Many years ago I used a car windscreen wiper motor and gearbox to do
just this. IRRC the boom was monted in two ball races and there was an
operating arm , set at 45 degrees to the main polarisation, which was
attached to the wiper motor and the boom. Sorry but I really can't
remember any further details but ISTR that I had to make the motor
operate in "one wipe" mode by frigging the switch.
hth and seasons wotzits, Mike W, G8NXD
--
On Tue, 23 Dec 2003 10:24:12 -0000, "Richard"
wrote:

Hi. Has anyone designed a way to mechanically rotate their VHF/UHF yagi so
that it can be either horizontally or vertically polarized? If so, can you
please direct me to a website or whatever. Preference right now for a
manual system, but would also take a look at motorised systems.

TIA.

Rich.

(Followup set to rec.radio.amateur.antenna, so all replies will go to this
group).