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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
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21st Oct 2020, 11:30 am | #1 |
Heptode
Join Date: Sep 2004
Location: Preston, Lancashire, UK.
Posts: 632
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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 ? |
21st Oct 2020, 12:15 pm | #2 |
Octode
Join Date: Feb 2006
Location: Bristol, UK.
Posts: 1,030
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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
Malcolm |
21st Oct 2020, 12:22 pm | #3 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
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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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21st Oct 2020, 1:32 pm | #4 |
Heptode
Join Date: Sep 2004
Location: Preston, Lancashire, UK.
Posts: 632
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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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21st Oct 2020, 2:41 pm | #5 |
Pentode
Join Date: Dec 2011
Location: Camberley, Surrey, UK.
Posts: 145
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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 G4DJB |
21st Oct 2020, 3:14 pm | #6 |
Heptode
Join Date: Mar 2008
Location: Newmarket, Suffolk, UK.
Posts: 611
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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
Fred G4BWP |
22nd Oct 2020, 9:23 am | #7 |
Heptode
Join Date: Sep 2004
Location: Preston, Lancashire, UK.
Posts: 632
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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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22nd Oct 2020, 12:33 pm | #8 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,801
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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. David
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24th Oct 2020, 8:33 pm | #9 |
Heptode
Join Date: Sep 2004
Location: Preston, Lancashire, UK.
Posts: 632
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Re: Antenna rotator
D’OH. 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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24th Oct 2020, 10:17 pm | #10 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
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Re: Antenna rotator
If your rotator had been big enough, it would have turned the house...
David
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Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
25th Oct 2020, 9:51 pm | #11 |
Heptode
Join Date: Sep 2004
Location: Preston, Lancashire, UK.
Posts: 632
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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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6th Nov 2020, 9:29 pm | #12 |
Heptode
Join Date: Sep 2004
Location: Preston, Lancashire, UK.
Posts: 632
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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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