To: | Steve Katz <stevek@jmr.com>, TowerTalk@contesting.com |
---|---|
Subject: | RE: [BULK] - rant on "mil spec" wasRE: [BULK] - [TowerTalk]RG-11 Source? |
From: | Jim Lux <jimlux@earthlink.net> |
Date: | Wed, 09 Feb 2005 14:08:43 -0800 |
List-post: | <mailto:towertalk@contesting.com> |
At 11:42 AM 2/9/2005, Steve Katz wrote:
Hi Jim, There you go.. it was probably made before they cancelled the spec. It was the PVC jackets that were the problem apparently. I also just learned that the real important difference between old MIL-C-17 cables and new MIL-C-17"G" cables is that the new standard is much more sensitive to cables with periodic impedance bumps, because they require swept frequency measurements, as opposed to spot frequencies. The way that cables are made apparently tends to result in periodic bumps (it's made on machinery with round pulleys, etc., and if there's a lump or a seam, it gets repeated every wheel rotation) which make a fairly narrow band problem (a resonance issue... like having a hundred section filter all tuned exactly the same). The old test regime wouldn't necessarily hit those "dead" frequencies. Another thing I learned is that there are NO Mil spec RG series cables anymore. Not just the PVC jacketed ones. Now it's done with a QPL (Qualified Products List), and anything labeled as RG is, almost by definition, NOT mil spec (at least today.. that Korean War vintage spool of RG-8 all you TTers have sitting in the back yard, just in case, was made according to the spec at the time). 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. There's some pretty tough armored stuff with foam dielectric around. However it's very, very expensive. Solid PE dielectric is probably a pretty good compromise between cost, ruggedness (at least laying flat), and so forth. _______________________________________________ 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. _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk |
<Prev in Thread] | Current Thread | [Next in Thread> |
---|---|---|
|
Previous by Date: | Re: [BULK] - [TowerTalk] RG-11 Source?, Tom Rauch |
---|---|
Next by Date: | Re: ***WARNING**** DISHONEST SELLER K4IDC/KB4IDC :[TowerTalk] LargeMast For Sale...last one, Bert Rollen |
Previous by Thread: | Re: [BULK] - rant on "mil spec" wasRE: [BULK] - [TowerTalk]RG-11Source?, Jerry Keller - K3BZ |
Next by Thread: | Re: ***WARNING**** DISHONEST SELLER K4IDC/KB4IDC :[TowerTalk] LargeMast For Sale...last one, Bert Rollen |
Indexes: | [Date] [Thread] [Top] [All Lists] |