41 inch Rod Antenna Basics
The field source is a sis per 25 fixture (A 0.5 meter long wire suspended 5 centimeters over a ground plane) and driven at a nominal 0 DBM from 150 kilohertz to 30 megahertz.
It has been incorrectly claimed by people investigating the system for 25 technique that floating the counterpoise collapses the field measurement by 20 DB.
In fact the difference outside of the unwanted resonance when the counterpoise is grounded is just a few DB and that value is correct.
It reflects the nonzero potential on the floated counterpoise when it is raised above the floor in the presence of the fringing field from the radiating fixture.
This is the sis per 25 fixture driven from the tracking generator of a siglent spectrum analyzer. The analyzer has been placed under the counterpoise adjacent to the ground point so that the viewer can observe the effect of grounding and floating the counterpoise.
Instantaneously the connection between the 95010 rod antenna and the analyzer is via a montina fiber-optic link maintaining isolation of the counterpoise except when desired. We are observing the signal from the antenna with the counterpoise floating. The signals flat at minus 60 DBM again with the counterpoise floating a piece of coax has now been connected to the counterpoise and will momentarily bit connected to the floor. (the ground counterpoise).
When we ground the counterpoise using lengths of coax as might be used if a fiber-optic link weren't available we see about a 4 DB rise of the flat portion of the response and of course we see the characteristic resonance that is the aim of everyone to eliminate:
I sincerely hope this ends the claim that floating the counterpoise reduces the measured signal by 20 dB.