[Antennas] Re: Removing the inner from coax.

Sat, 23 Aug 2003 18:20:25 -0500

Black poly tubing, such as sold in coils for water irrigation, has
outstanding weather and UV resistance and is very light and tuff.
If holes be drilled slightly smaller than the wire(+insulation) diameter,
V shaped notches can be cut into the holes from the ends.
This being done, the wire can be press snapped into the hole cold from
the outside.   The insulator will hold tight to the wire
by simple common friction.   This method allows stranded, insulated, and
more flexable wire to be used for the feedline and the parallel
wires to be stretched out first and the spreaders "snapped" on after at
fixed intervals.  Have yet to find a method or material that beats
the above.   Fiberglas will fray and deteriate at the cut ends and
drilled holes and is heavy.   Not so with the black HDPE tubing.
73 de Mike, AC5P

On Fri, 22 Aug 2003 23:23:07 -0700 "Chris BONDE" <[email protected]> writes:
> Barry:
> 
> Some questions on the fibreglass.
> 
> Drilling with carbide bits suggest cutting with carbide blades, 
> True?
> 
> How can they be joined together to form a long whip etc? 
> 
> One suggestion for the plastic spreaders was to heat the wire at 
> point of contact with 
> spreader and wire taut, it will melt its way into the spreader and 
> close the gap 
> behind it.  Anything similar with the fibreglass (solvent?)?
> 
> Chris opr VE7HCB
> 
> From:                   "Barry L. Ornitz" <[email protected]>
> To:                     <[email protected]>
> Subject:                [Antennas] Re: Removing the inner from 
> coax.
> Date sent:              Fri, 22 Aug 2003 20:19:24 -0400
> 
> >> Polyethylene, the plastic material used for the coax 
> > dielectric, has no ultraviolet resistance.  Used outdoors, it 
> > will quickly break down and eventually crumble.  Long before 
> > this happens, the surface will become crazed with small cracks 
> > which hold dirt and moisture and make it quite lossy.
> > 
> > Dave, W9LYA, suggested the use of small diameter PVC 
> > (polyvinyl chloride) pipe instead.  While PVC is not a 
> > particularly good dielectric at radio frequencies, it will 
> > work well in this application if you are talking about 
> > relatively wide spacings (2.5 cm, 1 inch, or more).  The rigid 
> > pipe will hold up far better outdoors than the soft PVC clear 
> > tubing.  There are several reasons for this: first the rigid 
> > pipe has white or black fillers that will refelct or absorb, 
> > respectively, the ultraviolet light that does the damage, and 
> > second, the soft tubing contains considerable amounts of 
> > plasticizer (often over 50%) to make it soft.  Most 
> > plasticizers will eventually leach out of the vinyl, and all 
> > have poor dielectric properties at radio frequencies.
> > 
> > Chlorinated polyvinyl chloride, CPVC, pipe is also available.  
> > It has a higher heat resistance, better chemical 
> > resistance, and is somewhat less flammable.  Its low frequency 
> > electrical properties are similar to rigid PVC but it has less 
> > ultraviolet resistance.  The dielectric properties of CPVC at 
> > RF are worse than rigid PVC.
> > 
> > Recently I ran across another item that should work well in 
> > this application.  I found fiberglass rods at the local farm 
> > supply store that are used for temporary electric fences.  
> > These rods are about a half inch in diameter (12 mm), and 
> > about three feet long (slightly shorter than 1 m).  They are 
> > very strong and rigid.  Being glass filled, they will wear out 
> > steel drills in short order, but they can be drilled with a 
> > carbide bit easily.  They cost about $1 each.  As spreaders 
> > and insulators, they should last quite a while outdoors.  A 
> > coat of acrylic paint, such as Krylon, will waterproof them 
> > and provide even longer ultraviolet protection.
> > 
> >         73,  Dr. Barry L. Ornitz     WA4VZQ     [email protected]
> > 
> > - - - 
> >
> 
> 
> - - - 
> 
> Your moderator for this list is:
> Larry Wilson KE1HZ [email protected]
> _______________________________________________
> Antennas mailing list
> [email protected]
> http://mailman.qth.net/mailman/listinfo/antennas
> 
> 