Hi Con,
To: <towertalk@contesting.com>
> Date: Thursday, October 08, 1998 6:09 AM
> what happens if you connect a complex impedance (antenna) which is not
purely
> resistive but has a (capacitive or inductive) reactive component to the
> transformer?
If the transformer is perfect, the impedance is changed by the turns ratio
formulas you gave.
With a 100 ohm R and 100 X load through a perfect 4:1 transformer, the
complex impedance becomes 25 R and 25 X.
> how is this complex impedance transformed?
> example: if you connect an impedance of 100 + j50 ohms to a 1:2
transformer
> (high z side), what do you see on the low z side, 50 + j25 ohms??
Yes.
> the vector amount (sorry I dont know the proper word in english) of the
> complex impedance transformed?
Yes, that would also be true
> or do those tranformers only work "properly" with purely resistive loads?
> in the case with added reactance the tranforming ratio might depend on
> additional parameters like frequency and the way the tranformer has been
built
> (thus his own impedance..) ??
In the real world of less-than-perfect transformers, some modification of
the impedance other than an exact transformation will occur. You also will
have VAR power (called power factor or "Q"), which makes the apparent power
higher than the actual power because voltage and current are no longer in
phase.
In a well designed transformer that does a "good job" with a pure
resistance, it will do a good job with a complex impedance of the same
approximate value.
73 Tom
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