[Lowfer] Embattled E-Probe

[Bill Ashlock]

Peter,

>>BTW on the subject of E-probes and needing to be "in the clear": I
>>would certainly agree with this theme if we are talking about clearance 
>>from
>>other antennas or metalic objects equal or higher above ground than the
>>probe. In the woods or in trees I find this rule does not apply.
>>Bill A

>Okay, let me see if I understand: These natural 10K objects are,
>because of this property, able to induce a voltage into a nearby probe,
>whereas surrounding metal structures with near zero-K properties cannot
>and further act as a signal shield instead.

Yes, a simplified LF model of a tree is a BIG metallic horizontal sheet of 
metal at the top of the tree and a long resistor connecting to the ground 
with a total of ~10k. The signal strength found by a hi-Z probe, close to, 
or touching the trunk, is proportional to the point where the probe is 
located relative to the signal at the top total. For example, half-way up 
would be half of the signal.

This model totally fails at LF if the trunk has a low resistance because it 
short-circuits the signal picked up by the top of the tree. Low resistance 
trees would also shield the signal from the tree under test. (IE: the King 
TUT <sorry>)

My tree antenna is strictly a top feeder that has an 18ft bare wire in 
contact with the top branches and I match to the coax down lead with a 10k 
ohm to 70 ohm transformer (other lead from the transformer goes to a ground 
rod at the base). I've also tapped directly into the trunk of my tree about 
1/3 of the total height with a spike and used a reduced transformer ratio to 
the coax. This works, but it's not quite as efficient as the top feed.

Bill A

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