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
> 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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