Add-on to Rob's post: BE CAREFUL WITH PALSTAR!
Indeed Palstar now makes a box or two that is truly symmetrical, but a few
years back they had two boxes which were not symmetrical, yet advertised
them as being good for symmetrical wire. NOT. I bought the more expensive
one and soon threw it out. (Both had a balun on the TX side)
If I'm not mistaken, the ones which are truly symmetrical (or balanced) now
have the letters "bal" in their names. Still, buyer beware. Do your own
due diligence.
73
Rick
-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of Rob Atkinson, K5UJ
Sent: Tuesday, July 19, 2005 9:07 AM
To: tentec@contesting.com
Subject: [TenTec] Tuner for Centurion to balanced antenna
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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