[TowerTalk] Temporary 160 meter antenna question

[Jim Brown]

On Fri, 4 Aug 2006 11:43:32 EDT, RLVZ at aol.com wrote:

>1) Load up a 80-m dipole on 160-m by running the RG-8  feedline through an 
>antenna tuner.  (unbalanced?)

I tried it in Chicago when I lived there, it worked VERY badly.

>2) Tie the rig end of the RG-8 coax together (center and shield tied  
>together) and run it through the antenna tuner.  The only ground available 
>for the antenna tuner/rig will be a couple of ground rods tied to the electric  
>meter which is 5' away from the rig.

I did this for a weekend contest, with a balun at the antenna. With 100W, I burned up the 
so-called KW-rated balun at the antenna (it turned into a dead short on the coax). Other 
than that, it got out better than option 1, but still not very well. 

A conventional dipole "choke" balun essentially adds a lot of resistance and reactance in 
serie with the coax at the feedpoint, so it means that the coax is the only part of the 
antenna that is working for you.  If there is no balun, it will work better, because the 
dipole acts as a "top hat" for the coax. And if you improve the counterpoise (the wires 
going to your ground rods are a counterpoise), it will work better yet. See 

http://audiosystemsgroup.com/K9YC/k9yc160TopLoad.htm

In your situation, I would go to Home Depot or equivalent and buy 1,000 ft of #18 copper 
and get as much of it connected as makeshift radials as possible. It isn't even terribly 
important WHERE they run, or even how long they are (although longer is better). An EARTH 
connection is more or less meaningless in this context, but the COUNTERPOISE is important 
(because it reduces the resistance of the return path for antenna current). 

73,

Jim K9YC