[amsat-bb] Re: [amsat-dc] Re: inquiry about homebrew az-el systems (Samudra Haque)

Stephan Greene ks1g04 at gmail.com
Mon Feb 25 17:47:14 PST 2013

Two additional points, speaking as someone who's mechanical fabrication &
coding skills are equally lacking (downside of systems engineering is you
understand the functional flows, associated diagrams, requirements
boundaries, etc. quite well, but need a bit more than a book of "the system
shall..." statements to accomplish anything!).

The WA5VJB "Cheap Yagi" designs are ridiculously easy to build [the most
complex tool is a guide to keep a hand drill perpendicular if you lack a
drill press]; given the relatively lower gain required for LEO satellites,
it would cheap & easy to build a higher-gain version of the Arrow (I am
1/2-way there) or pairs of LHCP and RHCP antennas and switch to one or the
other rather that at the phasing harness level.  They are not as-is rugged
enough for permanent installation, but I think the design could be
adapted.  There is a DK-something in Germany who has published a wealth of
high-performance designs that are suitable for permanent installation if
you select the right components.   In emails with WA5VJB, he mentioned to
me that the performance of the Arrow is very suboptimal.  That's one reason
why smaller (fewer elements) designs often outperform the Arrow. [Not that
I dislike the Arrow, I have one & it works.]  I think he's discussed this
in CQ Magazine or CQ-VHF.

It is a tempting design project to acquire surplus drive motors and
fabricate a mechanical system and remote/computer control (and I'm semi
surprised the VHF/UHF rover community hasn't done more with this), and it
is something I'd like to do myself; I'll note however that the Yaesu az/el
rotor controller draws very little power - a small inverter was sufficient
to run mine for Field Day last year.  Further, Bob Brunginga (WA4APR) has
noted that an azimuth-only station can be quite sufficient for at least
getting started with LEO satellites.  Something to keep in mind, depending
where the resource budget falls in terms of manpower vs. money.
Historically, AMSAT has opted for the people time are cheaper than dollars.

I look forward to seeing what you find out, Samudra, and hope you are able
to attend the DC portable satellite meeting the end of March.

Steve KS1G

Steve Greene  ks1g04 at gmail.com  <kay ess one gee zero four>@gmail.com

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