[TowerTalk] SHACK LOCATION VS GROUNDING & RFI

[Jim Brown]

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