[TowerTalk] Delta Loop Info and Opinions?

[Joe Giacobello]

Tom, thanks again, and it's interesting you brought up the issue of the 
balun on the input of an unbalanced tuner.  I have some comments about 
that, but I'm going out of town very early tomorrow (Ivan permitting) 
and will get back to you when I return. BTW, I had some correspondence 
with W7EL on the subject and (I think) I copied you.

Will be back to you later.

73 and thanks for help!

Joe

Tom Rauch wrote:

>>Tom, thanks for your reply.  In all honesty when I read
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>the article, it
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>>made sense to me because if one were trying to minimize
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>the interaction
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>>between the delta and the tower, minimizing the RF current
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>flow on the
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>>tower seemed logical.  I went back and rechecked the
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>article to make
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>>sure I hadn't gotten it backwards, and I hadn't.  I am
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>going to have to
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>>reconsider the whole issue in light of your explanation.
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>
>I have something on my webpage at:
>
>http://www.w8ji.com/detuning_towers.htm
>
>Basically the drop forms a parallel tuned circuit that
>isolates the section. When you measure the cirrect in the
>drop wire, which is what I believe the book suggests, if you
>set the shunt wire current to zero the shunt wire has NO
>effect!!!
>
>Going from the top of a structure to ground, or if the tower
>is long in terms of 1/4 wl sections, the results are
>different. In that case the only reliable way to detune is
>to measure the overall effect of the structure on pattern or
>re-radiation with a FS meter.
>
>Anyone who has worked with resonant systems knows the
>circulating current is maximum when the system is resonant.
>For example a trap isolating two sections of an antenna has
>maximum current circulating in the trap when the loop
>through the inductor and capacitor forming the trap has
>highest current!
>
>Intuitively, as another example, people think moving a balun
>to the input of a floating network makes balance better and
>reduces balun heating. That isn't correct, yet everyone
>believes it. This is why we have to take everything we read
>with a bit of caution, and not go by first instinct.
>
>  
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>>BTW, I did mention that the deltas were for 30 and 40M and
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>I had planned
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>>on vertically polarizing them and feeding them with
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>balanced line.  The
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>>reasons for using the loops are that I am looking for some
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>gain and
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>>directionality on 30 and 40M with a low takeoff angle,
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>simplicity and I
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>>have a lot of experience with quad loops.
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>
>Must have missed that. Loops reduce height requirements, and
>that's a good thing. Just be careful with the feedline. The
>feedline can be more of a worry to decouple than the tower
>supporting the loop.
>
>I'd install it first, and worry about problems later if they
>show up.
>
>73 Tom
>
>
>_______________________________________________
>
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