[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

It would be quite difficult to bend a 2 inch conduit into a 5 inch or less

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
>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
>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
> 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
>Not only is the PE (polyethylene) outer jacket a must, the shield below it
>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
>email, I'd say,  "If no 5" min radius, direct bury it.  If you have a
>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
>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,
>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
>note:  comparison to lmr 600, .590" OD, not lmr500, .500".  price
>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
>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,
> 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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