[TenTec] Station power supply??

[Jim Brown]

On 9/6/2012 1:12 PM, Don Allen wrote:
> A quick question:  Is it best to connect equipment together from 
> chassis to chassis, or from each individual chassis to a single point 
> ground?  I was taught it's best to connect each to a single point 
> ground point, e.g. to a copper buss bar behind a shelf. And, should it 
> be a short fat copper wire, or short wide copper strap? The latter is 
> certainly better for an RF ground.

The advantage of wide braid or wide copper strap is SLIGHTLY lower 
inductance, and slightly reduced resistance due to skin effect. At power 
frequencies, it's all Ohm's Law -- conductor cross sectional area and 
conductivity (that is, copper as opposed to steel or aluminum) are all 
that matter.  Braid is good INDOORS, but exposed braid oxidizes quickly 
outdoors.

Star or chassis to chassis?  For hum/buzz, what matters is DC resistance 
between boxes having unbalanced baseband connections between them 
(audio, RS232), so short fat copper between them is best. From an RF 
point of view, as long as those connections are all very short and the 
combination of them (or the chassis of the transmitter) are well bonded 
to ground, there's no significant difference between this and the 
so-called star.

The most important part of ANY grounding scheme is that ALL GROUNDS MUST 
BE BONDED TOGETHER, and by the shortest practical path.  That means 
power system, CATV, telephone entry, satellite dish, lightning 
arrestors, ham antennas, ham shack. The fundamental intent of all of 
this is that in the event of a strike, every part of the system rises by 
the same voltage.

One set of bonds is the Green Wires that run from the main breaker panel 
to all outlets, and are bonded both to Neutral and to earth at that 
panel.  That takes care of both protecting personnel and property from 
an electrical fault in a piece of connected equipment, and also limits 
the amount of voltage that is induced in power wiring in the event of a 
strike. It also limits the voltage between Neutral and Green.  An 
important function of the Green wire is to cause a fuse or breaker to 
blow in the event of an equipment fault.

The NEC DOES call for proper grounding of antennas, but it's not in the 
part of the NEC that most folks read.

73, Jim K9YC