[600MRG] Active Antenna Recommendation

[Frank Lotito]

For the past few days there has been some activity regarding a question posted on active antennas.  From a theory point, what I know about antennas would easily balance on the "tip of a sharp needle."  I have a few questions that you may be able to help me with:


(1) For E-Field probe antennas (and H-Field loop antennas) how does one determine that there is a need for common mode decoupling?  For any particular setup-up I assume the need for decoupling is very frequency dependent.


(2) Reference the AMRAD article in QST by K0BRA for an active LF E-Probe antenna design: The AMRAD author(s) suggest that a wire screen be placed just below the probe's feed point to "stabilize the E-filed." (See the Siting and Installation section of this article.)  In the recent 600mrg post on this topic, a reader replied that the mast forms part of the total antenna and the drain follower (cathode follower, or what ever) is tapped off-center and towards one end of the total antenna (probe plus mast.)  I am confused - what am I missing?


(3) Any guidance on how one would determine if an E-Field antenna (and for that matter, a tuned H-Field loop) is dangerously coupled to the transmit antenna and some form of "protection" is required to keep from blasting the active antenna to kingdom come?  My stuff is home brewed. Blow it up - tough. For those with commercial active antennas, which I believe are reasonably water-proofed, you will be out a few bucks.


73 Frank K3DZ / WH2XHA