Grant,
Thank you for the info, there's a lot to
go through and hopefully something there
will help. I'm on a prosthetic leg now so
climbing the ladder to the roof to
experiment is something I want to do as
sparingly as possible.
Thanks for the good information.
73,
Gary
KA1J
> 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@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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