Jim Brown wrote:
> On Wed, 22 Aug 2007 14:09:43 -0400, Tom Rauch wrote:
>
>> The other thing the amplifiers do is have a source impedance
>> of about 60 ohms or so to drive the 75 ohm cable. A
>> reasonable and stable (over frequency) output impedance is
>> necessary to maintain phase in the elements.
>
> YES! And this is NOT trivial! Phase shift in the resulting network
> (antenna through transformer to transmission line) will add to the
> delay of the transmission line. The resulting pattern will not be
> as expected.
>
> Jim Brown K9YC
I'm not an engineer and am having a hard time understanding this.
It's my understanding that, if a cable is terminated in it's
characteristic impedance, the phase shift will be equal to the
electrical line length regardless of source impedance. If this is
true, then the phase shift through the antenna matching system,
whether it be active or passive, would be irrelevant as long as
all were stable and equal.
73, Roger
--
Remember the USS Liberty (AGTR-5)
http://ussliberty.org/
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