[TowerTalk] Flaky dipole

[Grant Saviers]

It is the water or dirt on the PE web which causes the increased loss.  
Way back, when UHF first was broadcast (remember the external 
tuner/downconvertor boxes?) , there was a version of 300 ohm twin lead 
that was encased in foam and then a PE jacket so the weather didn't 
affect it as much, or with proximity to other materials.  I think 
another version had a hollow tube between the conductors.  I haven't 
seen that for a long time.

If 93ohm coax is used then 186 ohm balanced feeders can be made. There 
used to be a lot of cheap RG62 around from earlier computer systems, not 
so much any more. I think most is CCS center conductor same as a lot of RG6.

Grant KZ1W



On 8/2/2016 9:31 AM, Jim Thomson wrote:
> From: Grant Saviers <grants2 at pacbell.net>
> To: Tom Osborne <w7why at frontier.com>, towertalk at contesting.com
> Subject: Re: [TowerTalk] Flaky dipole
>
>
> First, I have to admit to a strongly held opinion that "ladder line" is
> one of the worst feedlines one can chose for getting the rf to the
> antenna.  By "ladder line" I mean the windowed polyethylene insulated
> "twin lead". The "low loss" mystique is misleading.
>
> Yes, it is low loss when suspended in free space in a vacuum.  If it is
> wet or dirty or in contact with most anything the loss goes WAY up.
> see  http://www.k6mhe.com/n7ws/Ladder_Line.pdf   and
> http://www.karinya.net/g3txq/wet_ll/
>
> ## can u get the  300/450 ohm line..without the windows ??
> Seems to me that 300 ohm TV type line back in the 60s /70s
> had no windows, I remember it well.  It was also available
> in a windowed variety.
>
> ##  along the same subject, back in the 70s, solid twinlead
> was available in 75 ohm.  Came in 2 x formats, small and large.
> The large stuff would easily handle high power.   Back then,
> the kw rated 75 ohm twinlead was fed  directly to the dipole,
> then the other end had a PL-259 installed on it.   Dunno if its
> still available or not.   With no windows in the line, water wont collect.
>
> ##  On a similar note, a buddy used paralleled 50 ohm coax,
> to make  100 ohm, shield, balanced line for his quad project.
> Shield tied together at each end.  100 ohm Z between the
> 2 x center conductors.   Made from 2 x 213-U  taped together
> every few inchs.  Can also be done with 2 x RG11  to make
> 150 ohm, balanced, shielded line.
>
> Jim   VE7RF
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