DID TEURS

Marion D. Kitchem K4COK
7100 Mercury A ve.
Haymarket VA 21069
Rotator Rescue Mission
- prevents sudden stops
It was not too long after
in stalling the new a ntenna
and the Ham II rotator
that it happened: The tnbander
and two-meter
beams were at top rotation
speed when my finger
slipped off the brake release
lever. There was a
loud noise that came down
the tower, rippled with a
chill up and down my backbone,
and finally settled in
my hip (wa ll et) pocket.
Maybe omitting those torsion
bars on the guy wires
was a mistake. I had visions
of many small broken parts
scattered inside the rotator.
But the Ham II is pretty well
made; it all stayed together
without breaking.
Since that day, special
care was taken to be sure
that the a ntenna was at a
complete stop before releasing
the brake lever.
Then in the heat of trying to
catch that six-meter statio n
in Utah, the wrong lever
was released first, again at
top rotation speed. luckily,
all stayed together again.
At this point it became
obvious that so me ham
Photo A. Added refa y with components o n perfboard cemented to case.
might come along who did
not know how to o perate
this equipment and could
cause substantial damage!
Protection was needed to
prevent release of the brake
while the antenna was rotating.
If a relay was added
that released th e brake
when either rotate lever
was depressed, this same relay
could be made to delay
re lease of the brake until
the antenna had stopped
turning. This approach to
the problem was incorporated
in a Ham II rotator
and is presented here for
those who would like to do
the same. Note that singlelever
(instead of two)operation
is achieved with this arrangement.
This addition to the Ham
II is a very simple c ircuit. It
uses easy-to-find parts and
readily accepts substitutes
from your junk box. Normal
operation of the rotator is
not affected; you can still
use the brake and rotate
levers as the factory inte nded.
On gusty, windy days, it
is conven ient to use the
manual brake release until
the antenna has stopped
being blown about. Wait
for the direction indicator
to show a lull, and then release
the brake lever. The
brake release time delay
can be adjusted to suit your
particular antenna installa·
74 73 Magazine . April, 1981