tell me of how a WAN works but I am a Network Engineer and the owner of a substantially sized web hosting and digital content streaming firm. Jer Bo or Hurricane, or whoever you are, you really kind of stepped on it here.

Lastly, I don't need your rude and profane private message that has been reported to the Administration. Please do the rest of us a favor and not reply further.

Quote
from Jer Bo AKA HURRICANE]
Lets start out with the basic's.
Did you visit the repeater builder.com web site?
http://www.repeater-builder.com/rbtip/

Kevin is a very knowledgeable person and can help answer many questions about VOIP and All Star since his system - WAN is connected to the All-Star system.
http://www.wanrepeater.com/

I think if I understand the question correctly is why can't all your repeaters talk and listen on the same frequency?  am I correct?

Well first you have to understand radio and FM radio since this is what you are dealing with.

http://en.wikipedia.org/wiki/Frequency_modulation

A repeater operates on both an input frequency and an output frequency.

If you put multiple inputs into one frequency, the sum and total of those inputs mixes together and heterodynes ( mixes together ) and all you are left with is a bunch of noise.

 Just think of dirt and water - makes mud.

Output is the same thing, if you have two identically strong signals on the same frequency, they would mix together in the other persons receiver and all they would have is mud (noise).

Repeaters are built upon a group of coordinated frequencies, you only hold one or two frequency pairs - from what I gather.
All 900 mhz?..  Or is just the link frequency 900 mhz?

In order to link multiple repeaters together, you would need individual pairs of frequencies for each repeater that had enough separation between them that they would not interfere with your main repeater as well as everyone else's already coordinated repeaters.  I don't know how many pairs of frequencies there is available to amateurs in the 900 mhz band...

The way the Wide Area Network - WAN works is that it converts an analog signal into a digital signal.  That signal is then sent via the internet to the other machines, that has a internet connection and a computer that converts the signal back to analog - kind of like Echolink, but not really.  Echolink has crappy audio where as All-Star has better audio..

There is a group of repeaters linked to the Wide Area Network called the Target System - that is RF linked to the Hay's Mill's repeater via RF, but that is because in Maryland and West Virginia you can have two repeaters 20 miles away from each other and as soon as you go over the crest of the mountain you fall out of the repeater.  But each repeater is on its own separate frequency pair.

http://www.kuggie.com/target/

 Steve Henke would be the guy to talk to about the audio portion of the All Star system - because he is the one that worked on the audio scheme.
http://www.wanrepeater.com/

The problem you have with a system like what you propose is keeping the system running after some type of catastrophic failure.

Repeaters are mans monument to stupidity.
You have to believe that if everything else is gone or is not working, neither is the repeater going to be there or working.

Two prime examples is 911 - New York City and Hurricane Katrina and Louisiana / Mississippi where everything was flooded or blown away and there was no electricity and no fuel delivery and no towers left to operate off of.

Linking repeaters together is not as hard as trying to keep the internet going.  I would prefer RF to VoIp...

If you have three towers and one main repeater,
 the other two - voters, listens on the main frequency or an entirely different frequency and then talks to the main repeater on a separate frequency other then the input frequency of the main repeater and sends the received signal back from it's antenna, which also uses a different PL*  (CTCSS) to the main repeater via a separate rf link frequency and cannot transmit a output signal on the same frequency as the main repeater.   They would heterodyne.

A voter only listens where as a linked repeater talks and listens.
Would I use 900 MHz?   Not unless it was definitely line of sight.

Then you need to understand how line of sight communications works and how dust, rain, wind, flocks of migrating birds, airplanes, tall buildings, snow, and what ever else can and will block your reception = even if just momentarily.  What if one of the other towers fell down or went offline - how would you communicate with others in that area?  Two meters simplex - at least everyone with a license would have some type of radio..

Why can't they all talk and receive at the same time? , well they can all talk, but only if just one is receiving with most types of schemes other then the one used with the All-Star / Wide Area Network.

With the Wide Area Network, because it is not truely RF but VoIp, it acts much more like a telephone ( half duplex) where each voice is heard, much like voices in a room at a party.   It does not heterodyne as long as those two people are not on the same repeater.
This is because the analog signal has been changed into a digital signal at the first repeater site (voter) and then converted back into a analog signal at the second repeater site. (main repeater)

Its not much at all like REAL amateur radio, but is a lot more like talking on the telephone. 
It allows the lazy lids with the Technician Class License to use their walkie-talkies to talk long distances to each other without having to learn anything about radio or do anything like buy a real radio and put up a antenna and rely on line of sight communications, which if they are in a mobile or in a real crappy place,  or in the middle of a city somewhere, they wouldn't be able to talk more then a couple of blocks with just a hand held radio.

My question would be where are you going to get all the hand held 900 mhz radios from to get them into the hands of every amateur in your neighborhood?   Everybody has two meters but I don't normally even see any 900 mhz equipment out there.

More replies may be posted, but you won't receive any more notifications until you read the topic.
./quote]
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NJ1K
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« Reply #4 on: January 26, 2014, 06:27:15 AM »

My guess, if I am understanding your network correctly, depends on whether your 900 mHz link are full duplex or half-duplex.  If they are full-duplex, I envision that when you transmit into the "hub", the hub transmission in turn brings up the slave link repeaters that in turn transmit back into the hub, interfering with your own input...

On the other hand, if your links are half-duplex, what you are proposing should work.

Hope that helps.
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AF6D
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« Reply #5 on: January 26, 2014, 03:54:34 PM »

I don't to sound argumentative as I ask questions. Really, I don't. You are absolutely correct that I envisioned the opposite repeaters, 2 and 3, as half-duplex with only the master as a full duplex repeater. This would allow the main to be used as a 900MHz machine.

But then the issue comes up of maintaining control of the repeater by being able to break in at any time.

I am a rookie with much to learn. As such I have an idea and ask questions regarding it so that I may learn. It seems that those with experience have ego issues and don't like to be "questioned." I don't see it that way at all. The stupidest question is the one not asked. Some of learn by making stupid mistakes while others learn by asking stupid questions :-)

Thank you for a polite reply.
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NJ1K
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« Reply #6 on: January 26, 2014, 06:33:47 PM »

I am not sure what you mean by "control of the repeater".  To me, control means "a separate control link" on a different frequency or by wire-line, or something else.  Thus, maintaining control is always possible even with traffic on the repeater. 

Assuming half-duplex links, if one brings up the hub directly, then everything will be repeated on the other repeaters and vice-versa.  I don't personally see a problem, but then again, I don't know how your entire network is designed...
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AF6D
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« Reply #7 on: January 26, 2014, 09:25:07 PM »

He wants to use the 900link as the back link and control while Allstar handles the voting and simulcast. The 900 would also serve as the backup in the event of an Intranet failure - a microwave system already in place. We also have a 440 link receiver as well.
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