Just discovered a dinky 20m yagi. made from wooden dowel with an 8ft
square section to connect the two ends, the electrical parts are
simply wire where required.

Being 8ft across the ends and slightly more lengthwise to allow for a
turning radius, it looks like it could fit in my loft. I already have
a lightweight rotator that could handle that. I think it was supposed
to be a caravan tv aerial originally.

To make things even lighter I wondered if I could use pvc conduit with
alloy tape as the elements? Either way I think ist worth a go.

My problem is my rotator, it has twin core cable from its little
remote, so theres no way to determine where Im pointing.
So thats my query, anyone any ideas how I can show something
downstairs, while this is turning in the loft?

Best I could come up with is to use some sort of lighweight
motor/gears arrangement to work a pointer, by splitting the feed cable
in two and using one as a feed for that,perhaps that would work?

1) It stops at one point and must be reversed.
2) It cant turn continuously.
3 Dont know how real ones work at all.
4) No idea if a proper one can be jury rigged ro work here.

In article ,
Sniff ma Diff! wrote:

To make things even lighter I wondered if I could use pvc conduit with
alloy tape as the elements? Either way I think ist worth a go.

In my experience, PVC conduit tends to sag if used for horizontal
elements... it needs to be supported every few feet or it will
"droop".

My problem is my rotator, it has twin core cable from its little
remote, so theres no way to determine where Im pointing.
So thats my query, anyone any ideas how I can show something
downstairs, while this is turning in the loft?

That depends a lot on just what sort of rotator it is, whether the
remote is intended to have any sort of display, etc.

Some old-style TV rotators were intended to be "self-aligning" by
means of a clutch... turn the knob all the way clockwise, wait until
the antenna stops rotating, turn the knob all the way
counter-clockwise, wait until it stops, and you now know that the
antenna is certain to be all the way at one end of its travel (e.g.
due northwards, if that's the way you originally mounted it) and you
can rotate it back to any desired direction.

If worse comes to worst you may need to add some sort of extra readout
sensors - e.g. a multi-turn potentiometer, linked to the rotating part
of the mast through a belt or idler-pulley arrangement - and run an
extra set of sensing wires down to your shack.

Best I could come up with is to use some sort of lighweight
motor/gears arrangement to work a pointer, by splitting the feed cable
in two and using one as a feed for that,perhaps that would work?

Depends if the feed cable has a separate ground (braid) or is just the
two leads.

I think we need more details on just how your rotator works (and is
wired) and how the antenna is wired up, to offer good advice.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

On 9/1/2011 12:01 PM, Sniff ma Diff! wrote:
My problem is my rotator, it has twin core cable from its little
remote, so theres no way to determine where Im pointing.
So thats my query, anyone any ideas how I can show something
downstairs, while this is turning in the loft?

The beauty of usenet is it allows all sorts of characters to post.
Typically, in response a simple question it turns into some insane
"How esoteric and complicated can I make this?" contest.

So, with that thought in mind....

You have a rotor, you have two wires between your radio shack and
the rotor.

Since everyone seems to think that broadband over power lines is
such a "Good thing(tm)" here's a solution to your problem.

Use your two wire feeder to supply a fixed AC voltage to run the
controllers and the rotator.

Feed a digital control signal up the power line to tell the rotor
which way to turn.

Feed a digital signal back down the power line with the telemetry
to feed a display of which way the rotor is pointing.

Obviously since you have a bi-direction data stream on the power
line to the rotor, you can get as complicated as you want with the
amount of extraneous details. Such as slow start, brake clutch on
and off.

In fact, since you're already in the roof, add a weather station
outside and feed that data back down too. ;-)

Jeff-1.0
wa6fwi


--
"Everything from Crackers to Coffins"

"Dave Platt" wrote in message
...


snip

If the rotator doesn't
have a clutch - if you're actually "stalling" the motor when it hits
the end-stop - then you shouldn't keep running it past this point
(might overheat the motor) and should stop rotating when the motor
stalls and the current jumps upwards.


I like that wris****ch concept. But the quoted passage gave me another
idea. If the stalled rotor current is appreciably higher than the
operating current, then that's his end-of-travel indicator, right there. I
can check it myself and the OP will also need to.



Sal

On Thu, 01 Sep 2011 18:01:54 +0100, Sniff ma Diff!
wrote:

My problem is my rotator, it has twin core cable from its little
remote, so theres no way to determine where Im pointing.
So thats my query, anyone any ideas how I can show something
downstairs, while this is turning in the loft?

Sure, salvage some components out of some dead mice or printers and come up with
an optical positioning indicator using the salvaged IR emitters and receivers. A
simple cardboard disk with slot(s) that will let you know when it is in certain
positions. The more you use, the more accurate the positioning. You could make
it simple, or more complicated by encoding the signals. You didn't say you
couldn't run new wires, just asking if you could send a control signal down one
of the wires already there, so I hope this isn't a complete waste.

Bob, KB2ZGN