Blimey, has it been this long since starting this conversation?Lots of things got in the way of exploring the techniques discussed by our friend Klaus in his loop antenna videos. But at last, I was able to tinker a little after some discussion on yesterday's LowFER net. Some junk box items were collected together and assembled as follows:
1) length of 14 ga. wire, sufficient to make a loop ~8ft in diameter, used as-is.
2) 2x ferrite sleeve cores, of the same type used to make VLF capable transformers for my long wire antenna. These are a high "mu" material, and about 3/4"long, with a 1/4" bore. Originally intended for suppression on cables, I think.
As a nominal starting point, the ferrites were wound with enameled copper wire (32 ga. or thereabouts) adding a 4 turn primary and 16 turn secondary for a 1:16 impedance ratio. Using a terminal strip, I wired the transformers such that the secondary of one fed the primary of the second, for a nominal 1:256 impedance step-up overall. The wire loop was connected to the primary of the first transformer, and the secondary to the input of a communications receiver using 75 Ohm coax. The setup was entirely contained in the basement radio room, so I wasn't expecting much.
However, the results of this initial test were encouraging. At first it was hard to arrange the wire loop, but once it was opened to a create reasonable area, signals were received. This included WWVB, quite distinct at 60 kHz, and the military transmissions around 20 kHz.
Next steps will be to explore transformer design and different impedance ratios vs. reception effectiveness, as this was literally a shot-in-the-dark "rangefinder" experiment.
Thank you to Klaus for the ideas and inspiration. More on this as I find time to explore.
73s to all,
Ed KO6BLM