How to build a K9AY from parts
This article is how a K9AY switch-able receive antenna was built by Darren Hatcher, G0WCW. Unlike some descriptions found via Google, it also goes a step further telling you really how to do it, rather than suggesting what to do.
The text and images in this article show a K9AY project prototype (the Project), as built from Gary Breed's (K9AY) original QST article.
If there are any copyrights on this, they are probably with Gary, so this is acknowledgment here - thank you Gary!
The images on the last page (8) in this article are deliberately large (700k) so if needed, you can study them for your design.
Synopsis - What is this all about? Just what is a K9AY? Why would I need one?
A lot of today's modern home-based radio stations, whether ham or shortwave listeners, need to be able to hear the weak signals in the ever growing noise. Often, this can only be done with directional antennas and this can be expensive to implement at low frequencies. A recent design by Gary Breed, K9AY, produced a terminated loop antenna that can be electrically steered from a remote location. It offered directivity to remove or find signals and required smaller space than earlier EWE designs. This meant it was far more portable, can be easily built and can be used in smaller gardens/backyards (which is also now more common).
A copy of the original K9AY article is here. Or you can get a re-print of it inside the ARRL's book on wire antennas, 'ARRL's More Wire Antenna Classics'.
Take time to read the original article to understand the on-air performance you can expect, what components are required to build one and the level of expertise required to build and test.
For the sake of brevity, throughout this article, the radio station end we'll call the Station Switch Unit (SSU or the big box) and the antenna end the Antenna Relay Unit (ARU or the little box).