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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