---------------------- Forwarded by Tyler G Stewart/BENN/CEC on 10/30/97
08:41 AM ---------------------------
Tyler G Stewart
10/30/97 08:13 AM
To: wbh3@chrysler.com
cc:
Subject: Re: [TowerTalk] 75 ohm hardline/twinlead (Document link not
converted)
On part one, I would certainly try feeding your antenna without
transformers as long as it's a monobander. In this case, I'd use 75 ohm
coax for the pigtail to the antenna and 50 ohm in the shack to start. If
things dont look good, you can substitute lengths of 75 ohm coax in the
shack until you hit the magic combo that works well...usually the best
electrical length for this will be an odd quarter wavelength of feedline.
If you are planning on feeding more than one band with this coax, you wont
be able to play the transmission line matching game very well, so in that
case I'd use the broadband transformers. Amidon and ICE make good ones.
On the twin lead feed, unless you are talking about a wire beam out in the
open somewhere, it wont work. Balanced feeds
require at least symetrical disturbances to keep from radiating. If it's
on a rotating yagi on a tower, I dont see how you could accomplish this
feat.
73, Ty K3MM
wbh3@chrysler.com on 10/29/97 11:21:48 AM
To: towertalk@contesting.com
cc: (bcc: Tyler G Stewart/BENN/CEC)
Subject: [TowerTalk] 75 ohm hardline/twinlead
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 the
75 ohm hardline to the 50 ohm input for my Icom 765. His comment was
basically not to even bother or worry about it.....just hook it up and
go for it. While he certainly seems to know what he is talking about,
I am still curious as to whether this will work as easily as he says it
will?
second question: I have also heard (and wondered why not) that
instead of using coax to feed my beam, that I should just try 400
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. Since 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 seems
that I have only heard of a few stations that use this method, everyone
else going with the standard coax. Comments please!
Regards, Bill - WX8S
wbh3@chrysler.com
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