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Author Topic: Digital for a Link?  (Read 5770 times)
AF6D
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« on: June 11, 2017, 01:22:27 PM »

I need to link two or more 2m sites together and I don't want to use the internet because in the event of a Southern California emergency, like an earthquake, the lines will likely be down. The distance is far enough that Ubiquity probably is not a solution. Using old school 430 something or even 900 something for linking seems to be more appropriate. It is effectively would be a repeater in between a repeater. I haven't done this before. Since this would be repeater traffic I would need to run the radio with less transmitter power. But then we get variables like thunderstorms and whatnot with static crashes - not an issue on 430 but I know that at 900 megahertz refraction can be an issue and we get more than enough snow and rain for this to be a possibility.

I'm worried about the distance and I can't go direct line of sight. I have to go to a intermediate site. For example site A to site B to site C and then the reverse. Would it be better to run these as 20 kilohertz analog links or as 12.5 kilohertz digital links? My thinking is that the goal would be running lesser power but maintaining legibility regardless of conditions. Am I just overthinking this? Should I just run straight analog with horizontal yagi's? How about the audio? I can learn by actually doing it or by knowing what to expect. I imagine level control is going to be very important.
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KG4RUL
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« Reply #1 on: June 11, 2017, 01:40:56 PM »

Start by looking at this site: http://www.repeater-builder.com/rbtip/
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AC7CW
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« Reply #2 on: June 11, 2017, 04:57:06 PM »

Have hams experimented with passive repeaters? [back to back yagis]
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Novice 1958, 20WPM Extra now... (and get off my lawn)
AF6D
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« Reply #3 on: June 12, 2017, 03:32:44 AM »

Start by looking at this site: http://www.repeater-builder.com/rbtip/

Any repeater owner is well familiar with that site. It does not answer my question. Would you like to take a try at it?  Wink
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AF6D
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« Reply #4 on: June 12, 2017, 03:34:50 AM »

Have hams experimented with passive repeaters? [back to back yagis]

I have thought of that but using corner reflectors. I just don't know if it is worth the time. I know that the railroads (at one time?) used passive repeaters. But should I consider like P25 for the back-haul that will make it more reliable and less opportunity to mess with?
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K4JJL
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« Reply #5 on: June 12, 2017, 09:53:02 AM »

Have hams experimented with passive repeaters? [back to back yagis]

I set up a couple of these for GA Power years ago for use in the power plants.  Only really worked on high band.  UHF was way too lossy.
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AF6D
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« Reply #6 on: June 12, 2017, 09:11:52 PM »

And UHF is the link band. AND...   25 miles away and then another 35 to the other site. That's why I asked about RF links.
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N8EKT
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« Reply #7 on: June 13, 2017, 03:44:55 PM »

analog with horizontal polarity is still your best bet

and I would link over 220mhz to keep the path loss down

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KD4LLA
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« Reply #8 on: July 09, 2017, 08:38:59 AM »

It's been 17 years since I was in the Fairbanks, AK area, but there the KL7KC club had multiple repeaters linked by 220mhz.  I just checked the KL7KC web page and there is not much left of the repeater system it seems.

You might try contacting someone there at the Arctic Amateur Radio Club.
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