One of us is confused. I've never seen RG8X with "a thin aluminum
Aluminum Foil and only very few thin copper wires as braid shield." All my
RG8X is foam dielectric with standard copper shield and various forms of
jackets depending on manufacturer.
Here's a URL to Belden's RG8X specs:
Note the description of the shield as being "copper braid."
As for power-handling capability, I've seen conflicting specs on that.
Strictly speaking if the SWR is 1:1, under 10MHz RG8X is spec'd to handle
1500W. By the time you get to 50MHz (yeah, right!) it's down to 800W. On
the other hand, those ratings QUICKLY degrade when the VSWR starts climbing
above 1:1. This thread started with the context of a 3/2 wave antenna.
Such an antenna is not going to provide a 50-ohm feedpoint (or it would be
purely accidental if it did, height dependent). Given RG8X's voltage rating
of about 300V, practically speaking it cannot handle the legal limit.
My personal experience with mysterious incidents of shorted feedlines using
RG8X on both 7 and 21 MHz at 700W leads me to believe it's not a good choice
for legal-limit usage on any practical antenna system.
So, I guess I respectfully disagree :) This might be yet another example of
what works on paper and what fails miserably in actual use.
| -----Original Message-----
| From: email@example.com
| [mailto:firstname.lastname@example.org]On Behalf Of email@example.com
| Sent: Thursday, March 01, 2001 8:57 AM
| To: firstname.lastname@example.org; email@example.com
| Subject: RE: [TowerTalk] Coax Rating
| The reason why an RG8X insn't raccomandable at high power levels is
| because of a shield that's made of a thin aluminum Foil-Polyester Tape-
| Aluminum Foil and only very few thin copper wires as braid shield.
| The foam dielectric hasn't significant losses and a foam cable of the
| same size of an RG8X, but with a classic copper braid or a more
| consistent foil (aluminium or copper), would safely withstand much more
| than US legal power at 7 MHz, and roughly twice the power of an RG58
| expecially at 30 MHz and above.
| Mauri I4JMY
| > ---------- Initial message -----------
| > From : firstname.lastname@example.org
| > To : <email@example.com>
| > Cc :
| > Date : Thu, 1 Mar 2001 08:35:18 -0500
| > Subject : RE: [TowerTalk] Coax Rating
| > Ted,
| > Be careful. Yes, I have had a meltdown as you call it, using some
| > hamfest-grade RG8X on a 100 ft run feeding a 1/2 wave on 40. The
| power into
| > the feed line was likely about 700W. I don't know whether this
| > while operating on 40 or 15. And here's the caution...you might
| squeak thru
| > with a perfectly flat SWR. But with 3/2 waves I'd bet you will not
| > that. Any SWR will significantly increase the probability of zapping
| > line.
| > As I recall, the rating is about 300V across that foam dielectric.
| > sure of that than the above. I believe RG58 is actually more
| forgiving than
| > RG8X in terms of power handling.
| > I'm using RG8 now, with a convenient tree to help support the weight
| so the
| > antenna doesn't have to see it all.
| > 73/Gary W2CS
| > | -----Original Message-----
| > | From: firstname.lastname@example.org
| > | [mailto:email@example.com]On Behalf Of Ted & Joyce
| > | Sent: Wednesday, February 28, 2001 11:39 PM
| > | To: firstname.lastname@example.org
| > | Subject: [TowerTalk] Coax Rating
| > |
| > |
| > | Am planning on trying to put up 3 1/2 waves on 40mtrs. and wonder
| > | anyone knows the maximum power that RG8X will handle on a relatively
| > | short run less than 100 feet....I know I would probably be better
| > | with something like 213 or the like but am concerned with the weight
| > | factor....Anyone had any major meltdowns using the lighter feed
| > | Thanks,
| > | Ted K9HUH
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