Date: Sun, 14 Nov 2010 21:34:40 +0000
From: "K1TTT" <K1TTT@ARRL.NET>
Subject: Re: [TowerTalk] Coax RG393/u
It looks like it should be usable outside, but seems kind of expensive and
lossy.
David Robbins K1TTT
> -----Original Message-----
> From: Natale Borghetti [mailto:i5nph@i5nph.net]
> Sent: Sunday, November 14, 2010 20:37
> To: TOWERTALK@contesting.com
> Subject: [TowerTalk] Coax RG393/u
>
> I would like to know if coax RG393/U could be used outdoor ??
>
> 73
>
> Natale
> i5nph
### RG-393 works great outdoors. It has slightly better loss than
RG-213U on HF. IF your requirement is for rotor loops that will
handle 10-25 kw, and swr, and has to be flexible, then RG-393
is the ideal coax for the job. The RG-393 rotor loops can be
spliced back into more rigid coax, like 7/8" heliax...for the trip
down the tower. At the junction point between the RG-393 and
the bigger coax is an ideal place to ground the bulk head connector
to the top of the tower. Then the braid'S are dc grnded to the tower.
## IF one plans high power operation, use 7-16 Din connector's. If you
require
a bead balun that will handle 10-25 kw, then slide 17-24 x large type
43 beads over the RG-393..right at the feedpoint. These are the beads
that are 1" OD x .515" ID x 1.125" long. Then put heatshrink over the
beads. That will work from 7-60 mhz. If it's for 80m band, you need at
least
24 x beads. If it's for 160m, you need at least 30-36 x beads.
## I would recommend Dow Corning DC-4 grease on all the 7-16 din threads,
and also the center pin. Torque the connector's down correctly, and use
vapour
wrap, 88 tape and then heat shrink.
## There is very little flexible coax around, that will handle high power.
For
short to medium runs, RG-393 is ideal. It's OD is aprx .390" [ vs .405" for
213-U]
It's superb coax for high power bead baluns, using type 43 beads, with the
provisio
that you use lots of beads. You can also use a type 31 torroid choke balun
downsteam
to supplement the bead balun. A 3rd choke can be used on the output of the
amp.
## Steve davis has the best prices on RG-393 bar none. He also has the
correct crimping
tool + the crimp style 7-16 Dins for the RG-393. The crimp version is easier
to install on
RG-393 /RG-214.... since both have a double braid, which is a bitch to comb
out.
## On any rotating tower setup, rigid heliax can be used going up the tower,
and also
along each boom. The 'rotor' loop coming off the base of the tower has to be
flexible though.
The RFS brand heliax in the 7/8" and 1.25" versions is now available with
a
corrugated CU center conductor..which makes it very flexible.... vs the Andrew
version..with it's rigid CU inner tube. The 7/8" version is aprx $2.35 per
foot [with
a corrugated inner and outer conductor]. It's even less if the Corrugated AL
outer conductor and corrugated CU inner conductor version is bought. Davis
RF
has both types, plus the 7-16 dins for both types.
Later... Jim VE7RF
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