How to design antenna below 1khz with antenna design software like HFSS?

[youta556]

Usually,HFSS,antenna magus can help to design antenna above 1khz.
What can be used to design antenna below 1khz?

[cdev]

Well, you may be able to use NEC, or something similar, (I don't know) but your antenna is going to be very large, very very large. Youre going to have to face that fact.

As far as software, with some limitations, (propagation effects) you may be able to simply scale the proportions of the various elements for the lower frequency. As said elsewhere, get ready for large size.

Do you have a fairly large plot of land (or a small to medium sized country) to site it on?

[Bud]

You already have two of them, with built-in directional tracking. They are called ears.

[TimFox]

The US Navy maintains a very expensive radio transmitter (NAA) operating at 24.0 kHz, formerly 17.8 kHz, with 2 MW power.
https://en.wikipedia.org/wiki/VLF_Transmitter_Cutler
The use case is communication with submerged submarines (not very deep).
The antenna takes up roughly a square mile.

[MarkMLl]

"What the large print giveth, the small print taketh away."

And I have to ask why OP insists on yelling at us with print which is both large and emboldened.

MarkMLl

[cdev]

I hope you see that I am trying to be reasonable. After all we're all here to learn. An antenna that is anything even remotely efficient at 1 Khz ia going to be large. Really large. Consider that light travels 186000 miles per second. So, a quarter wavelengh monopole is 1/4 of that!

Maybe you could use the mythical space elevator as your monopole? If its made of graphene and carbon nanotubes, they are conductive. So that might work. If you could get it to be an acceptable impedance.  And then match to it. Sounds a bit like the problem of using a big tree in the tropics as a HF antenna..

So, how would 1Khz signals propagate? Quite some time ago I helped build a database that stored info about the science of things like this. Its still in service and quite useful for such speculation  Consulting that it seems that VLF signals are very unlike HF signals and interact with the Earth and its magnetosphere in a great many ways. .

[max-bit]

With such low frequencies, not only the size of the antenna is a problem, but also the interference from the power grid.
For such a "huge" antenna, you not only need a lot of space, but also a significant distance from all buildings.

[coppercone2]

I would say you are not able to build this antenna because of environmental and financial reasons. The only reasonable way to get this long a emitter is to use the earth.

https://en.wikipedia.org/wiki/Ground_dipole

There might be privately funded oil company or mineral company exploratory antennas made like this that run at frequencies near 1KHz. Maybe with the oil problems its not a bad idea to try to get government approval for a organization to research this.. but IMO just get more solar panels instead of fiending for oil.

The only reasonably low cost way to try to make a conductor that long is to try to make a partnership with whoever might own a rail road and modify that to make like a loop antenna out of steel, but its still not easy since its not a good conductor and the skin depth of these frequencies means you can't just flash plate copper on stuff. Even with a good antenna you would need a substantial power plant...

I wonder what you could do with the earths molten core in a few thousand years when we can maybe dig down there.

I also suspect that since this is useful for nuclear war and also oil (which many seem to blame as a cause of the major wars in the last 30 years), that simulators are highly proprietary and guarded if they exist. People want their oil contracts and submarines to be safe. the movie "there will be blood" comes to mind in regards to oil industry having a "private security apparatus" protecting it (its seriously greasy)

https://en.wikipedia.org/wiki/Ultra_low_frequency


Another way to make an actual antenna for this might be to use a extremely powerful laser shot into space so that it ionizes air and makes a conductive path.. but I am not sure how powerful that would need to be, or if you can make such a long conductor easily without blooming.

https://ieeexplore.ieee.org/document/9647683

more like JJ abrams lol. TLDR : It says to like shoot a rocket that makes a exhaust stream that is then ionized with a laser to reduce laser power requirement.. so you only need a still day, a rocket and a big laser. This is refereed to as an 'ionization channel'.


https://www.sto.nato.int/publications/AGARD/AGARD-CP-529/AGARDCP529.pdf
Here is a treatise on low frequencies in general.

[TheMG]

The US Navy maintains a very expensive radio transmitter (NAA) operating at 24.0 kHz, formerly 17.8 kHz, with 2 MW power.
https://en.wikipedia.org/wiki/VLF_Transmitter_Cutler
The use case is communication with submerged submarines (not very deep).
The antenna takes up roughly a square mile.

Found a very interesting presentation about that:

https://limarc.org/wp-content/uploads/2020/04/VLF-Presentation.pdf

Very impressive antenna system needed to achieve 74.9% radiation efficiency at these frequencies! Would likely cost BILLIONS to build something like that from scratch nowadays.

Now imagine the challenges at 1kHz, a whole order of magnitude lower in frequency! Any antenna that you can make for such low frequency without significant real estate and deep deep pockets is going to be very very inefficient. If you're putting out 1000W transmitter power and getting even 0.1W EIRP out of it at 1kHz, you're doing amazing!!!

[cdev]

You already have two of them, with built-in directional tracking. They are called ears.

This is very interesting stuff to know about. The Earth rings with VLF. Its not man-made. Its natural.

[TimFox]

You already have two of them, with built-in directional tracking. They are called ears.

For air pressure, at 1 kHz, yes. but ears cannot sense electromagnetic fields. as far as I know.

I have no experience with 1 kHz EMF into ears, but there is an interesting effect found in high-field MRI magnets.
The fluid in the inner ear is conductive, and will feel magnetohydronamic force when the head moves inside a 15 or 20 kGauss DC field.
Unfortunately, the signal from that effect to the brain is inappropriate for the human balance mechanism, and the result can be serious nausea or vertigo.

[cdev]

Just found on Google. Animals that sense Earth's magnetic field include sea turtles, birds, fish and lobsters. Sea turtles, for example, can use the ability for navigation to return to the beach where they were born"

Salmon too have an ability to find the streams where they were born and travel up them. This makes sense as a survival strategy.

Never underestimate Nature.

I have seen (relatively) big salmon attempting to travel up really tiny "streams". Its really something to see.

Animals' magnetic 'sixth' sense may come from bacteria
The question is one that has been unresolved despite 50 years of research!
https://www.sciencedaily.com/releases/2020/09/200914112224.htm

[hagster]

The OP asks about designing a 1khz antenna not building one. I see no reason HFSS, NEC, OpenEMS other tool can not be used to design such an antenna.

[cdev]

No reason not agreed. Think big!

[RoV]

a transmit antenna is hard, but a receive one is well feasible: take a ferrite cylinder (as large as you can) and wind many turns. Then resonate it and apply to a low noise amplifier.
Regarding the question of HFSS or similar: as long as you avoid nonlinear materials, I suppose you could do the design at e.g. 1 MHz and then scale it.

[coppercone2]

www.vlf.it has good low frequency antenna designs

[TimFox]

www.vlf.it has good low frequency antenna designs

One posting there   http://www.vlf.it/sos-enattos/sosenattos_live.html  is about sensing magnetic fields at extremely low frequencies (< 100 Hz, down to < 1 Hz), but I don't think that the sensors qualify as "antennas", which respond to radiated waves.  Rather, they are "coils" that respond to oscillating magnetic fields that are not radiating.

[coppercone2]

I figure on earth they are synonymous with antennas when frequency is low enough, but you are right that for 1KHz which is 300km, you can get into far field on earth (but can you because of the curvature? horizon is 20 miles, so you would need to know how they propagate)

Also it needs to be said to be careful with low frequency transmitters, because power lines communications use them (if you did manage to make something (styropyro laser antenna?, careful that the electric company does not confiscate death star) ).

https://en.wikipedia.org/wiki/Power-line_communication#Long_haul,_low_frequency

[coppercone2]

Well it might be space related, there is no reason why a satellite cant unfurl a long dipole or something. No one said its terrestrial. Might be a good materials test to help encourage development of a space elevator.

[A.Z.]

and then, also see

http://www.grahn-spezialantennen.de/

[T3sl4co1l]

Not really anything to design, it's fractional wavelength, electrically short -- just make a loop as big as you can afford, then match that to 50 ohms or whatever with a suitable transformer, or coupled loop, or matching network.  Make it resonant to get higher gain at very narrow bandwidth, or ignore the reactance to get very low gain (and radiation resistance) over whatever bandwidth you like.

Conductor size: also as much as you can afford.  Litz an option (pretty coarse at these frequencies, a bundle/multiconductor cable of stranded wire would do quite nicely).  Reduces electrical resistance, making radiation resistance a larger part of the total (so, increasing SNR; but still much, much smaller than reactance, unless you tune it out).

Use balanced designs, or shielding, to give immunity from local fields (typically of the opposite type, i.e. an inductive loop with E-field immunity, or electrically-short dipole with H-field immunity).

Tim

[TimFox]

As pointed out above, with very, very short antennas the series reactance is much higher than the radiation resistance and needs to be tuned out.  Unfortunately, with practicable loading coils the ESR of the coil will still be mucy higher than the small radiation resistance and the resulting SNR will suffer.

[A.Z.]

As pointed out above, with very, very short antennas the series reactance is much higher than the radiation resistance and needs to be tuned out.  Unfortunately, with practicable loading coils the ESR of the coil will still be mucy higher than the small radiation resistance and the resulting SNR will suffer.

still you can build a ferrite sticks loop which, with the help of a tuning cap will allow to go pretty down in frequency, while retaining a manageable size; an example of such a VLF antenna is here

http://www.vlf.it/etna/etna_live.html

not easy to put together, but doesn't require several acres of land, either; then, by the way, the antenna is just one component of the receive chain, it's important, sure, but if what comes next isn't up to the task...

[geggi1]

What are you trying to do with the antenna is the most important question.

If i where playing with antennas for these low frequencies I would start building something and then when its start to work test the design with a antenna sim software.
Most likely there will be factors not implemented in these softwares that is relevant for low frequeicies.


On these low frequencies you will have to make some kind of loop to keep the cost and size at a sensable level.
If the atenna is going to be used for reception things can be a bit simpler than for transmision.
By using a ferrous material (ferrite and powder iron cores) you can reduce the size of the antenna a lot.
The premability material of the core will be the factor reducing the size and number of turns of the loop compared to a air core. You can probably start to look at the types of core material used in switch mode power supplies or RFI prevention at low frequencies.
The efficancy of the antenna will be low, but that can be compansated by using more gain in the reception equipment. Look at how its done on VLF reception and earth reception with high gain instrument opamps and sound cards.

For transmition you should probably start to look in to electro magnetics and transformers.
The simplest rout for this is probably to make a reasonable large multi turn loop tuned with a bank of switched capacitors.
If you manage to get the impedanse of the antenna to be in the range of 4-8 ohms you can use a audio amp as the transmisioon aplifier.

For gnerating signals for the transmision there are a lot of digi mode ham software that can be usable. The same is also relevant for reception.
Modes like WSPR and FT8 is a good place to start with software.

[MarkMLl]

still you can build a ferrite sticks loop which, with the help of a tuning cap will allow to go pretty down in frequency, while retaining a manageable size; an example of such a VLF antenna is here

I was wondering whether a ferrite rod or manageable loop would do the job, but was reluctant to comment lest OP's mention of Antenna Magus implied that he had his heart set on an E-field design.

At a somewhat higher frequency, but http://www.creative-science.org.uk/MSF3.html (and related pages) might be worth mentioning.

MarkMLl