On 3/21/14 6:41 AM, Charlie Gallo wrote:
On 3/21/2014 n8de@thepoint.net wrote:
...snip...
Think of the 'ground bar' as a series-string of very low value
RESISTORS.
Now ... think of your equipment as being connected to the 'nodes'
between each of those resistors ... rig A at one end, then rig B
at the first 'node' ... rig C at the second 'node' ... etc.
...snip...
Now thing of it a slightly different way.. The center of the bar has
the cable to ground, and each section of bar is a LARGER conductor
(aka lower impedance) than a wire the same length (greater cross
sectional area - hence my question RE SIZE and material), and the
wires are shorter. The lumped impedance is therefore lower, as far
as I can tell
Depends on whether you're talking about 50/60 Hz line or lightning or
HF. For line frequency, yes, the Z is lower with the big pipe/bar; for
1 MHz and up (lightning) the inductance dominates, and there is very
little change in inductance with conductor size, it's almost entirely
determined by the length, which is roughly 1 uH/meter. (going from a
1x1 cm square to a 0.2 x 20 cm sheet changes the inductance something
like 20-30%)
And in either round or wide flat, the impedance due to inductance is
typically orders of magnitude bigger than the AC resistance
However.. by far and away, the most common death, injury, or damage
scenario is a contact between power line and antenna or equipment.
(either internal short inside box from power wire, or something outside)
There's a lot more of those than there are lightning strikes or
transients. So, maybe we should be focusing more on 60 Hz bonding and
whether it can take the fault current from a MV distribution line that
contacts your antenna.
Assume the grounding points on your rig, and your amp are 36 inches
apart (as they are if you have an FT-1000MkV field and an Alpha 78
next to one another with the amp on the right). You can run say two
18" lengths of braid to a common point, for 36 inches (tight
stretched, but all it 40 with droop etc), OR you could put in a buss
bar that is 36" long, and 2x 4" jumpers to said buss. Total length
is about 4" longer, but the BUSS is more conductive than the braid
Which gives you less poof?
either would work. the key is that they are bonded together. The
differential voltage will be small.
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