Tom, I can answer a few of those questions.
-----------------------
The obvious thing is a wiring error you don't know about,
but let's assume it is all OK. I'm also assuming several
others have very similar setups without any issues.
Yes, it doesn't sound like a wiring problem.
-------------------------
I'm not at all familiar with the SteppIR design, but I've
done tons of control systems over long distances myself. One
thing that can happen is a ground loop between the tower
ground and the house ground if anything in the control line
system is grounded at both the house and the tower. Normally
the coaxial lines provide a low enough impedance path to
prevent significant potential from the different earthing
points, but problems can happen. I'm assuming the coax is
grounded well for dc at the tower and the shack ground.
The control cable is 16 twisted pairs with an overall shield. The
shield should be connected to ground at both ends. There is no
connection between motor wires and ground at the antenna end, so ground
loops should not present a problem.
-------------------------------------------
Also some control systems don't like a capacitive load.
This one included.
------------------------------------
I don't have a high level of confidence when dealing with digital
engineers and long cables.
Me either.
---------------------------------------
Are there sensitive leads that need to be in a different cable away from
motor leads?
No, there are only motor leads.
-----------------------------------
Is there something like a crowbar that shuts the system off on overvoltage?
That would be in the power supply, and since I don't have a schematic I
don't know for sure, but I would bet no.
----------------------------------
Is there a diode or gate protection in a chip that dumps a transient
from control or motor leads back into the supply and somehow crowbars it?
Max motor peak currents (differentially) are limited by motor DC
resistance and inductance. There is no limiting for currents to ground
or other lines. I would bet there is no crowbar, but I don't know that
for sure.
---------------------------------------
I'd look at the control lines with a triggered or better yet a storage
scope for transients. See what you got for spikes.
73 Tom
That would be a definitive test.
Jerry
Tom Rauch wrote:
>>What about the possibility of a ground loop that doesn't
>>manifest itself
>>until there's 4 elements connected??
>>
>>
>
>The obvious thing is a wiring error you don't know about,
>but let's assume it is all OK. I'm also assuming several
>others have very similar setups without any issues.
>
>I'm not at all familiar with the SteppIR design, but I've
>done tons of control systems over long distances myself. One
>thing that can happen is a ground loop between the tower
>ground and the house ground if anything in the control line
>system is grounded at both the house and the tower. Normally
>the coaxial lines provide a low enough impedance path to
>prevent significant potential from the different earthing
>points, but problems can happen. I'm assuming the coax is
>grounded well for dc at the tower and the shack ground.
>
>Also some control systems don't like a capacitive load. I
>don't have a high level of confidence when dealing with
>digital engineers and long cables. Are there sensitive leads
>that need to be in a different cable away from motor leads?
>Is there something like a crowbar that shuts the system off
>on overvoltage? Is there a diode or gate protection in a
>chip that dumps a transient from control or motor leads back
>into the supply and somehow crowbars it?
>
>I'd look at the control lines with a triggered or better yet
>a storage scope for transients. See what you got for spikes.
>
>73 Tom
>
>
>
>
>
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>
>
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>
>
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