Satgen 399 Antenna Rotators Pt4  by GM4IHJ   (BID SGEN399)  16 Nov 96

Continuing the discussion of antenna rotators versus the weather,
there are 3 main "enemies " - Wind , Water and Ice. Depending on your
station location you will get some or all of these , in varying
degrees of harshness. So perhaps IHJs location on a site where all are
present , can provide a set of, near worst case, examples.

WIND - Equinoctal gales each year ( March and late September) produce
wind gusting up to 150 kms/hr. Most commercial antennas give good
service in these conditions , so heavy duty types are not strictly
necessary . But rotators are a quite different matter and hard (
expensive) experience, has led to the adoption of only the most robust
of heavy duty rotators on all but the lightest of antenna masts.
Simple rotators are no good for the 10m beam , 6m beam or multiple 4
by 12 xy yagi array used for satellites. Local moon bouncer JJJ has
gone one better and employed a really robust rotator system for his 4
by 12 element 2m EME array. Recent events, where a hurricane off
eastern USA, turned east and hit Scotland, have firmly supported these
robust solutions.

WATER - is something that Scotland is certainly not short of. Most
radio amateur will be aware of the need to shield and protect rotators
and cables, with proven water proofing materials . But water can get
in the funniest places , as JJJ reports. In his case, his antenna
system self elevated to 90 degrees and would not move, after one
serious local copy, of an Indian monsoon, and it stuck there despite
full power on a sturdy elevation mechanism. The problem was water in
the antenna booms. Once the antenna elevated slightly in the breeze
the water went to the back end of the booms and the antenna went to 90
degrees. Do check that if water gets in, it can drain out.

ICE - warmed by the Gulf Stream, Scotland at 56N ( same as Hudsons
Bay) is generally free of deep freeze problems (unlike N America ).
But there is one meteorlogical sequence which can wreck any rotator,
whereby wet snow and persistent ice ,allowed to collect on the
antennas, can freeze solid overnight , turning you 10 Kg antenna into
a 100 Kg icicle. There is only one solution when this happens. Stop
operating and hope your antennas survive. Your rotator should not come
to too much harm provided you do not try to use it.

PS. From time to time you may hear of " new solutions " to the rotator
problem. Please beware. Some years ago a (non amateur radio) group,
inherited a large 10cm radar half cheese antenna, which they decided
to set up for radio astronomy experiments. Their solution to the
rotator problem was unique. They dug a pond 2ft deep and 12 ft each
side. They build a large raft of wood and pushed it into the empty
pond, then fixed the antenna firmly to the raft. After a simple
christening ceremony , they got a hose pipe and filled the pond ,
whilst holding the antenna in position with hand held ropes. At which
point the wind blew , the big cheese caught the wind beautiful, and
under full sail, sped for the adjacent bank against which it partially
capsized.Fortunally no bodies were damaged , but a few egos were.