[600MRG] E-Field Antennas - Transformer System Optimization

[Frank Lotito]

Recently there were a few postings regarding E-Field type vertical antennas, alla the VE7SL design.  Very interesting and thought provoking, and a bit confusing for what may not have been said. I'm still trying to get my brain in gear w.r.t. why the results of my experiments with ferrite transformers do not produce the ideal results many articles allude to.  I have 2 questions, the first regarding the E-Field antenna transformer system.


As I understand E-Field antennas, they are modeled as a high impedance series circuit - a very low resistance (the total sum of the radiator's radiation resistance, loss (skin and simple ohmic) resistances, and the antenna's capacitative reactive element, which is a very small value capacitor.


For the VE7SL type of antenna this low resistance small value capacitor series circuit becomes the load on the antenna transformer's primary, something in the order of 80 turns wound on a high-mu ferrite toroid core.  That transformer's secondary (some 10 turns) feeds a low impedance twisted pair of wires to the primary of the receiving end transformer.  The secondary of the receiving transformer is connected to the LF / MF receiving converter, which may or may not include a low noise / high dynamic range preamplifier.  The input to the receiving converter may nominally be 50 ohms, maybe not.  The converter / preamp's input may be the gate impedance of an emitter or source follower input stage.


My first question: Has anyone looked at the total model of this two-transformer approach to see how the characteristics of "real" ferrite transformers, and receiver loading effects system gain and frequency response?  (The two referenced articles below talk about the "real" ferrite transformer, and how it very much sets the performance of the circuit.)  This total model may explain some of the recent investigators' experiences, and point to a way to optimize the performance of the antenna transformer system.


ref  (1) Wideband Transformers: An Intuitive Approach to Models, Characterization and design," by Chris Trask, Applied Microwave and Wireless, Pages 30-41, November 2001; (2) The ARRL book "Experimental Methods in RF Design,"  Hayward et. al., revised first edition, 2003-2009, ISBN 0-87259-923-9, pages 3.33-3.34.  Additionally, on pages 3.31-3.33 of the ARRL book, the authors talk about resonating the transformer's reactance to get a more desirable (ideal) transformer characteristic.


My second question:  Does anyone know of a Windows XP or Windows 10 compatible program that can be used to "decode" the 60 KHz transmission from the receiver's demodulated audio stream?


Thank you - 73 Frank Lotito  K3DZ / WH2XHA