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Author Topic: Belden 9913F7 vs. Belden 7810A coax differences  (Read 2045 times)
N8EUI
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Posts: 146




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« on: September 20, 2003, 04:25:30 PM »

Can anyone tell me the advantages between these two feedlines?  I need some advice in order to make a decision which one to use for my horizontal loop.
I believe the 7810A (Belden RF-400) is similar to LMR-400.
Thanks,
Tom, N8EUI
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KC7YRN
Member

Posts: 161




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« Reply #1 on: September 24, 2003, 11:32:03 AM »

9913F7, RG8 sized, flexible, "low loss" but that's a relative term -- at 400MHz, it will misplace almost half your power in 100 feet. Foam dielectric. Some foam dielectrics make it hard to solder on PL259's and they leave you no margin for error on waterproofing.

7810A, somewhat lower loss but not dramatically so. Yes, intended as a competitor to LMR-400.

I'm not an expert here, can anybody more knowledgeable review my comments and/or add detail?
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KC7YRN
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Posts: 161




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« Reply #2 on: September 24, 2003, 11:36:24 AM »

Sorry, should have read more carefully.

For a horizontal loop I'd suggest, if possible, using some kind of open wire feed. "Possible" means you have room to take it off at close to 90 degrees and to route it several times its width away from anything conductive.

If you use coax, consider an autotuner at the feedpoint.

Play with some numbers at http://www.ocarc.ca/coax.htm, where there's an online calculator for coax losses depending on line length and SWR.
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K9KJM
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Posts: 2416




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« Reply #3 on: October 06, 2003, 01:36:54 AM »

What frequency do you want the coax to operate at??
For HF use, Belden 213 is still the best to use by
far.
For VHF/UHF the Belden 9913 series of coax has been
a dismal failure. I have had three different versions
that have proven BAD. I would not give them another
chance with that stuff! AVOID it!
LMR 400 is the coax used by commercial users. It is
the good stuff. But for any runs that get fairly long
(Approaching 100 feet or so) Try to get some good
used Heliax. 7/8" Heliax and connectors are now
available at most all swap fests for really good
prices. The higher you go in frequency, The more you
need to keep the feedline really as short as possible,
and also use the best feedline available.
I also see short runs of 7/8" Andrew heliax on Ebay
going for a good price every now and then.........  
But always check on shipping first, This stuff is big
and heavy!
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N8EUI
Member

Posts: 146




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« Reply #4 on: October 14, 2003, 01:12:11 PM »

Thank you all for your suggestions.

Tom, N8EUI
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W4QA
Member

Posts: 22


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« Reply #5 on: December 19, 2003, 09:28:21 PM »

Belden 9913F7 is in no way like the 9913 that some people have had trouble with.  9913F7 is an entirely different design -- different dielectric, different jacket, different shielding.  The older 9913 had an air dielectric that could suck up water if a connector was leaky -- also, a tight bend could "migrate" the center conductor.  However, when properly installed -- the "old" 9913 is still a super coax.

Belden 9913F7 has none of these problems and is arguably the best performing "RG-8 type" coax on the market today -- preferred by the military and the "3-letter" government agencies because of its extremely high quality.  There is a reason that Belden has the super reputation that they do in the Bell Operating Companies and the Government -- it is top grade.

Belden 7810A or RF-400 is similar to TimesLMR400 -- but has lower loss than LMR-400 as you go up in frequency.  Commercial users that use this type of coax in the GHZ range care a great deal about the power budget and .1 - .5 db can make quite a bit of difference.
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