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[TowerTalk] 75 ohm hardline/twinlead

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Subject: [TowerTalk] 75 ohm hardline/twinlead
Date: Wed, 29 Oct 1997 20:03:07 -0600
My personal rule of thumb is for runs of 200 ft or less, it is easier to
just use a good grade of 50 ohm cable.  With hardline, you will want
a flexible cable on each end which entails splices or extra connectors,
increasing cost and potential failures.

Ladderline requires insulating standoffs, is awkward to bring in the
house, and is susceptible to computer and other local noise sources.
It is nice for multiband operation of wire antennas.  Leave it off your
especially if you want to rotate that beam!

de  Tom  N4KG

On Wed, 29 Oct 1997 11:08:02 -0600 writes:
>Hi Bill.
>I imagine you will get responses from people who know more than I, but
>here are my thoughts (mostly just stuff I have heard/read over the
>> I have 2 questions:
>> I recently obtained some 75 ohm hardline from my cable company.  In
>> talking to the gentleman who gave it to me (and is also a ham with a
>> lot of antenna experience), I asked him about a means of matching 
>> 75 ohm hardline to the 50 ohm input  for my Icom 765.  His comment 
>> basically not to even bother or worry about it.....just hook it up 
>> go for it.  While he certainly seems to know what he is talking 
>> I am still curious as to whether this will work as easily as he says
>> it
>> will?
>I have heard that at HF it makes no difference, and also the type of
>splices and/or homemade connectors you might use also make no 
>at HF (as long as they are sufficiently protected against weather).  
>I also know that the purists like to use impedance transformers and
>"proper" connectors.
>> second question:  I have also heard (and wondered why not)  that
>> instead of using coax to feed    my beam, that I should just try  
>> ohm ladder line (I assume with a proper  balun of some kind) to feed
>> the beam and I should get real good results with minimum loss.  
>> I
>> am only going to have a short  run of about 60 feet to the beam, why
>> not use the ladder line instead of the more expensive coax?  It 
>> that I have only heard of a few stations that use this method,
>> everyone
>> else going with the standard coax.  Comments please!
>I think that ladderline could be used with good results, but there are
>some possible drawbacks.  First, ladderline might be desired for 
>long runs due to the low loss.  With your 60' run, any loss reduction
>would be negligible compared to decent coax, especially since you are
>using an antenna that probably presents a pretty good match to coax.
>Ladderline has to be routed carefully to keep it from coming too close
>to the tower or other conductors (getting it into the shack can also
>take some thought), and I've heard about needing to have a half-twist
>every few feet to keep the ladderline from radiating.  Also, rain/snow
>affects the impedance.  Dipoles fed with ladderline need an antenna
>tuner in the shack.  You don't want to have to adjust a tuner every 
>you change bands with your beam, do you?  I'm not sure if this would 
>needed or not if you use a balun at both the beginning and end of your
>feedline run.
>When I build a quad "some day" (I have had this cool aluminum spider
>mount for years!) I may try to feed it with ladderline to avoid having
>to switch in impedance tranforming stubs for each band.  We'll see.
>> Regards,   Bill - WX8S
>Dave WD5N  /  VP5EA
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