[TowerTalk] Coax RG393/u

[Jim Thomson]

Date: Sun, 14 Nov 2010 21:34:40 +0000
From: "K1TTT" <K1TTT at 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 at i5nph.net]
> Sent: Sunday, November 14, 2010 20:37
> To: TOWERTALK at 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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