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
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|
