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Old 21st Oct 2020, 10:30 am   #1
Steve G4WCS
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Default Antenna rotator

Not quite vintage but Ive a yaesu g-400 rotator with the round dial controller with an issues so Im calling on the collective

Ive noticed the antenna has gone about 90 degrees out to the controller needle position, the needle does stop a bit at a couple of points and presumably over many rotations backward and forward this hysteresis is adding up. Am I right in thinking that (for now until I can investigate) if I set the antenna position to North (reference point for the controller) then disconnect the rotator from the controller and set the controller to north, then it will all be back in sync.

Googling is pointing to the rotator pot needing changing. Ive attached images of the ones supplied by an antenna place, can I assume that the RS components pot will be a suitable alternative ?
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Old 21st Oct 2020, 11:15 am   #2
Malcolm G6ANZ
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Default Re: Antenna rotator

The pot from GB antennas looks like a single turn 500 ohm standard pot. The ones you have shown from RS are multi-turn ones and not suitable.There are several advertised on E Bay but they all live in Hong Kong
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Old 21st Oct 2020, 11:22 am   #3
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Default Re: Antenna rotator

Has the antenna moved 90 degrees round the stub mast, or perhaps the rotator has moved 90 degrees round the main mast? Could be a combination of both.
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Old 21st Oct 2020, 12:32 pm   #4
Steve G4WCS
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Default Re: Antenna rotator

Well spotted on the pot. I don't think anything has rotated relative to anything else, I'll have to crank it down and have a check.
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Old 21st Oct 2020, 1:41 pm   #5
PeterRoberts
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Default Re: Antenna rotator

Hi Steve,

I've not got one of these, but an earlier Kenpro KR400RC, which is basically the same.

Have you looked inside the controller? It doesn't really sound like a pot fault, unless one or other (in controller & rotor) has become physically loose and has turned. If either pot was electrically faulty I would expect random and/or uncontrolled movements of the pointer.

Inside the controller I believe that there are a couple of gears driven by a motor to rotate the pointer and that one of these is nylon/plastic and can sometimes split and so slip on its spindle. Worth checking out.

Also, can you not adjust the needle to point to the real position? Just grab hold of the white plastic knurled knob on the front of the controller in the centre of the dial and turn the pointer to the correct position.

Good luck,

Peter
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Old 21st Oct 2020, 2:14 pm   #6
dodgy-dxer
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Default Re: Antenna rotator

It could be some of the gears in the motor housing have stripped or the gear driving the pot in the motor housing which is plastic has worn/broken

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Old 22nd Oct 2020, 8:23 am   #7
Steve G4WCS
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Default Re: Antenna rotator

thanks for the replies, Ill investigate. Ive ordered a bulgin 6 way connector pair so it can be connected/disconnected more easily instead of the silly tagstrip
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Old 22nd Oct 2020, 11:33 am   #8
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Default Re: Antenna rotator

If it's the rotor I think it is, inside the controller, the motor drives the pointer via a gear train and it also drives a duplicate of the pot in the gear train inside the bell of the rotor proper up the tower.

This pot does just as much rotating as the main one, but it's in a nicer environment.

There is a possibility of wear in the gearing causing teeth to jump and a relative error builds up.

The motors can just rotate indefinitely. The alignments which are important are the bell position (meaning its stops) with respect to the pot position, and the pointer position (meaning its stops) with respect to its pot position.

The pointer can be loosened and moved, also the stub mast can be loosened and rotated. People do this so that they can place the stops position, that can't be rotated through, at a convenient compass heading they rarely use.

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Old 24th Oct 2020, 7:33 pm   #9
Steve G4WCS
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Default Re: Antenna rotator

DOH. Ive only done a 360 rotation with the mast down with the 5 element. Of course the 7 element LFA is longer, and therefore catching on the house. I feel very silly now. Will have to crank the mast up and see if turning the pointer will realign everything (and put a big post it note on the controller to check the mast is up before rotating)
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Old 24th Oct 2020, 9:17 pm   #10
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Default Re: Antenna rotator

If your rotator had been big enough, it would have turned the house...

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Old 25th Oct 2020, 8:51 pm   #11
Steve G4WCS
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Default Re: Antenna rotator

I've had a play for an hour tonight. It's going to need the beam setting to North then the controller disconnecting and setting to North. There,s a stop in the controller which I've just moved from North to West by turning the pointer on the controller. Was having a listen out for beacons via aurora but nothing doing
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Old 6th Nov 2020, 8:29 pm   #12
Steve G4WCS
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Default Re: Antenna rotator

Its sorted. Had to rotate the antenna round on the stub mast. Also took advantage of the weather, upgrading to low loss feeder, and a gaasfet lna at the masthead
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