8 Jun 2013

Playing with a ferrite rod at VLF

Just for amusement, but with a slight hope it might work, I tried resonating a LW ferrite rod coil (about 3.5mH) at 8.97kHz to see how it might perform as a miniature portable receiving loop in my earth-mode tests.

To test other antennas and VLF preamps, I first connect my 8.97kHz 5W transmitter into a resistive dummy load and check that I can detect the signal strongly some distance away locally (about 10m away only). The emissions from the cables are such that this gives me around 30-40dB S/N on Spectran with the usual settings on my 80cm loop. Switching over to the ferrite rod RX antenna it was hard to tell if a signal was there at all.

So, that's one experiment I'll close and report as a failure. Had it worked, even 10s of dB down, it might have made a magnetic field antenna that could have been deployed mobile. You may recall I tried /M on 8.97kHz a few months ago with my 80cm loop strapped behind the car, until someone pointed out this probably would have invalidated my car insurance and I stopped.  I had vague ideas of dropping the VLF resonated ferrite rod close to the ground behind, somehow fixed from the rear bumper.

Ho hum, another idea bites the dust.

1 comment:

Anonymous said...

think its because the L/C ratio is too high - hence magnifiction factor low.