View Single Post
  #39   Report Post  
Old May 17th 06, 11:30 PM posted to rec.radio.amateur.antenna
Richard Harrison
 
Posts: n/a
Default FIGHT? Here is another W8JI myth bone!

Tom, W8JI wrote:
"I did not claim that effect. Terman certainly did not. (Yuri claims the
shield "blocks electric fields" or stops "electrostatic fields".)"

I`ll requote Terman from page 38 of his 1955 edition which Tom ignored:
"It is possible to shield electrostatic flux without simultaneously
affecting the magnetic field by surrounding the space to be shielded wih
a conducting cage that is made in such a way as to provide no
low-resistance path for the flow of eddy currents while at the same time
offering a metallic terminal upon which electrostatic flux lines can
terminate."

That is a description of the shield on Terman`s direction finding loop.
The loop has a gap in the shield opposite its feedpoint. The gap
prevents current from circulating around the loop shield and thus
prevents creation of an opposing magnetic field by the shield to the
incident field acting on the loop.

The grounded shield nevertheless terminates electric flux shorting it to
ground.

The loop shield is thus a true Faraday screen, not a Faraday car body or
screened room.

Best regards, Richard Harrison, KB5WZI