Augusto Yipmantin wrote:
> The motor speed gives me one turn of the antenna each two minutes.
> What I need is one turn in 5 minutes.
> This will give me more precision pointing the antenna, the reduction of
> the velocity never can be variable, it must be fixed.
>=20
> The rotor is a CDE Ham IV, and has some gears to reduce the motor=B4s
> velocity.

Might I ask what kind of antenna you're turning that you need the
additional accuracy?

I've used many a Hav IV or similar rotor and have never had a problem
stopping the antenna in a relatively good position for the station I'm
working.

Yaesu rotors for both Azimuth and Elevation under computer control are
used for things like Satellite tracking contacts (people also do this by
hand with hand-held antennas and a little practice).

But the only application I can think of where accuracy really gets
tricky is in the frequencies above UHF.  In that case, I've seen people
go to extremes to get more accuracy for dish antennas, etc.

Usually the problem is not the rotor speed, it's the rotor's accuracy.
Many can only move at a minimum by 1 to 2 degrees.  When doing
long-distance weak-signal work in the GHz ranges, with extremely
high-gain dish antennas, or enormous Yagi arrays, you regularly need 1/2
a degree of accuracy.  Some VHF/UHF contesters turn the entire tower
with a motor and chain, or in the case of one group, old WWII-era
aircraft propeller prop pitch assemblies, which can be very accurate and
 very strong to turn entire towers with their antennas bolted to them in
accurately fixed arrays.

But in general, that is one of the only Ham applications I can think of
where that type of accuracy is necessary.  The beamwidth of the main
lobe of your antenna is likely to be plenty wide for any but the most
sloppy rotators.

Heck, in contests and things I've worked 1/2 hour to an hour off the
BACK of the Yagi, and didn't have to turn the antennas around.

(The most fun this year was working contacts via the auroral curtain
during the ARRL VHF QSO Party in June.  Point the antenna anywhere
within 30 degrees of north and work people thousands of miles away on 50
MHz with only 100W.  What fun!  It's rare to have big aurora openings on
6m like that, and this one lasted at my location for almost 4 hours and
accounted for a huge number of points for grids we normally would NEVER
 work from DN70!)

So... I'm curious.  What are you aiming that requires such accuracy with
a Ham rotor?

Nate WY0X
--=20
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