> From: "Sherrill WATKINS" <SEWATKINS@dgs.state.va.us>
To: <tentec@contesting.com>
> Date: Wed, 29 Mar 2000 10:20:54 -0500
> To: <tentec@contesting.com>, <jmlowman@ix.netcom.com>
> Subject: [TenTec] Re: Ten Tec antenna tuners>
>
> While I am a devoted fan of Ten Tec gear, I will not recommend their tuners
> as being the "best" design for use with open wire
> transmission lines. This is because it is my understanding that the design
> is a basic T type L C network. This is fine for
> unbalanced line but not balanced. The solution the factory uses is to place
> a balun in the output of the tuner. A much better method for feeding open
wire line is to place the balun on the input side of the T type tuner. Why
this simple solution never
> occured to the factory seems odd? However, I understand
> that there is one company that does make an antenna tuner with the balun on
> the input side, specifically for feeding open wire line.
Sir:
You are correct, there is, as far as I can survey, only one US
manufacturing company that places the balun (a 1:1 design) at the input of
the matching network where it can perform as it was intended: as a 50
ohm-to-50 ohm balance-to-unbalance transformation device.
The matching network I am referring to is the Palstar AT4K, manufactured
by Palstar of Ohio (see their website and this device at
<www.palstarinc.com>). All components following the balun are floating above
RF ground for use with the balun. However, I am told that, at the flip of a
lever, the device can be unbalanced for use with coax lines. I beta tested a
300-watt version of this network for the manufacturer a few years ago, using
my 80 meter center fed doublet fed with 450 ohm ladderline and it appeared
to provide a true balanced output on all bands up to and including 10
meters. It performed well on the air.
I have used several T-match networks with internal 4:1 balun over the
years and not one of them has provided a truely balanced output,
particularly progressing to the upper bands of 20-10 meters. The end result
typically has been rf flowing into one side of the balanced feeder,
resulting in a long wire antenna. No wonder so many have complained of RF in
the shack and RFI problems in the neighborhood.
Since there is no U.S.-based manufacturer currently producing
inherently balanced matching networks for the radio ham, the Palstar AT4K
might be a viable solution for those searching for a high power balanced
design. Take a look at the website for details on this device (the other
ATU's offered by Palstar do NOT, in my understanding, utilize the balun at
the input of the network).
Vince/K7NA
--
FAQ on WWW: http://www.contesting.com/tentecfaq.htm
Submissions: tentec@contesting.com
Administrative requests: tentec-REQUEST@contesting.com
Problems: owner-tentec@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|