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[TowerTalk] Antenna feed methods?

To: TOWERTALK@CONTESTING.COM
Subject: [TowerTalk] Antenna feed methods?
From: steve d <kc8qvo@yahoo.com>
Date: Tue, 3 Jul 2007 10:24:58 -0700 (PDT)
List-post: <mailto:towertalk@contesting.com>
I am going to be in Canada in a bit over a week and will be taking my radios 
along. Its mostly a VHF operation though - the grid is EN39, so if you are a 
grid hunter then look me up on QRZ.

Anyway, I am going to use 40 and 20 for my contact frequencies. In past years I 
have used a screwdriver antenna for general HF fun, but its a compromise. Its 
pretty short and has lots of loading on the lower bands. So this year I would 
like to use a vertical. I am going to use about 48' of military tent poles as 
the pole. 

Now comes the question: What is the best way to feed this through a tuner to 
get multiband coverage? 

I set one like this up at field day (shorter, though) and worked everything I 
heard and loaded it up on all bands 160-15 (I dont think I tried anything 
higher). I fed it with ladder line to a T-tuner with an interna 4:1 balun. 

Since this is going to be used on multiple bands I dont want to use coax. The 
antenna is not going to present a 50z match to the line. If I get up to about 
3db of transmission line losses I will loose half my signal. 

Ballanced line doesnt have the same loss properties as coax when presented with 
a wide range of impedances, thats why I would like to use it. I also have a 
tuner that will work with it (palstar at1500cv). 

There are a few issues with running the line though - how do I get it inside 
the cabin?
I could run it under the back door (along with all my other lines). This is the 
easiest method, but the door has a 4-6" wide metal plate on the floor with a 
rubber seal on it. The metal will interfere with the ballanced line. Unless 
that short of a distance wont matter much?
I could do the same thing, only use two runs of coax through the door jam.
I could also use coax to run from inside at the tuner to a balun outside, then 
ladder line from there.
Or I could run two parallel lines of coax as ballanced line to the antenna. 
However, from what I have heard this doesnt make much sense - the loss through 
the coax would be the same as if it were run in one line.
Another option would be to run some metal rods through the log walls, like the 
brass tubes you get at the hobby shop, and connect my ballanced line on to 
that. I dont know how possible this will be until I get there, though. 

What do you guys think? How can I minimize losses here?

I know the best route would be a signle band antenna, but that would only get 
me on one band. 
   
  Steve, KC8QVO

       
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