[TowerTalk] Alpa SPID RAK motor noise

[Jeff Blaine]

It's not the rotor - it's a side effect of the PWM coming from the GH 
controller and transmitted by the rotor wires.

73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com

On 11-Oct-18 6:55 AM, john at kk9a.com wrote:
> Inside all of my TIC Ring rotators are filters connected to the wiper
> motors. Perhaps a filter can be added at the Alpha SPID RAK motor to
> reduce the hash.
>
> John KK9A
>
>
> From:	"Gary Smith" <Gary at ka1j.com>
> Date:	Thu, 11 Oct 2018 01:39:41 -0400
>
>
> I have motor noise when I rotate the new
> SPID RAK & I've held off asking here till
> I completed properly grounding the house,
> coax & rotor lines. Unfortunately it
> hasn't helped the issue I'm having with
> the rotor and maybe someone has a
> suggestion of something I can try.
>
> The antenna is a 6M7JHV, it is on a tripod
> mounted in the center of the house. There
> is a #4 Gauge wire attached to the tripod
> which goes to an 8' ground rod. This
> ground rod is connected with #4 solid
> copper to the breaker box and the ground
> rod with the Polyphasers which goes to the
> shack, the ground to the shack attaches to
> this last ground rod. There are 3
> additional ground rods attached to the #4
> wire.
>
> When I turn the antenna it obliterates the
> waterfall and raises the meter 7 S units.
> As soon as the motor stops all is well.
> The controller is a GH RT-21D. The
> tailtwister it replaced never left any
> indication it was turning other than the
> meter.
>
> It was suggested it is because it is a DC
> motor in the SPID and the noise is likely
> coming from the brushes. Also that the #4
> to ground is not a RF ground and if it
> were attached to a tower instead of a
> tripod I likely wouldn't have this issue.
> The possibility was raised of the brushes
> having an issue or perhaps the two caps
> attached to the control lines to ground
> may be a problem.
>
> Here is a photo of the SVGA output from
> the K3.
> http://doctorgary.net/spid.jpg
>
> I started at 180 deg and rotated clockwise
> to 179 deg. The dark red is at 240-290
> degrees, the two strips of blue where
> there is no interference happens around
> 340 and 80 degrees respectively.
>
> I've never read of anyone having this
> problem before, guess I'm the lucky guy.
>
> Any suggestions I might try?
>
> Thanks & 73,
>
> Gary
> KA1J
>
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