On 7/8/2013 3:17 PM, Jim Lux wrote:
On 7/8/13 9:37 AM, K8RI wrote:
On 7/8/2013 10:33 AM, Jim Lux wrote:
On 7/8/13 7:18 AM, john@kk9a.com wrote:
I also have a shack on the 2nd floor and I also disconnect all cables
going to the tower. I only use the station for major contests so doing
this is not really inconvenient. Disconnecting however is not a
reliable
means of protection as the energy can be induced into anything
nearby. I
am not sure if there is any way to stop this from occurring. Even if
you
disconnect it is a good practice to have multiple lines of ground
rods a
single point ground and MOVs or GDTs on every rotator and relay.
John KK9A
I'm not sure about the value of the multiple lines of ground rods *from
the entrance panel*. I just don't see the physics of what it's doing
there. The goal at an entrance panel is to have everything tied to one
reference voltage, and let that go up and down.
That is for operating on multiple bands to prevent the rig from rising
too far above ground Recommended by ARRL.
Exactly where is this recommended by the ARRL (so I can go find it...)
IIRC It's in the hand book, I'll see if it's in the current edition i
have on the computer
Is that the "tuned ground wire" thing? where you put half a wavelength
at each band of interest, on the assumption that a transmission line
repeats the far end impedance at every half wave.
I don't think that has any validity for lightning (and it's dubious for
Tx or Rx, as well).
What you're concerned about, presumably, is that the coax ground isn't
too different from the equipment chassis ground. That's easy: a
reasonably short wire between equipment and coax entry point.
The multi length ground is an operational ground and not a safety ground
for lightening.
For a lightening pulse that could mean thousands of volts.
Although we think of lightening as static, it is not DC. The sharp rise
and fall times mean it's much more like medium frequency with most of
the energy lying near, or in 160 meters. OTOH Lightening strokes are
pretty much unique with no two being identical.
I don't know that the voltage of the chassis, relative to some distant
point outside, has a lot of importance. After all, planes have no
ground wire or rod, get hit by lightning, and keep on working.
Not necessarily. Even large aircraft have received substantial damage
from strikes while airborne and some have been brought down.
I've never had a plane struck, but coming back from Denver in the
Debonair, I had such a static build up, all the radios quit working and
I had to power down the whole panel and reset to get them back up.
ATC was kinda excited when I came back on as they had lost the
transponder return. They understood when I explained. I had to do a
reset twice in that area. Man, what a ride! Flying blind in that stuff
(all the electronic instruments quit!) is exciting. It's like partial
panel while on a roller coaster and no visibility.
73
Roger (K8RI)
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|