[TenTec] Radials

[Lee K7tjr]

I have to disagree that there is no advantage to having radials resonant or of a controlled length.. I have made extensive measurements of the surge impedance of radials ( by measuring single radials referenced to a large field of radials) of different lengths and over different ground conditions... Yes there is not much change in efficiency however there is a very significant change in the amount of unbalance of the load on the transmission line.. Not a problem if you are using a balun on your vertical. This unbalance will kill the patterns on a multi vertical array.. With a radial system of a free air 1/4 wavelength the actual lowest surge impedance of a radial is significantly lower in frequency due to the propagation velocity of the soil and it has a significant reactance. My opinion is that a radial system  of widely varying lengths will provide the most consistent measurements due to  the varying conditions of the soil caused by  weather such as rain and dry spells.. Also the fewer radials in a system the worse the unbalance. Although ground rods and large plates and screens don't seem to affect efficiency much it is my contention that they really affect the current flowing on the outside of the transmission line. And so does radial fields that have very few radials or might be highly inductive. The ultimate engineers nightmare to figure out mathmatically what the parallel equivalent impedance is of 60 radials with a different resonant frequency and loss characteristic due to varying ground conditions. Suffice to say put up as many radials as you can of varying lengths really works. None of this probably is of much use to the average antenna user however if you are trying to get a 30 db front to back ratio you cannot without knowing where all the current is going even the tiny little bits that are 30 db down. I believe there is still a lot more to understand about our antennas and radial systems.

Lee K7TJR