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Re: [TowerTalk] SteppIR

To: Towertalk <>
Subject: Re: [TowerTalk] SteppIR
From: Bob Nielsen <>
Date: Wed, 18 Feb 2004 17:42:20 -0800
List-post: <>
On Wed, Feb 18, 2004 at 09:37:42PM -0000, Jim Jarvis wrote:
> Al,
> I own a 3 el. SteppIR.  Went through exactly the selection process
> you're experiencing now.  Some thoughts:
> * Fixed element spacing can be accomodated, to some degree, by
>       element tuning.  The antenna gives you a reasonable half-power
>       beam width, and good f/b on all frequencies, 20-10.  I doubt
>       that any beam on similar boom length will beat the SteppIR
> * A 3 element monobander...or 3-3 element monobanders on a common boom,
>       like the current crop of 'tribanders', will likely equal the
>       SteppIR.  EXCEPT that the vswr bandwidth may not be where you
>       want them, and may require iterative tweaking to get them where you
>       want them.  With the SteppIR, you just put it up and tune it from
>       inside.
> * Stepper motors are highly reliable.  Ask fluid motion about crash
>       parts, if a tree attacks the antenna.  you'll find they're reasonable.
> * They have no 30/40m solution, except for the bigIR vertical.  I've been
>       thinking of a CC 40, with 2 30m elements inside it, on the same
>       boom.  SteppIR appears to be limited by the size of the molded motor
>       housing.  They can't accomodate bigger spools without tooling a new
>       housing.  I'd love it if they did.  2 els on a 24' boom would be ideal.

I can think of a number of possible ways to accomplish this:

1.  Two BigIRs back to back for each element.  This might get expensive
as it would require 2 stepper motors on each element.

2.  A fixed element (either aluminum or fiberglass with copper tape)
with a stepper motor and variable-length tape at the ends to tune from
7 - 10.1 MHz.  The control wires could run inside the tubing.  With the
larger spacing required for 30/40, it wouldn't be practical to use it
over 40-6 meters anyway.

3.  A single stepper motor, as in the current SteppIR, but with
elements which only partially retract, allowing the spool to fit the
current housing.

Bob, N7XY


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