[TowerTalk] Heliax, Lmr, Bury-Flex Info & Conduit Pull Thrus
Jim
jdc@ieway.com
Mon, 13 Mar 2000 22:01:19 -0800
A standard 2 inch "sweep" (the ones you buy at Home Depot) are 10 or 12 in
sweeps.
It would be quite difficult to bend a 2 inch conduit into a 5 inch or less
sweep.
73
Jim W7RY
-----Original Message-----
From: DavisRFinc@aol.com <DavisRFinc@aol.com>
To: k3gm@home.com <k3gm@home.com>; towertalk@contesting.com
<towertalk@contesting.com>; n4zr@contesting.com <n4zr@contesting.com>;
K7LXC@aol.com <K7LXC@aol.com>; jonk@jskent.com <jonk@jskent.com>
Date: Monday, March 13, 2000 14:00
Subject: [TowerTalk] Heliax, Lmr, Bury-Flex Info & Conduit Pull Thrus
>
>
>Hi Tom,
>
> Andrews spec's this cable at a 5" bend radius. If the "sweep" you mention
>is good for this 5", which I doubt if it was not "overly" constructed with
>sweep joints, you will be exceeding that 5" min. spec which is not good.
>One problem with Heliax is that it requires greater bend radius than other
>cables of equal performance (some others are not as good attenuation at
>microwave though).
>
>The plus side of Heliax is its mechanical strength particularly as related
to
>its tensile and elongation ratings. This lends itself well to hoisting up
>large commercial towers.
>
>For ham use below 440 MHz, I have to be frank and say that the extra
>mechanical ruggedness of Heliax is not necessary and the attenuation
>improvement vs. LMR or "BURY-FLEX" Tm is minimal at best (unless we're
talkin
>very low power at above 230- MHz). The premium you pay for the Andrew name
>and the extra mechanicals (not to mention connector expense) is
considerable.
> You also deal with higher bend radius as noted.
>
>The 4 bends you mention are no problem if IAW the 5" spec.
>
>Direct burial is not a problem, another plus of the mechanical
construction.
>Not only is the PE (polyethylene) outer jacket a must, the shield below it
is
>a copper conduit, thus "vapor transfer" of moisture is inhibited. Also,
>this conduit type construction lends itself to protection of the inner
>dielectric and center conductor ref. possible vulnerability to an errant
>sharp spade shovel, etc. as your wife or significant other is in the "red
>zone" trying to plant flowers or whatever.
>
>So, without further data, which I'd be glad to go over with you in a
direct
>email, I'd say, "If no 5" min radius, direct bury it. If you have a
muscle
>bound "significant other" who likes digging holes, put it in a conduit and
>find her a field she's safe in.
>
>I sell all three of the above mentioned cables and connectors at the lowest
>pricing I'm aware of so it doesn't matter to me. However, I will ask any
>customer what the application is and advise as noted above. That's only
>ethical.
>
>By the way, the idea of vacuum suction of a string thru PVC is a good one.
>Just don't do what a guy did: Make sure if you use light weight yarn,
that
>the other end isn't attached to a SIP (sweater in progress). Turned that
>sweater into a neat "tank top" in 2 seconds. Cheers, Steve Davis, K1PEK
>DAVIS RF Co.
>note: comparison to lmr 600, .590" OD, not lmr500, .500". price
comparison:
>4-50A: 1.79/ft vs. $1.13 dir. bury lmr600db (or .98/ft std.) LDF 4 atten.
@
>450 MHz=.21 dB nom. improvement; @ 30 MHz=.16 dB (100')
>---------------------------------------------------------------------------
---
>-------------------
>DAVIS RF Co., commercial wire and cable, custom cable design. Discounts to
>hams. Heliax, LMR, RFS, Belden, BURY-FLEX Tm. Various aerial wiring; wire
>aerial parts; transmission lines, insulators, baluns, RF connectors 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.; Orion Wire Corp.; and The Wire Man, Inc.:
>Variegated expertise; resources and buying power yielding numerous quality
>products at highly competitive pricing.
>
>~ Davis RF Co., Div. of Davis Associates Wire and Cable, LLC:
>Distribution to numerous industries, Price Leader in Andrew Heliax and
>Times Microwave LMR Tm and others.
> peripherals. www.davisRF.com
>
> Tel: 1-800-328-4773 (1-800-DAVIS RF) Tech'l: 1-978-369-1738,
Fax:
> 1-978-369-3484
>
> ~ DAVIS/ORION Marine Wire and Cable Co., Distribution and
> Design:
>UL/USCG Marine Stds.
>
>~ Orion Wire Corp., Design Engineers of Specialty/Custom Cable
> Tel: 1-800-328-4773, 1-603-787-2200 Fax 1-603-787-2221,
> email: Orion@connriver.net
> www.davisRF.com
>
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