[TowerTalk] SteppIR interaction with 40m beam

[Joe Subich, W4TV]

On 2018-10-25 11:33 PM, W7ZZ wrote:

> If you make them 90 degrees to one another, then the boom of the
> Steppir could well interact with a 40 meter beam.

The boom of the SteppIR will *not* interact with a 40 meter antenna.
The SteppIR is only 1/4 wave on 40 meters and is *NOT* resonant.  In
order to couple to a yagi, an element needs to be close to 1/2 wave
long (+/- 20% or so - not - 50%)!

Take a little time to model a 1/4 wave element parallel to a 1/2 wave
element and look at the current in the 1//4 wave element - you will
find it to be zero or very close to it.

73,

    ... Joe, W4TV


On 2018-10-25 11:33 PM, W7ZZ wrote:
> I have a 4 element Steppir (traditional configuration, not trombone) at 70
> feet and a two element Cushcraft XM240 "shorty forty" above it at about 82
> feet.  I have experienced zero interaction except on 15 meters.  With the
> Steppir elements extended on 15, it was necessary to reconfigure and
> memorize a new configuration for the Steppir driven element on 15 to achieve
> the usual Steppir SWR of 1:1 or close to it.  Once I did that, 15m behavior
> was fine.
> 
>   
> 
> I did considerable research before putting this combo up in the air, and I
> drew the conclusion that a 12 foot separation was fine (more is better, but
> hard to do since the standard chrome moly pipe length is 22 feet and some of
> it needs to be inside the tower and 3 feet or so gets used for the 40m boom
> truss).  My booms are parallel to one another.  If you make them 90 degrees
> to one another, then the boom of the Steppir could well interact with a 40
> meter beam.  There is no need to do that, in my experience, and it
> complicates everything from construction to rotator control settings.
> 
>   
> 
> 73, Doug W7ZZ
> 
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