On Sun, 6 Feb 2005 07:57:01 -0700, TOMMY HALIBURTON wrote:
>Has anyone successfully done a second floor installation?
Sure -- my shack is on the second floor, I run a big amp, and
grounding is not an issue. There are several keys to this.
1) A connection to earth has NOTHING to do with keeping RF out of
your gear, or out of your shack.
2) Most "RF in the shack" problems are really "pin 1 problems,"
both in ham gear and in equipment that you connect to ham gear.
Nearly all ham gear has pin 1 problems, and so do nearly all
computer sound cards. So you have to either fix or work around
these pin 1 problems. See the links below for an explanation of
the pin 1 problem. They're written for sound contractors about
audio systems, but the same principles apply to RF.
http://audiosystemsgroup.com/Pin_1_Revisited.pdf
http://audiosystemsgroup.com/Pin_1_Revisited_Part_2.pdf
3) The best way to keep RF out of your shack is to load it into
resonant antenna(s) at the end of a transmission line. That means
well-matched antennas, not all-band messes that depend on an
antenna tuner to keep the transmitter from shutting down.
4) I have an antenna that I load as a long wire on 160 and 80, and
this puts a LOT of RF in my shack, especially when I fire up the
amp. But because I've taken care of #2, I have no "RF in the
shack" problems. In contests, I key my radio from my laptop, which
is within a few feet of the antenna!
5) The purpose of a connection to earth is lightning protection.
It will NOT help RFI, nor is it even important for transmitting a
good signal.
6) What we often CALL a "ground system" for an antenna is really a
counterpoise that acts as the other half of the antenna to provide
path for current. For example, a long wire needs such a path. An
earth connection is NOT generally useful in this regard. Rather, a
network of radials is FAR more effective. I don't have room for a
lot of radials on my small city lot, so I've improvised by adding
a wrought iron fence that runs around the front of my lot to a
small radial system to act as a counterpoise.
Jim Brown K9YC
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|