[RFI] RFI cured with 1/4 wave wire

[Cortland Richmond]

On 2/20/2016 10:29 PM, Jim Brown wrote (in replying; single bar) :
>> Can I attach my radial system (which I would disconnect from the copper
>> pipe driven into the ground) to my L-network coupler and ISOLATE THAT
>> COUPLER FROM GROUND WITH A BALUN?
>
> That is a bad idea.
>
>> That would separate the RF ground from the Shack (lightning ground).
>
> That's also a bad idea.  Remember that lightning is NOT a DC event, is 
> an RF event, with peak energy broadly centered between about 100 kHz 
> and 10 MHz.  A radial system provides capacitive coupling to the 
> earth, so if it's part of the building ground, it lowers the impedance 
> to earth, so it improves lightning protection.
>
> Second, there is no such thing as RF ground.  For decades, we have 
> heard the same nonsense from the high-futility audio world about 
> separating the "clean audio ground" from the rest of "ground," which 
> is "dirty." Separated grounds are a really bad idea, especially at 
> RF.  Now, we DO use "isolated ground" wiring in power systems in 
> buildings to minimize circulating noise currents on sophisticated 
> technical systems, but every part of those systems IS grounded and 
> bonded in a very well controlled way, and all grounds are ultimately 
> bonded together. 
It's an interesting discussion.There is often a good reason to isolate 
an unbalanced antenna from the shack. IIRC, AM broadcast stations often 
use an air core transformer, with spacing adequate to allow lightning 
protection to fire and not arc to the transmission line.

I suspect that a tank circuit at the antenna tuner output, connected to 
the radials, could provide the LF steering needed to drain static there, 
and send tuner return current RF to the radials.  I used a shunt 
inductor in my mobile station, allowing easier matching to the low 
impedance of a 5 foot mast, loading coil, and whip, and on higher 
frequency bands [with the tuner in the trunk, eliminating precipitation 
static that would sooner or later have blown out the tuner -- or the gas 
protector in a transceiver.

It probably doesn't need saying that a connection to the house ground 
need not run to the station. It can go directly to the ground at the 
power entrance.

Cortland, ka5s