Hi Tom,
Sounds like the "professionals" who did these government installations were
unfamiliar with gravity.
RG17 and similarly constructed cables cannot be run vertically for any
distance without a clamped loop at the top of the run.
73 & happy holidays!
Steve WB2WIK/6
"If everything seems under control, you're just not going fast enough." -
Mario Andretti
> -----Original Message-----
> From: fclarke [SMTP:fclarke@erols.com]
> Sent: Thursday, December 26, 2002 7:27 PM
> To: Steve Katz
> Cc: 'k3bz@arrl.net'; 'Tom'; towertalk@contesting.com
> Subject: Re: [Towertalk] Coax
>
> Hi Steve,
>
> Thanks for the clarification! In the installations I referred to, the
> RG-17 was
> strapped to a 120 foot wooden pole with cable straps, so the gravity
> explanation
> seems right on. This was a professional (well, sort of, it was a
> government cable
> crew) installation. As the problem seemed to be common all over the
> base, the decision
> was made to replace all RG-17 with Andrews Heliax and the problem went
> away! Again, all
> the installations were vertical where the problem appeared.
>
> Thinking back on it, the horizontal runs (underground in conduit) to the
> HF Conical
> monopole antennas never had the problem. They still use -17, but are
> scheduled for
> replacement in the Spring, due to the relocation of the HF transmitter
> house.
>
> Tnx 73 de Tom/W4OKW
>
> Steve Katz wrote:
> >
> > Re: RG17...
> >
> > The center conductor doesn't shrink and withdraw the center pin. It,
> along
> > with the dielectric, can literally slide inside the braided outer
> conductor
> > and create the effect that you see, due to gravity and the incredible
> weight
> > of this cable.
> >
> > I've used it for 35 years and have never had this occur, even once,
> > following the prescribed instructions for use, which always include
> making a
> > drip loop at the antenna feedpoint and binding that loop tightly to the
> > tower leg or whatever's supporting the antenna. With a 360 degree loop
> in
> > place, the slippage cannot occur. This cable cannot self-support
> vertically
> > for any distance. If you use the same cable laying on the ground, you
> won't
> > see the "slippage" or "shrinkage."
> >
> > -WB2WIK/6
> >
> > "If everything seems under control, you're just not going fast enough."
> -
> > Mario Andretti
> >
> > > -----Original Message-----
> > > From: fclarke [SMTP:fclarke@erols.com]
> > > Sent: Tuesday, December 17, 2002 7:36 PM
> > > To: Steve Katz
> > > Cc: 'k3bz@arrl.net'; 'Tom'; towertalk@contesting.com
> > > Subject: Re: [Towertalk] Coax
> > >
> > > RG-17 has a nasty habit of the center conductor shrinking and
> > > withdrawing the center pin
> > > from the connector. Drove us nuts trying to troubleshoot a repeater
> > > problem a few years
> > > ago.
> > >
> > > Our base electronics shop canned all the RG-17 and replaced it with
> > > Andrews Heliax and
> > > solved many problems. Of course it is easy when Uncle Sam is paying
> for
> > > those $$$$$
> > > connectors!
> > >
> > > Hardline seems to be showing up at hamfests and then there is always
> the
> > > old standby -
> > > ex CATV hardline. 75 ohm, but there are ways around that.
> > >
> > > 73 de Tom/W4OKW
> > >
> > >
> > > Steve Katz wrote:
> > > >
> > > > Hi Jerry,
> > > >
> > > > I don't know anyplace in eastern PA, but if I lived there, I'll bet
> I'd
> > > find
> > > > one!
> > > >
> > > > Here in southern California, my usual source is Apex Electronics,
> 8909
> > > San
> > > > Fernando Road, Sun Valley, CA (818) 767-7202. They usually have
> miles
> > > of
> > > > it, still spooled, often with government contract tags still
> attached.
> > > >
> > > > Since 1000' of RG17A/U weighs about half a ton, it is expensive to
> ship.
> > > > When I lived back east, I always had a more "local" source of such
> > > items,
> > > > but that was a very long time ago. I'd probably do a search (Yellow
> > > Pages,
> > > > etc) on "military surplus" and "military surplus electronics,"
> "military
> > > > surplus wire and cable," etc. to determine who the local sources
> are.
> > > >
> > > > Also, if you live near any military depots, they usually have
> auctions
> > > > annually or so to dispose of stuff they don't need. I've attended
> such
> > > > auctions at Picatinny Arsenal in NJ and NWCC in Mechanicsburg, PA
> years
> > > ago
> > > > and the deals are absolutely amazing. One I remember is picking up
> a
> > > > 0-15Vdc, 0-100A regulated power supply (linear, and weighed about
> 200
> > > lbs)
> > > > for $50 in brand new condx. I couldn't lift it, so they helped me
> with
> > > a
> > > > pallet jack to get it into my station wagon...
> > > >
> > > > WB2WIK/6
> > > >
> > > > "If everything seems under control, you're just not going fast
> enough."
> > > -
> > > > Mario Andretti
> > > >
> > > > > -----Original Message-----
> > > > > From: Jerry Keller [SMTP:k3bz@arrl.net]
> > > > > Sent: Tuesday, December 17, 2002 9:10 AM
> > > > > To: Steve Katz; 'Tom'; towertalk@contesting.com
> > > > > Subject: RE: [Towertalk] Coax
> > > > >
> > > > > Steve... could you refer me to a source for that military
> RG-17A/U?
> > > I'm in
> > > > > eastern PA. Jerry K3BZ
> > > > >
> > > > > -----Original Message-----
> > > > > From: towertalk-admin@contesting.com
> > > > > [mailto:towertalk-admin@contesting.com]On Behalf Of Steve Katz
> > > > > Sent: Tuesday, December 17, 2002 10:40 AM
> > > > > To: 'Tom'; towertalk@contesting.com
> > > > > Subject: RE: [Towertalk] Coax
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > > I am getting ready to replace some 10 year old coax and was
> > > wondering
> > > > > > what the coax, not hardline, of choice is for HF now. It will
> be
> > > > > feeding
> > > > > > a 2 element
> > > > > > 5 band cubical quad with a capability of 1500 watts.
> > > > > >
> > > > > [Steve Katz] You didn't say how long that cable was going
> to
> > > be, or
> > > > > what is supporting the quad. The best choices for transmission
> line
> > > > > usually
> > > > > take into account the frequency of operation, line length and
> > > operating
> > > > > environment, e.g., fixed or crank-up tower; if any of the line
> will be
> > > > > buried; if any of the line will be inaccessible for service; etc.
> > > > > Example:
> > > > > For longer runs, my first choice is RG17A/U since it's very
> strong,
> > > very
> > > > > low
> > > > > loss and extremely easy to work with in all aspects except its
> rather
> > > > > enormous weight. So, I don't use it on crank-ups (too heavy), but
> for
> > > a
> > > > > fixed, guyed tower it's pretty perfect, not to mention readily
> > > available
> > > > > for
> > > > > a fraction of what the military pays for it. WB2WIK/6
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > > --
> > > > > > 73,
> > > > > >
> > > > > > Tom mailto:trobertson@elp.rr.com
> > > > > > KQ5S
> > > > > >
> > > > > >
> > > > > > _______________________________________________
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> > > > > _______________________________________________
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> > > > > See http://www.mscomputer.com
> > > > >
> > > > > Wireless Weather Stations now $349.95. Call Toll Free,
> > > > > 888-333-9041 for additional information.
> > > > > _______________________________________________
> > > > > Towertalk mailing list
> > > > > Towertalk@contesting.com
> > > > > http://lists.contesting.com/mailman/listinfo/towertalk
> > > > >
> > > > _______________________________________________
> > > > AN Wireless Self Supporting Towers at discounted prices,
> > > > See http://www.mscomputer.com
> > > >
> > > > Wireless Weather Stations now $349.95. Call Toll Free,
> > > > 888-333-9041 for additional information.
> > > > _______________________________________________
> > > > Towertalk mailing list
> > > > Towertalk@contesting.com
> > > > http://lists.contesting.com/mailman/listinfo/towertalk
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