[TowerTalk] station grounding question

K8RI on Tower talk k8ri-tower at charter.net
Tue Nov 29 00:55:13 EST 2005

> If you want the best isolation of equipment, a separate ground lead from
> each piece of equipment or rack of equipment would be run to the single
> point ground plate. That would eliminate currents being fed from one piece
> of equipment to another.

Only if each lead is the same length and the same impedance/reactance.
The rapid rise time for the current and the wide range of frequencies means 
only a slight difference in "electrical" length could cause large voltage 

>Ideally ALL connections to each piece of equipment
> should be directly referenced to the single point ground and not directly 
> to
> another piece of equipment. The Motorola grounding specs call for this 
> type
> of grounding of equipment. However this can't always be done due to
> interconnections of signal paths between equipment.
> You don't particularly care if all equipment is maintained at the exact 
> same
> potential during a lightning strike. What you do care about is that all
> connections to a particular piece of equipment have equal potential. This 
> is
> within reason of course as great differences between equipment can result 
> in
> flashover between them.

If the equipment is interconnected I would think keeping the voltage to a 
minimun would be a must.
My computers are all hard wired together through a Cat5e network with the 
cable to the shop running within 10' of the tower base.  It also runs part 
way right with some of the coax runs.  The serial ports of three computers 
connect to the radios. The audio lines connect to two of the radios.

Some of these are not only on seperate circuits, but on seperate Feeds from 
the power company and over 100' apart.

> As far as shock hazard is concerned you do want all equipment at the same
> potential as earth.
> Grounding equipment to keep it at earth as far as RF is concerned normally
> should not be a concern. If there are RF problems on equipment chassis 
> there
> are usually other problems that should be addressed.
> As far as induced currents into equipment in the shack, it is important to
> keep lengths short between the single point ground and the equipment. It 
> is
> also very important to not have the protected side of the single point
> ground panel wires close to or parallel with the unprotected side wires.
> All unprotected lines should be kept well away from protected lines that 
> go
> to equipment.

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
> 73
> Gary  K4FMX
> _______________________________________________
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