Hi Paul,
It's to early to start an ULF experiment between me and you. But some
preparations could be helpful. How do you estimate the sensitivity of
your RX system on 2970 Hz? Is the spectrum clean or do you suffer from
Mains QRM? Did you already put some attention to this band?
73, Stefan
Am 08.06.2016 11:15, schrieb DK7FC:
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
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