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Re: [TenTec] OT Antenna Tuners

To: tentec@contesting.com
Subject: Re: [TenTec] OT Antenna Tuners
From: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Reply-to: geraldj@storm.weather.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Tue, 22 Jul 2008 09:08:52 -0600
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
On Tue, 2008-07-22 at 14:48 +0800, Marinus Loewensteijn wrote:
> I have not been following the thread closely. However I disagree with the 
> statement that the 
> input unun is "just" a transformer. It is important that is understood that 
> this is an unun where 
> there is very tight coupling between input and output.

EXACTLY the definition of just a transformer. Only the frequency range
is different from the power transformer out on the power pole. Gives
that 1:4 impedance ratio (1:2 voltage ratio) over a wide range of
frequencies without introducing significant reactance to the circuit.
Its a very predictable and useful component, but its just a transformer,
not a un or unun or balun, just an impedance transformer.

> Otherwise one gets a shunt L and a series 
> L and that will translate the setup into a low pass T-match which will not 
> perform with the same 
> advantages. Similarly it is not an old fashioned link coupling. In the latter 
> case the coupling is 
> loose and the secondary is a tuned circuit.
> Above 21 MHz the stray capacitance becomes noticeable and together with the 
> (for the higher 
> frequencies) rather large steps of the toroid - switch (combined in one item) 
> limit the matching
> capabilities. 
> I am more than happy with the performance of this ATU for coax : coax 
> matching. It is serving
> me FB.
> 73, Marinus, Zl2ML
73, Jerry, K0CQ

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