-----Original Message-----
>From: Tom Osborne <w7why@verizon.net>
>Sent: Jan 6, 2008 9:33 PM
>To: Towertalk <towertalk@contesting.com>
>Subject: Re: [TowerTalk] Phasing Question
>
>Jim Wrote:
>>
>
>>
>>
>> But.. in a multi element array, there's more to it than just the length of
>> the coax.. the elements interact with each other (mutual impedance), so
>> the feed point impedance of element 1 varies depending on what you're
>> feeding elements 2,3,4, etc. with.
>
>I asked this same question here a couple of months ago, and from what I
>received in answer, I assume unless you have a meter to detrmine inpedance,
>reactance, phase angles, vectors, etc, it is not worth doing to do it right.
That depends on what you mean by worth doing. If you don't get it right, all
that really happens is the beam points somewhere other than you expect AND you
lose some back and side attenuation (i.e. F/B gets worse). A lot of people
have put together casual systems and just flip the switch around the various
combinations to find the one that sounds best at the time.
If you have some specific performance goals, yes, you'll need some test
equipment and such.
>
>So, there is another question I have. If you just put up 1 vertical and put
>up another one 1/4 wave away, can you use this as a director or reflector by
>switching a coil in and out?
Sure. I think there's a two element Yagi that works this way, too. A relay and
inductor at the center of each element, and depending on which one has the
inductor, you can flip the direction 180 instantly. One can also do it with a
length of transmission line.
>
>This seems like it would be a lot easier to do. Thanks and 73
The tradeoff is in complexity, losses, and tunability. On the low bands, I'm
not sure a single inductor would work for the entire band, and once you go to
some sort of remote controlled inductor, the complexity compared to another
SteppIR is about the same.
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