HI TTers: Ref to several observations and questions here recently: J.P.,
W2XX hits it on the head as noted below ref Mil Spec not being synonymous
with buriable. No PVC outer jacketed cable should be buried, only
Polyethylene, Polyurethane, and some other exotics.
Thanks for the remark about BURY-FLEX Tm which I designed and Press Jones has
worked hard with our manufacturer to even further enhance the close cell
foamed dielectric, in terms of increasing an already noteworthy velocity
factor.
Please note that BURY-FLEX Tm is not only highly advantageous to burying and
low loss. Many customers buy it for the low loss characteristic as well as
the fact that it is totally non contaminating as PE does not have harmful
plasticide agents. Aslo feel free to run it through ponds, etc.
To answer the other question about what does Andrews use for jacketing on
Heliax: both Heliax and Times LMR uses PE also as used in BURY-FLEX Tm. The
only exception is when certain fire retardant requirements apply, in which
case a halegonated version of PVC is used. Obviously the fire retardant
requirements would not apply in a buriable or outdoor situation and PVC is
not buriable.
As long as you don't expect an errant sharp spade shovel, etc. to pierce your
underground cable, conduit is not necessary. For 57 cents average cost /
foot, BURY-FLEX Tm is an excellent choice, above and below the ground. If it
seems cheap, it's only because we have an excellent direct relationship with
the factory that we chose to exclusively produce it for several years now.
Expect a 20-25 year life.
With ref to BURY-FLEX vs. insects: that spec may have been somewhat derived
from my spec that it is more rodent resistant and repellent than PVC. I'm
not an entomologist but I figure if my local beavers, squirrels, wood chucks,
etc., haven't caused me destruction of the PE, contrary to my PVC
experiences, then I doubt even termites have an interest in PE.
BURY-FLEX Tm has been one of our top 5 sellers. A good number of dealers
sell it. Our dealers are aware of the buriablity of various cables. If you
are not sure about a dealer, or if he is a cable expert touting buriable
RG213 because it has a "non-contaminating jacket, per the C-17 Mil Spec for
RG213, just bear in mind that "non-contaminating" has NOTHING to do with
buriability. Unless this dealer has a "modified" RG213 which uses PE vs. the
std. PVC on RG213, he's all wet, and so will your coax be. Cheers, Steve
Davis, K1PEK, DAVIS RF Co.
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DAVIS RF Co., commercial wire and cable, custom cable design. Discounts to
hams. Heliax, LMR, RFS, Belden, Poly Phaser Lightning Protection Devices.
Various aerial wiring; transmission lines and Dacron rope. www.davisRF.com .
1-800-328-4773, (For all RF hardline related items, please ask for Steve
Davis) Thank you! The Triad: Davis RF Co.; The WIreman, Inc and Orion
Wire Corporation.
In a message dated 4/2/99 12:58:19 PM Eastern Standard Time, w2xx@cloud9.net
writes:
<< Don't assume that just because a cable is marked
"Mil-Spec" that it is necessarily the best for your
application.
The direct-burial coax, such as that supplied by Davis RF
and The Wireman, can be buried without a conduit. The jacket
material is quite dense and should provide adequate protection
from most subterranean hazards. It is not armor plated, however,
and your average pick, shovel or backhoe will damage it easily
if you choose to dig in the wrong place in the future. >>
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