Actually, I believe that the RG-designations are no longer used by the
US military at all. Mil-C-17 now??--and I'm not sure any current ones
are polyethylene (and not Teflon) dielectric. As John points out, RG
numbers have been somewhat corrupted! But in general, "RG-213/U" and
"RG-8/U" should both be solid-polyethylene dielectric cables with the
same diameter and the same stranded inner conductor and single copper
braid outer, and therefore should have the same attenuation per unit
length, nominally. There will be minor variations from lot to lot, or
larger variations if the coax was made poorly. "Reference Data for
Radio Engineers" says of RG-213, "Formerly RG-8A/U."
Foam dielectric cables, perhaps called "RG-213-type" or "RG-8-type,"
have lower loss for a given outer conductor diameter because the inner
conductor is larger diameter and therefore has less resistance than
with solid dielectric. (Similarly for Belden 9913-type cables.) But
they may not be able to handle as much power, because the foam
dielectric may be enough better a thermal insulator that the inner
conductor still gets as hot or hotter at a given power, and that's the
limitation. Also, you should be careful with bends in foam dielectric
cables, because they can cause the center conductor to go off-center;
that's especially bad if the cable's used at VHF/UHF. There's plenty
more about the subject, but hope this helps a bit.
Cheers,
Tom
"John Passaneau" wrote in message ...
Hi:
RG-8 used to be a military specification cable but the military dropped it
in favor of a new specification called RG-213. They are very similar coaxes
in general, but manufactures are free to make any cable they like and call
it RG-8 so the quality and consistency can vary widely. Also RG-8 with foam
a center insulator, and all the other variations are not nor never were
MilSpec.That does not mean that all RG-8 cables are crap, but it could be
and it depends on the manufactures idea of what kind of cable they want to
sell. On the other hand RG-213 as a current MilSpec cable is a higher grade
cable and is more consistent from manufacture to manufacture. My feeling is
that if I'm going to go to all the work of installing a antenna, I want to
use the best material I can. So I use RG-213. But my favorite coax is Davis
RF Bury Flex, http://www.davisrf.com/ . It's a good coax that has low loss
and a very tough jacket. I have 500 feet of it in my antenna system and so
far I'm very happy.
--
John Passaneau W3JXP
State College Pa
This mail is a natural product. The slight variations in spelling and
grammar enhance its individual character and beauty and in no way are to
be considered flaws or defects.
"Jerry Bransford" wrote in message
news:moUAb.29779$Bk1.25134@fed1read05...
Ok so I'm getting back active with my ham gear and while looking into a
new
HF antenna, discovered a new cable type being recommended here and there,
RG-213. What is so much better about RG-213 than what I have used so much
of over the years, RG-8? TIA. 
Jerry
--
Jerry Bransford
To email, remove 'me' from my email address
KC6TAY, PP-ASEL
See the Geezer Jeep at
http://members.cox.net/jerrypb/