[TenTec] RFI Issues

[Jim Brown]

On 5/17/2012 1:13 PM, Stuart Rohre wrote:
> Jim I respectfully disagree, as I have seen examples of radiating
> "ground" wires causing RFI.

Since you didn't quote any part of an email, I have no idea what you're 
disagreeing with (or even whether it's me or another Jim that you're 
disagreeing with).

That said -- a wire going to ground is no different from any other 
wire.  If it carries RF current, it will radiate, and it can carry a lot 
of RF current if we allow it to become part of a transmitting antenna 
system.  The most common way that happens is by using a long wire or 
vertical antenna and forgetting to provide a counterpoise for antenna 
current.  When we do that, anything connected to the transmitter chassis 
becomes the counterpoise by default.

SO -- if a "ground" conductor is radiating, it's an ANTENNA problem, not 
a "grounding" problem.  The ground wire(s) MUST be there for reasons of 
lightning protection and electrical safety.

Example -- back when I lived in Chicago, my shack was on the second 
floor, my antennas were bonded to a station ground, which was bonded to 
power, telco,  some rods, and a big wrought iron fence that ran around 
the front of my lot.  My 160M antenna was a vertical random wire formed 
by tying both sides of the feedline together and loading it against that 
combination of grounds (including the fence).  The big #4 copper that 
ran from the second floor shack to those grounds and that fence WAS part 
of the antenna, even though it was CALLED a "ground" wire, and it 
contributed to the total radiation.

Another point.  A radiating wire does not CAUSE RFI.  Badly designed 
equipment causes RFI, either by letting RF into the box, or by emitting 
RF trash from the box.

73, Jim Brown K9YC