[TenTec] OT Antenna Tuners

[Dr. Gerald N. Johnson]

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