This is an interesting one as I went into the pound shop today to get drinks (they're on any 3 for £1 right now), and after spotting two distinct size of cans, the "energy drink" size (though they had some with non-energy drinks in them) and the usual size cans I remembered what had been done by Alex PY1AHD, the creator of the AlexLoop WalkHam (of which I can't afford right now), it is interesting how something not entirely related to radio can bring you back to radio.
What Alex has done, and is somewhat well known, is make a magnetic loop with a variable capacitor using two drinks cans of the normal size and two of the thinner size. with the two slimmer cans attached to a piece of PCB which in turn is mounted to a mechanism to allow movement by way of 2 syringes and a hose filled with water, the loop is made from coax and appears to be terminated using PL259s and SO239s, in turn to the top of the non-moving cans, his choice of cans were of a well known brand of cola, though other soft drinks cans should work the same, my theory is to try and replicate the capacitor and see if it works, though there is no mention of any insulator inside the cans to separate the "plates", it could quite simply be the air, but all of the parts are easy to obtain, cans are pennies, coax you could have lying around some spare (I don't as all of the coax I have that would be ideal is used as feedline already), or you can get it cut to length, PL259s and SO239s you could already have also, I have a few but have earmarked a square chassis mount SO239 for other use), blank PCBs are also affordable.
I have all the cans and have finished the drinks off, all I need to do is get started making the capacitor and see how it fairs, and importanlty if the capacitance is right for 12-10m as it is this portion of HF (including 11m) that I can use with the equipment I've got
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