UnwiredTX
join:2005-11-09
Cameron, TX
| Question about coax size
OK. So I've lurked and looked and can't find anything pertaining to this.
Background: We've been using 7/8" Andrew heliax for years (for towers, as far back as when we were doing 2.4 backhauls). We switched backhauls over to 5.?Ghz about two years ago... and continued to use 7/8". So, one day I'm looking at ordering more cable, and notice on a dealer's website that 7/8" is not suited for above 5Ghz.
I had been working under the assumption that because it DID work, it must be okay. Stupid, I know. We had a brief fling with 1/2", and I KNOW that didn't work well, as most of our runs are about 120'. So, my question here is... for 5.whatever Ghz (120' runs), should we be using 5/8", or what?
I know I can find lots of theoretical info on manufacturer's and dealer's sites, but I want to put this question to a crowd who has field experience with it.
Also, would 5/8" be acceptable for approximately 150' runs on 2.4Ghz?
Sorry for the long post, and thanks in advance for any words of wisdom. |
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John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
 ·CenturyLink
| The cross-sectional diameter of the coax is the issue. As the diameter gets larger, it approaches the wavelength of the frequency in use.
Use the charts from a reputable manufacturer of cable. After all, they are experts in the operational characteristics of their cable and their advice should be followed for the best results.
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A is A |
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Diddy1
join:2003-07-19
Sidney, NE
| said by John Galt  :The cross-sectional diameter of the coax is the issue. As the diameter gets larger, it approaches the wavelength of the frequency in use. Can you clarify the theory behind the diameter of the coax in relation to wavelenght? You've sparked my curiousity and I need to learn more of the technical side. Any links to relevant info.? I know it sounds naive, but gotta learn, learn and learn.
Aaron |
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slipstream1
Premium
join:2005-11-15
Jacksonville, TX | reply to UnwiredTX
Go to Andrews website. They have all of the white papers and technical documents that can explain this to you. It looks like 5/8" coax is the way to go, but you lose almost 5 db per 100'. |
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AMD Phreak
Premium
join:2003-12-14 | reply to UnwiredTX
5/8's is best suited for 5.8 GHz. |
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cmaenginsb
Premium,MVM
join:2001-03-19
Palmdale, CA
| reply to UnwiredTX
We used 5/8" for all our 5GHz installs until switching to radios that supported POE or an IDU/ODU architecture. The longest run I did with it was about 80' and it worked ok.
7/8" appears to be marginally acceptable for lower 5Ghz radios according to Andrews previous data, I haven't looked in a while though.
It's entirely possible to create a link using 7/8" and 5.8Ghz, the problem is from my understanding the VSWR will change to an unacceptable level causing damage to the radio over the long term. If you have a radio using one of those coax runs "go bad" with no apparent reason it would be one possible cause.
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CCNA, Comtrain Certified Tower Climber |
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electric6
@sbcglobal.net
| reply to John Galt
The cross-sectional diameter of the coax is the issue. As the diameter gets larger, it approaches the wavelength of the frequency in use.
Actually The operating voltage determines the proper diameter, and the upper frequency is determined by the outer shield construction. |
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John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
·CenturyLink
| said by electric6 :
Actually The operating voltage determines the proper diameter, and the upper frequency is determined by the outer shield construction.
Under most "normal" circumstances...but in the WISP world frequency is the issue, not power.
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A is A |
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