[TenTec] Tuner for Centurion to balanced antenna

["Rob Atkinson, K5UJ" <k5uj@hotmail.com>]

First, forget about setting up something for your centurion.  You want a 
system that can handle any amp up to at least 1.5 kw but preferably around 2 
kw just for some margin for error, heating etc.

If you fix it  to handle at most 1.2 kw, next thing you know, in a few 
years, you may have a titan III or something, and have to redo the antenna 
system to handle it.  set it up to handle legal limit now, and you never 
have to worry about it again.

I don't know how much room you have.  If you can't put up a horiz. loop for 
80 to 10, then you want two center fed zepps, one for 80 to 30, and the 
other one for 20 to 10, i.e. one 1/2 w. for 80 and one 1/2 w. for 20.  Feed 
each with open wire feed.  Make or buy a balanced transmatch.  Forget the 
238.  Palstar makes a bal. transmatch that is supposed to be pretty good.   
any balun you use, either coaxial or bead balun should be on the low z side 
of the xmatch where the z should always be 50 ohms no reactace because the 
xmatch is (hopefully) always tuned right, so ur balun will be 1:1.   you 
want to separate the two zepps so they don't interact.  Or, you can make the 
10 to 20 meter one vertical. and the low band one horiz.

The key is bal. feed; forget coax to the ant. feedpoints.  with bal. feed 
you have no worries about ant. resonance, swr heating, swr related loss, 
etc.  Bring the ladderline inside just enough to get it inside; put the 
tuner up near the entrance, then coax (good stuff like belden 238) the rest 
of the way to the rig.  if you have to remote the tuner you can get the 
Bliss Matchmaster which is a balanced xmatch that is remote controlled but 
it's pretty expensive.  either way, you have to have a true balanced 
transmatch, the other key element in the system.

But let me tell you, once you get the wires up, the feed routed, and the 
gear in place, it will be worth it.  everything will tune like a dream, the 
efficiency will be way up there, low noise, ur rig will be happy as it will 
always see a near 50 ohm load and you will wish you did this years ago.
Two || wire feeds?   Outside at the entrance, cut the feed and terminate it 
with bananna sockets.  put banana plugs on the parallel feed line ends.   
which ever one you want to use, just plug into the outside sockets mounted 
flush with the wall (or window).   you will want this anyway as a quick 
disconnect for ur ant. when there is lightning.

rob/k5uj

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