[TowerTalk] SteppIR problem

[Tom Rauch]

> 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