Toroid coils are interesting in that they confine the magnetic field within the center axis of the toroid. Because of this, stray coupling seldomely causes a problem, but then again, coupling in general is not easy. So, I had the idea these would be my ticket to exploring designs with capacitive or link couplings between circuits. Eventually I began scouring the net and my books/references for circuits employing link coupling. This coupling method seems to come in two main varieties, tuned (such as found in the Crystal Set Societys' "My Marconi" set), and untuned (as found say in MRL's #42 set). Tuning the link is not needed, but it was something I wanted in an effort to sharpen the tuning overall. This method forms a triple-tuned set with its consequent quirkiness and occasionaly annoying tuning. Still, I find this part of the fun, I am not looking for tuning efficiency, just sharpness.
The lovely green color and large size of the coils would be a prominant design feature and this immediately suggested an Irish theme for the set. I settled on naming it "The Minstrel Boy" from a patriotic Irish song written by Thomas Moore, reproduced at the bottom of this page. Of course the name also reflects the idea that I expect to listen to music on the set, it will be a minstrel for me. This decision then set in motion the need for other green features, green hookup wire and making a link coil from green magnet wire. Finally a 1N34A diode I bought a couple years back from Dave Schmarder with the green band to cap things off.
The toroid coils have identical features including a primary with 180 uH and a secondary coupling coil with 35 uH. Unfortunately the primaries do not have taps. 180 uH is a bit low for MW work and would require a variable cap with a fairly high top end. I chose three identical 2-gang 270 pF caps tied in parallel to give three 20 - 540 pF tuning. The link circuit consists of two serial 35 pF secondaries for a total of 70 pF, not enough to tune with so I would need to add further inductance. Here is another new feature for me. I made for this set my first honeycomb-style coil, green, of course. I gave the link coil 110 uH for a total link inductance of 180 uH, just as in the primaries. All tune with the three variable caps. Additionally I added a series-parallel knife switch for the antenna circuit capacitance. For my setup the series position will work best, but this will add utility later on. (One green feature I tested and subsequently abandoned was a green LED diode, but even with bias I found it to be hopelessly in-sensitive).