Re: [TowerTalk] Station Ground

[Jim Lux <jimlux@earthlink.net>]

At 01:39 PM 1/14/2005, you wrote:
> How do people attach their rigs to a bus-bar (or
> similar)?  The bigger the ground wire the better,

WHy would you necessarily want a huge wire?  How much current do you expect 
to be carrying through that wire?  Hopefully not much. Sure, bigger is 
(slightly) lower inductance, but presumably, the wire is fairly 
short.  Also, is the rig chassis ground common with the power supply return 
(if 12V powered)?  What about the electrical safety ground (the greenwire 
ground)?

Think about why you're grounding the rig chassis in the first place.  Draw 
a grounding diagram of all your equipment and make sure you've got a 
reasonable grounding tree.  A lot of the "traditions" in grounding come 
from days before 3 prong plugs, for instance.

It's awful easy to get ground loops where you don't intend them, or to get 
the chassis RF hot.  Much better to have the RF return current flowing on 
the inside of the coax where it belongs, rather than through the chassis of 
the device.

If chassis and the 12VDC return are connected internally, you also don't 
want the chassis ground being lower impedance to the power supply than the 
intended 12VDC return wire, or your ground connection will carry more 
current than the power supply wire, which is NOT a good thing.

If the purpose of chassis grounding is for electrical safety, then the 
ground connection needs to carry enough current to make sure the breaker trips.

If the purpose of chassis grounding is to provide a path for a transient 
suppressor on the input, then short & low impedance is the goal.


>  but
> most rigs/amps have small, somewhat fragile grounding
> posts.  How do others out there connect a nice
> hefty ground wire to their rig or amp?  Also, how
> do people attach the wires to the bus-bar or
> ground rod?  Bolts?  U-Clamps?  Solder?  Any
> advice would be appreciated.

Jim, W6RMK 


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