[TowerTalk] Station Ground

[Jim Lux]

At 02:49 PM 1/14/2005, you wrote:
>Kelly, and TT:
>
>One reason for the desirability of broad, flat ground conductors at 
>RF,  is that the series inductance of such is much less than "round" 
>conductors of any manageable size... While a narrow stricture somewhere in 
>the conductor should be avoided if possible, and it is difficult to avoid 
>entirely, you still gain benefits from the broad conductor contributing 
>less total inductance to the ground system....even if in series with a 
>small run of narrow conductor...

True enough, but I am unconvinced of the need for a low inductance 
connection from a modern radio to ground.  Of course, if you're using an 
older rig that's AC powered (I'm thinking about my dad's DX100, for 
instance, that had a fused 2 prong plug), you NEED a separate ground wire, 
but it's a "greenwire" safety ground, not an RF ground. However, modern 
radios have safety grounding through the power cord.  Belt and suspenders 
is ok, however, having two separate grounds, especially if one goes to that 
ground rod outside the window, and the other goes through the wiring of 
your house back to the service entrance panel, is asking for ground loop 
and transient trouble.


Sure, if you have some sort of single ended antenna tuner, and a single 
wire going out to your Marconi fed antenna, yes, then the ground connection 
of the tuner is part of the RF path, so inductance is important.  Or, even 
if you have a balanced line, you probably want to ground the tuner, because 
even balanced lines are connected to antennas that are not perfectly 
balanced, so the tuner chassis becomes part of the RF circuit.

But, if the chassis ground is for electrical safety.. you're worried about 
60 Hz, not RF.

Hopefully, your system is put together in a way that no RF power is flowing 
through the chassis (in fact, I would argue that putting chokes on the 
ground wires might be a good idea).

If you're getting RF burns or tingles from the mike, putting a ground wire 
in might help the symptom, but it's not solving the real problem.




>73, DX, de Pat AA6EG   aa6eg at hotmail.com


Jim, W6RMK