Re: tilt angle of TVRO dishes terrestrial 13cm use


Dave (G1OGY)
 

On Wed, 14 Apr 2021 at 22:51, G0FVI via groups.io
<Andrew.gilfillan=ntlworld.com@groups.io> wrote:

Quick (and possibly daft!) question (still learning as far as uwaves go). Going to venture out /P for first time soon on 13cm terrestrial. I will be trying an 85cm offset TVRO dish which I have used to demo AO100 at local clubs. I take it for terrestrial use the dish needs to tilted downwards from zero degrees? (it has the tilt bracket marked in degrees on rear and can be reverse mounted to allow downward tilt).

Hello Andy

FWIW I recommend mounting the dish "horizontally".
With a round off-set dish you should find that your `bore-sight` is
parallel to the feed arm of the dish.

When we can get out (!!), M1CRO/P use a PF dish on 13 (and 9) but on 6
and 3cm a 90cm (old, round) `Sky` offset dish is used; mounted
horizontally.
We don't need to mess about with dish tilt angles. You will need to
ensure your feed is correctly orientated for horizontal polarization.
but it won't matter how the dish `tilt` mechanism is set up.

We assemble with the arm vertically straight down at the rotator
setting (whatever the luffed tower direction is) using a level or
plumb-line and merely peak the dish on the beacon when upright. If you
are using a standard rotator (as we do) you will not get better than
+/- 3 degrees accuracy anyhow.
Simple matter then, if necessary, of altering the pointer on the
controller a little to align it up.
OK. We have a couple of local beacons; which helps.

I think that our results show that on those higher bands - with
narrower beamwidths - `it works`.
I expect you'll find the same on 13cm.

Dave, G1OGY

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