I would change the length of the feed line by 20 or so feet. Either add or
take away. I do hope the feed line is reasonably straight an if there is
any excess is not in a "coil" somewhere.
Also, are you using a 4:1 balun or a 1:1 balun? And are these voltage
baluns or current baluns? I find that 1:1 current baluns work better in
most cases unless one is feeding something like a folded dipole where the
impedance is close to 200 to 300 ohms. In this case a 4:1 works better.
Based on what you describe, I suspect that you are using a 4:1 balun. That
device doing it's job and presuming the load Z at the feed line at the
transmitter end is say 25 ohms then the 4:1 balun is making that look like
6.25 ohms. Most tuners have a problem with this. Therefore a 1:1 balun
would present a 25 ohm load to the tuner. Much better.
73
Bob, K4TAX
----- Original Message -----
From: "Phil Sussman" <psussman@pactor.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Wednesday, January 21, 2009 7:15 PM
Subject: [TenTec] Antenna question
This may be a bit off-topic - If so please forgive me:
I'm working with a fellow who has problems loading an 80M loop antenna
with
ladder line and a tuner. His antenna is about 380ft and I think that it's
a bit
short. I borrowed my Nye-Viking and the best that I can achieve is 3 to 1
match
at 3800 KHz.
At that point the tuner is applying MINIMUM capacitance. That makes me
think
that a longer antenna length is needed.
As an aside 40m loads no better 2.5 to 1, but 30m loads up OK.
If I take his balanced line and feed it as a long wire (one end
unterminated)
the system loads up just fine on 40m and 80m, but it is obviously
unbalanced.
Any quick hints appreciated -- I'm not the best with HF antennas.
PS. My 80m loop antenna is 420ft long and loads as balanced just fine.
de Phil - N8PS
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|