[TowerTalk] Alpa SPID RAK motor noise

Thu Oct 11 17:07:57 EDT 2018

Hi David,

Thanks for the info. The interference 
lasts well beyond the ramp up & down. GH 
had me try the max & minimum speed at 10 
to see if it was ramp up & down. It made 
no difference, the interference continues 
throughout rotation.

Gary
KA1J

> To test you can turn off the ramp up/down function in the gh
> controller.  It does make noise, but the noise is only there during
> the ramp periods, it is pure dc when it gets to full speed.  I think I
> have two .01uf caps at the controller between pins 1&2 which gets rid
> of most of it.  
> 
> 
> 
> David Robbins K1TTT
> e-mail: mailto:k1ttt at arrl.net
> web: http://wiki.k1ttt.net
> AR-Cluster node: 145.69MHz or telnet://k1ttt.net:7373
> 
> 
> 
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of
> Grant Saviers Sent: Thursday, October 11, 2018 19:58 To:
> Gary at ka1j.com; Towertalk at contesting.com Subject: Re: [TowerTalk] Alpa
> SPID RAK motor noise
> 
> Gary,
> 
> Checking the GH specs, "In most cases, adds PWM speed control" and
> since the Spid uses a DC motor, the GH is likely using PWM for ramp
> up/down.
> 
> So my thoughts of what should be done - to start, it isn't clear if
> this is brush noise or PWM noise
> 
> 0. run the rotator on pure DC from a linear power supply - no noise =
> pwm problems; noise = maybe both, your waterfall might help decide how
> much of either
> 
> 1. either problem, insure you have a good 6m feedline choke right at
> the feedpoint plus a choke at the entrance panel plus a choke at the
> base of the tower -
> 
> 2. either problem, use shielded twisted pairs for the rotator motor
> and position leads -   ground shields only at tower base
> 
> 3. if PWM noise
> 
>      choke the motor cable at the GH output for 6m to further knock
>      down any common mode PWM hash,  two, maybe three turns in a big
>      clamp on.
> 
>      ground the GH, maybe try 0.01uf to ground on both GH motor leads
>      and see if it tolerates them.  Try larger if it does.
> 
>      if this isn't enough it gets complicated, use a controller
>      without PWM,  add a common mode choke on the motor leads although
>      finding a commercial one for 50MHz and several amps is
>      challenging, make a low pass filter, muck around inside the GH
>      with its PWM switching risetimes, etc.
> 
> 4. If motor noise - I've seen bifilar windings on rod ferrites plus
> ceramic caps right at the brushes (better inside the motor) do a go
> job of suppressing hash. At 50Mhz you need SMD length cap leads - i.e.
> none. Rods and caps work on the K0XG 180vdc 1/2hp motors on my rings. 
> Also this is what K7NV does on his prop pitch motors and I hear only a
> very slight whine on mine, 80m and no PWM noise from the GH internal
> amp.   I don't have design details, perhaps others can provide advice,
> but the Spid motors are small in comparison.
> 
> I've been battling PWM amplifier noise for a couple of years with
> limited success, seven GH + remote commercial PWM amps for K0XG rings.
> Got it mostly tamed 20m and up, still struggling on 40m. I have a
> bucket full of filters I made that didn't work.  And I've added 
> bucket of big clamp-ons on everything.   Wish I had used shielded wire
> from amps to ring motors.  The reasons this is so hard are commercial
> PWM amps have all sorts of self protection stuff which don't like what
> would surely work as a low pass filter.  They also want the biggest HP
> rating in the smallest size so design for wicked fast rise times on
> the output IGBT. And the design does not at all have a balanced output
> or any filtering.
> 
> Grant KZ1W
> 
> 
> On 10/11/2018 8:25 AM, Gary Smith wrote:
> > There are four wires to the rotator; two
> > for DC and two for control. There are
> > small disc caps attached to each of the
> > control lines with a common wire to ground
> > which is screwed to the protective cover.
> > There are no caps I can see related to the
> > power side. There's a resistor in series
> > with the + line but that's not going to
> > help in this regard.
> >
> > http://doctorgary.net/spid-caps.jpg
> >
> > The black wire hanging down terminates in
> > a brass eye terminal that is screwed down
> > to the cover, this anchors to the metal
> > case providing the ground.
> >
> > Gary
> > KA1J
> >
> >> 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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