Hi Jim,
Good rant.
I have mil-spec (MIL-C-17/6B imprinted) RG11/U on spools in my garage. I'm
trying to remember the mill, probably Carol or Times. It's not very new,
I've had it several years, probably mfd in 1990 or so; but, it's unused and
has been stored in a dark, dry environment so is "new."
Nothing special about the mil spec other than it's solid PE dielectric with
real copper conductors, unlike a lot of commercial equivalents (which may
actually be better in some ways) that are cellular PE, or have clad aluminum
conductors and other stuff. The mil-spec stuff is more mechanically robust
by design and materials used; doesn't make it better for our purposes, and
probably makes it a whole lot worse for CATV use. For CATV, the quad
shielded RG6 the cable companies use blows away RG11/U in just about every
respect, including cost.
That's why when I heard the application, I recommended against using RG11/U.
The "thick net" cables used commercially nowadays are better in every way I
can think of except mechanical strength. The old solid poly stuff is
stronger, in that you can drive a car over it and it still works.
73!
Steve WB2WIK/6
-----Original Message-----
From: Jim Lux [mailto:jimlux@earthlink.net]
Sent: Wednesday, February 09, 2005 10:51 AM
To: TowerTalk@contesting.com
Subject: [BULK] - rant on "mil spec" wasRE: [BULK] - [TowerTalk] RG-11
Source?
At 09:19 AM 2/9/2005, Steve Katz wrote:
>Tower Talkians,
>
>Anyone have a good source for quality RG-11?
>
>::I have mil-spec RG11/U on spools. How much do you need?
I don't want to beat up on Steve here, but he triggered an area near and
dear to my everyday work.
Just a quibble here about the term mil-spec... (a similar phenomenon occurs
with high rel electronic parts, except there, it's with reference to 883B,
Class S, etc.)
There's nothing special about mil-spec stuff. It just means that someone,
somewhere who had to buy something for the government wrote a spec, got it
approved, etc. For instance, MIL-P-43988 is the 10 page mil-spec for toilet
tissue in MRE-Packets (actually, it's been superseded by ASTM-D3905-1993,
Toilet Tissue, Industrial). We also, of course, have to ask the question,
"Whose military?"
Of course, the military tends to buy things that can operate in harsh
environments, so if you've picked the "right" mil-spec that might imply a
better quality (or more appropriate) widget. However, for some things, you
might not want the mil-spec product: perhaps non-mil-spec Charmin might
provide a better toilet tissue experience than ASTM D3905 compliant
stuff?). A good example is MIL-STD-810, which defines a variety of
environments for equipment; Be aware that some of those environments are
pretty benign, so claiming "meets MIL-STD-810" for your radio might not be
all that impressive, however, some of those environments are pretty abusive
One aspect of using industry standard designations (and that's
fundamentally what a mil-spec is) is that there is the (legally
enforceable) assumption that the product being sold has been tested or
verified to comply with the spec. Here, we get into such fuzziness as
"designed to meet". The problem comes in about whether you can really
sell something as complying with a specification that no longer exists
(officially). I couldn't do an electrical design for a client and claim
it's "code compliant" if it met the 1981 NEC.
And this is where the problem lies. There is no such thing as "mil-spec"
RG-11 any more... Just like there's no such thing as mil spec RG-8, RG-213,
etc. All the polyethylene insulated cables were purged 10 or more years ago.
Back in August 1993:
"
CABLES, RADIO FREQUENCY, FLEXIBLE COAXIAL, 75 OHMS,M17/6-RG11, UNARMORED,
M17/6-RG12, ARMORED
..
MIL-C-17/6B is inactive for new design. For new designs use specification,
MIL-C-17/181B, Cables, Radio Frequency, Flexible, Coaxial, 75 Ohms,
M17/181-00001 Unarmored, M17/181-00002 Armored.
The Qualified Products List (QPL) associated with this inactive for new
design specification will be maintained until acquisition of the product is
no longer required whereupon the specification and the QPL will be canceled.
"
Not to say that you couldn't legitimately claim that you've got cable made
to a particular obsolete spec. Or, you could say, I'm selling coax with
the following characteristics, and then have your own mfr spec that happens
to copy the parts of MIL-C-17/xxx needed.
And, you might use the (obsolete) RG number as a shorthand to illustrate
the type of cable. i.e. "RG-8 type cable" This is what Belden does...
their cables are all made to Belden specs, and have specific Belden part
#s, and they get identified as "Type 11 cable", meaning, looks a lot like
what you used to buy as RG11, in terms of impedance and physical
dimensions, but not in terms of much else.
Jim, W6RMK
(I'll be happy to send the 400kB Mil spec for TP to anyone who wants it...)
_______________________________________________
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_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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