Topband: Coax Shield vs. Ground & elevated radials

[Tom Rauch]

Update: I added the choke at the antenna base. Before doing 
that I created a
probe by wounding abt 15 turns of enamelled wire around the 
coax close and
localised a point on the coax with a maximum reading close 
to the shack>>

The magnetic field from common mode currents is in the form 
of rings around the coax. Consider the coax an axle or axis, 
the magnetic field would be a ring.

As a consequence your winding would have to be a small 
spiral circling the circumference of the coax. You could not 
wind it directly around the coax like the coax is a core or 
you would not read what you think you are reading.

This is why the only reliable method that works is a 
soft-iron core that circles the entire coax and you wind a 
small winding on that core.

See:

http://www.w8ji.com/building_a_current_meter.htm

73 Tom