This is more than interesting. I have been reading on this a little, but most is for GHz. I am wondering about HF, MF and LF QRP.

And the lower VLF bands. Easy and common communication thru mountains and water is intriguing.

Anyone fooled with this before?

https://phys.org/news/2019-04-slac-compact-antenna-radios.html

 

This is more than interesting. I have been reading on this a little, but most is for GHz. I am wondering about HF, MF and LF QRP.

And the lower VLF bands. Easy and common communication thru mountains and water is intriguing.

Anyone fooled with this before?

https://phys.org/news/2019-04-slac-compact-antenna-radios.html

Looks more like near-field electric induction than far-field EM wave propagation.
https://en.wikipedia.org/wiki/Near_and_far_field
The physics of antenna radiation resistance into free space vs physical size sets hard limits on em wave efficiency even for a dielectric resonator antenna.
https://en.wikipedia.org/wiki/Dielectric_resonator_antenna

I used VLF stations all the time back in the 70's for fleet broadcast message reception at sea.

https://en.wikipedia.org/wiki/Naval_Communication_Station_Harold_E._Holt
https://en.wikipedia.org/wiki/Lualualei_VLF_transmitter

 

You remind me of the experimentation we did in the unlicensed 1750 meter (~160kHz) band when I was a kid. We didn't have much luck but we managed a couple of miles.

I'm tempted to try again.

https://www.lfengineering.com/lf-vlf-communications.cfm

 

You remind me of the experimentation we did in the unlicensed 1750 meter (~160kHz) band when I was a kid. We didn't have much luck but we managed a couple of miles.

I'm tempted to try again.

https://www.lfengineering.com/lf-vlf-communications.cfm

The results in the actual paper mirror what I thought about near-field induction effects and antenna radiation resistance.

https://www.nature.com/articles/s41467-019-09680-2

In addition, a portable system open to the ambient environment is used to measure the electric and magnetic field versus range (see supplementary Fig. 7). Input lead lengths and effects from RFI are minimized. The magnetic field drops off as 1/r2 and the electric field drops off as 1/r3 as anticipated in the electric dipole near field (see Fig. 8). We have separately confirmed that the magnetic field continues to fall as 1/r2 to >80 m. A fit to the electric field data gives the measured value of dipole moment, 7.5 mA-m. Discrepancies between the measured and calculated dipole moments occur due to effects of nearby structures, deviations of the resonator from an ideal dipole, and drifts of the Q during operation.

https://static-content.springer.com/esm/art:10.1038/s41467-019-09680-2/MediaObjects/41467_2019_9680_MOESM2_ESM.pdf

 

The frequencies are not getting enabled through the module and by the post we can see that the issue needs to be fixed. The main thing is that we have to know the basic aspects of this before implementing.

 

It looks like a sine applied to rod. Then a capacitor at base of rod is switched in and out at base band rate.

FSK at antenna.

 

It looks like a sine applied to rod. Then a capacitor at base of rod is switched in and out at base band rate.

FSK at antenna.

A fancy spark transmitter or a Alexanderson Alternator with fast frequency control.

This DAM system is a cool proof of concept but we already know a lot (since at least 1906) about actual VLF transmission engineering. All of the generation technology can be miniaturized but the physical antenna for far-field wave propagation can't.

 

This DAM system is a cool proof of concept but we already know a lot (since at least 1906) about actual VLF transmission engineering. All of the generation technology can be miniaturized but the physical antenna for far-field wave propagation can't.

We'll just use (waves hand) nano-fractal antennas with huge exposed edges in tiny spaces.

Capture? Don't bother me with details, I am trying to get round one funding.