Hi all,
I've got a first result with my ULF project: One of the ideas to
generate and radiate a signal on the 100 km band to use a ferrite power
transformer with using two E cores out of N27 material. These are
available at https://www.buerklin.com/de/e-kern/p/83d970
At 2970 Hz i can apply 1 V / turn without saturating the core, maybe
even more. I think i can generate 3 kV (rms) with one transformer
without a risk of a flashover. And i can set an air gap between the two
E cores.
For 2970 Hz i need L = 6.1 H! Now without an air gap i need about 800
turns (hand wound!)to resonate the antenna. So i can apply 800 V now.
On 2970 Hz, my antenna radiation resistance is 70 uOhm. With 800V on the
wire it radiates 6 nW!
The distance to my remote site is 3.5 km or 0.035 lambda.
I'm TXing since last night and got a trace of up to 15 dB SNR in 424
uHz. Quite weak but it's a first step.
The signal was radiated with an E field antenna and received with a H
field antenna, so there could be a better result in the near field.
I' now planning to wind more turns on the transformer and add an air gap
to keep the inductance and rise the voltage limit.
73, Stefan
1st_trace_on_the_100km_band.jpg
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