Could animal produce less than 700MHz radio waves to communicate ? I don't want those waves interfere with mobile phones and other intercontinental radio communication my space colonists would use. Is it harmful, and could they produce an alternative current powerful enough to produce those waves? Is it exhausting?

Edit: The 700MHz is because I want an alien race using the radio communication I'm talking about would not interfere with space colonists communication, but one day settlers' technology is broken and they decide to use lower frequencies like amateur would do for trans-continental radio communication and then colonists would discover my aliens from the weird interferences.

• What I like most about this question is that the creatures would create interference on that frequency, it would appear to have intelligent connotation, but be unintelligble - not unlike listening to humpback whales singing. At first it would scare the snot out of researchers, who would first believe they'd won the SETI prize, and then realize the signal was coming from RIGHT OVER THERE!
– JBH
Aug 30, 2018 at 2:55
• That is within the range for crystal radios so receiving weill not b that hard.
– John
Aug 30, 2018 at 15:40
• They would need massive eyes to see the radio waves. For 700 MHz, your would need 1.8 km in diameter pupil to see with human resolution, assuming you use something like cones and rods to see. I don't know if they can produce signals like that, though. Sep 2, 2018 at 17:38
• Don't need eyes only electromagnetic sensors like sharks one Sep 2, 2018 at 21:23
• Just a nitpick: if your beings could communicate using radiofrequency, they would make sure that mobile phones would not interfere with those, not viceversa.
– L.Dutch
Sep 4, 2018 at 15:02

### TL;DR

I think it is possible, but not too likely to develop naturally.

Radio transmissions are not a fixed power output. You can have a 700MHz sender with 1MW or 1µW. It mainly changes the range of your transmission, depending on setup.

## What you need

...is something that generates the signal and an antenna. Neither I know of examples in nature, but I doubt it would be impossible.

I just do not see any evolutionary benefit over acoustic communication as this is probably a lot simpler to build that 700MHz communication. And the potential range benefit is not something immediately useful for survival - to make use of that you'd already need a complex social species that could use this to take advantage of the range.
So here on earth for basically every species long range communication is almost pointless. (There are very few exceptions - including humans) However, this is a reason for why I think it did not develop on earth - not that it is impossible to develop naturally.

The signal generation is something it think is more difficult. Sudden electric discharge like eels is not helpful as it is just one-directional discharge and not a rather high-frequency oscillating signal - which is your requirement with 700MHz.
I am not aware of any examples in nature of anything like this, but there might be something.

## Acoustic vs Electromagnetic

Any physical body makes sounds when it interacts with another physical body in some way. Even if the sound can not be heard by us or is incredibly quiet. There is always some sound.
It is easy for an organism that already has a physical body to use this to make sound on purpose as well as use sound to detect objects in its vicinity.

An electromagnetic sender-receiver system has a significantly higher base requirements to be useful for a species. With sound you can imagine organisms detecting and reacting to a sound to gain an advantage. Soon organisms create sound on purpose to trigger reactions by others. That way you can develop something like a communication slowly building it bottom-up instead of top-down like engineering works.

## Bottom-Up vs Top-Down

Top-Down refers to a design process starting with the question "What do I want to achieve?" and then designing a mechanism that somehow achieves what was desired.

Bottom-Up is what evolution does. It starts with something and then randomly builds upon that. Some things work - others not so much. After a long period of time you have developments of entirely different complex systems all looking like they were designed for a purpose to fit in the ecosystem. The truth is that nothing was ever designed. Beneficial alterations had a better chance of making it to the next generation. This means an efficiently working organism exploiting an ecological niché is simply more likely to survive than a less efficient or less focused organism. (Within limits, but that's just a summary)

## Why do I talk about design processes?

Electromagnetic communication as used by humans was designed Top-Down. We built a complex process of signal-generation, encoding, sending, receiving, decoding and interpreting. While it appears similar to acoustic communication, its requirements are a lot more difficult to build in a living organism as well as need a lot more well-adjusted parts.
There is no advantage for an organism having basic versions of electromagnetic communication over significantly easier-to-build acoustic communications - with the downside of significantly lower range.

## The main problem

While I doubt it is impossible to solve the problems of signal-generation and building of an antenna using only biochemistry, I think it is extremely unlikely to occur naturally. The antenna is the simple part. All you need is something with even a slight capability of receiving the 700MHz signal. Even a paperclip works easily if the power output and transmission medium are good enough. Smaller and simpler structures are also possible.

Eels (Credit to @ColonelPanic for the link) are an example of complex electromagnetic mechanisms being used in nature. So it is not too far-fetched that it could be built slightly different to create a signal.

It could be genetically-engineered.
Assuming there is a way to have something like these built into an organism, but it would make no sense to develop naturally, you could - with sufficient sci-fi-level knowledge - theoretically code this into an organisms DNA (or whatever alien equivalent they might have).
Either that or you come up with a really good reason why your species developed a rather elaborate means of long range communication using High-Frequency electromagnetic signals.

I am aware that this answer does not specifically address, how the creatures would develop such a signal, but that is simply because I do not know a mechanism that could work naturally.

I do see a possibility having a burst signal based on biochemical reactions with an equivalent bonding-energy of $$E = h \times 700MHz$$. That way sudden bursts of signals could be transmitted and possibly received. For details you should probably ask RF engineers and biochemists.

However I did feel like OP had some misunderstandings about radio communication and wanted to clear to clear things up a little bit.

On a side note:

If your space colonists use 700MHz and the surrounding frequency-band then they will unavoidably have interference with these radio waves. If they do not use those frequencies, they will not. You can not send multiple signals simultaneously on the same frequency without more elaborate polarity tricks.

Another note:

• This answer is worthy a bounty. I wish we didn't have to wait so much to place them. Aug 30, 2018 at 0:05
• @JBH I honestly do not know. But having seen so many "can trait X evolve naturally" questions being answered with "it already exists in [insert weird animal you've never heard before]" I doubt it is impossible. There might be biochemical reactions with bonding-energies around $E = h * 700 Mhz$ and the communication would then consist of bursts rather than a modulated signal. (OP did not specify, so the realm of possibility is even wider.) Aug 30, 2018 at 6:34
• I fundamentally disagree with your 'main problem' hypothesis. An antenna is nothing more than an impedance matching device. Plenty of non-exotic creatures of developed means to do this, which may not be as efficient as what most people consider an antenna, but by an engineer's definition, would still qualify. And not to nit-pick, but a signal 'consisting of bursts' is still a modulated signal. Without being able to mind-read, I'm guessing you mean something like a poorly designed, BPSK type of modulation. Aug 30, 2018 at 10:33
• And again, not to call you out, but as an RF engineer, I have issues with bad RF information. It is absolutely possible to send multiple signals simultaneously on the same frequency, and this is one of the reasons modern wireless communications has been able to be viable in a world so full of fiber. I don't wish to get off topic, but there are polarity and DSP tricks which will allow for this. Aug 30, 2018 at 10:36
• Another thought hit me: Lightning bugs use electro-magnetics to communicate with each other, albeit at much higher frequencies than the < 700MHz requirements outlined here. While frequencies in visible light range don't usually trip most folks' definition of Radio Frequency, it is the exact same phenomenon. Aug 30, 2018 at 11:22

There is one important biophysical problem you have to overcome in producing such high frequencies: How are you going to produce such signals?

Real-world example

A real-world example for something similar to what you are looking for are (weakly) electric fish, which use electrical signals for communication and prey-detection. In real-world animals which are able to produce such signals (called "electric organ discharge", or EOD for short) of several 100 to 1000Hz (like this one or that one (which actually features an "antenna" of sorts)) the cells making up the electric organ evolved from nerve cells (e.g. the first fish linked, also Electric Eels) or muscle cells (e.g. the elephantnose fish). In both cases the discharges are produced through electrical activity (charged ions (mostly Sodium and Potassium moving into and out of cells) of nerve/muscle cells called "action potentials".

An excursion on weakly electric fish

There are roughly two types of weakly electric fishes: The first, found in Meso- and South America are called wave-type fishes. The name is based on the fact that they continually output a periodic signal. The shape of this periodic signal is distinct to each species, but is preserved across individuals. Individuals differ in the freqeuncy of their EOD and can thus be identified that way. Those fishes have their electric organ cells evolved from nerve cells. They communicate via so-called "chirps", where they briefly increase their firing frequency. They sort-of cancel a period half-way through and begin a new period. Chirps are (among other uses known and maybe unknown) used in courtship behaviour and in aggressive behaviour (mostly male-male). A particular example is that females communicate the exact time of their egg-laying to a male of their choice (who they vetted before), who can then do his part. This allows for example for egg-laying in save, occluded places.

For Apteronotus as a particular example of a Genus of wave-type fishes, in regards they appear to have two different pathways in their electrosensory pathway in the brain - one for prey detection and one for communication. There are even different types of electro reeceptors for the two pathways which encode different kind of signals. Think AM (amplitude modulation) and FM (frequency modulation), only more complex. There's also a third type of electroreceptor, but there is far less research done in this type. Anyway, one of the two pathways is actually split into three areas in the brain. "Pyramidal" cells (named for their shape) in those areas are the first layer atop the receptor cells. Pyramidal cells in the three different areas have different properties. Why? No one knows exactly.

Pulse-type fish have electric organ cells evolved from muscle cells. They don't put out a continuous signal, but just show bursts of activity. I don't know many details about their behaviour.

The problem

Action potentials (electric discharges of cells) take time - a general rule of thumb is that they take about 1ms, which roughly fits the highest frequencies observed. Action potentials which are orders of magnitude shorter are implausible, because cells need to "recharge" after an action potential which takes time, as molecules have to physically move.

Also note that the electric signals have to be read out on the receiving animal's side. Using receptor cells we know, for the same reasons as above, there is no way that you can get more information out of a 700MHz signal that out of a much lower frequency signal unless you are willing to have a humongous number of receptive cells. While it is possible for cells to encode signals which are faster than their firing rate (number of action potentials per time), the required number of cells gets larger and larger that higher your frequencies become. The brain of the electric fish already has dedicated huge areas just for electrocommunication and electric detection of prey. The size of those areas would have to increase many times for signals in the area of 10⁸Hz.

I hope that this is somewhat understandable for a lay person. If it is not, feel free to ask and I can elaborate on it, and also provide sources for the claims above.

tl;dr: It's certainly possible at lower frequencies, but likely not at the frequencies you are looking for.

• There's something I don't understand: this is SLF and it's said on wikipedia that it's very difficult to build SLF transmitter, how could fish do that ? Sep 5, 2018 at 11:45
• I believe this stems from the fact that SLF/VLF as used e.g. for communication with submarines more complex messages are to be encoded in the signal. Whereas in electric fishes there is not much neccessity to deliver complex messages. The animals can just use a repetitive discharge (which also isn't a perfect sine wave, which is I believe another constraint on SLF communication) and communicate by simply disrupting their pattern. For detection of other animals they use the interference which always happens with electromagnetic waves of different frequencies. Sep 6, 2018 at 8:05
• So my aliens would talk like birds with rhythm mostly and slight frequency modulation I think. Sep 6, 2018 at 15:54
• Yeah, I think that's a good way to think about it. Sep 10, 2018 at 7:14
• Repetitive discharge can be a perfect sine wave or not. And the modulation type often (for the sake of argument I won't say always, but....) does not have any constraints on whether a 'perfect sine wave' is used or not. One is the frequency of the transmission, the other is the form of modulation. And in your TL;DR: seems to miss the point that the author is only looking for frequencies lower than 750MHz (nothing specific). This could be say 175Hz as posted in my answer. Sep 13, 2018 at 10:33

It's not only possible, but most of the requisite pieces have actually been developed in nature already.

Allow me to introduce you to the Spark-gap Transmitter, the earliest means to transmit RF energy. This requires turning on/off an AC source of power, which we could easily imagine as any number of electric fish. Whether or not these species are intelligent enough to use this as a sophisticated means of communication may be in doubt, but there are plenty of examples of species who would be. And even something simple as "I'm being attacked" could be of benefit to the species and effectively be a form of RF communication.

As for the receiving end, in RF theory, this works exactly the same way as transmitting. But for biological/evolutionary sake, let's say that this was developed first, such has already been discovered in a number of species. These two functions have developed separately, but there is little reason to believe that they couldn't be developed in the same species.

As for frequency, yes, it will make a lot more sense to use low frequency. This will allow for longer transmission distances (as a rule of thumb, there are other factors involved) at lower power levels.

Roughly 60W at 175Hz could make for a rather robust transmitter. And this is for a species evolved for different purposes. I'd imagine a species which received benefit from the communication you suggest could transmit with even more power.

Oh, and I should mention that this all works much better outside of water, especially sea-water. You didn't mention any details about your creatures, but free-space transmission (effectively in air, not water) is much more believable.

EDIT: In my haste to post the above, I forgot to mention that this species actually does something very similar to what you are asking. I wouldn't quite call this a form of communication (if your definition is between two hosts), but it clearly demonstrates a biological niche which can be filled through RF transmission and reception. As the required biological 'hardware' is already there, expecting the 'software' to never be able to exist is a fallacy in my opinion.

• The Original Poster said they do not want interference with other communication. The spark gap transmitter plays anything but nice or constrained to a specific band. :-P Sep 4, 2018 at 12:09
• Nothing in my posting suggests that there would be interference at the 750MHz levels. MHz vs. Hz ;) Sep 13, 2018 at 10:29

I think sharks "use" something similar. They can sense the electric current in the nerves of their prey when it moves its muscles. I think water is more suitable transferring these signals than air, but maybe it works if animals evolve to transfer signal intentionally and can increase the transmission power.
https://en.wikipedia.org/wiki/Electroreception

• Transmission distance for RF will almost always be worse in water (and salt water is even worse) than in air (which is so good, it is often considered to be a vacuum when calculating loss). This has to do with conductivity of the transmission medium along with a few other factors. Interesting enough, RF 'wave guides' can be created above salt-water, allowing energy to propagate much farther than even in air alone. RF is weird :) Aug 30, 2018 at 10:50
• Sharks (or better their organ) just receive. It does not transmit.
– L.Dutch
Aug 30, 2018 at 10:58
• Yes, but give the poor prey fish also the same organs as sharks have to receive these signals, and the shark, rushing to its target under full muscle power (and thus full activity in their nerves), will do the rest Aug 30, 2018 at 11:00
• Note that the signals we are talking about are around 10 Hz, not 700 MHz. Transmission distance for RF for extremely low frequency is excellent under water (it is used to communicate with deep submerged submarines). Aug 30, 2018 at 14:13
• I am not a biologist but as far as i know neurons can change their state at rates as high as 1kHz, and OP asked for frequencies lower than 700MHz. Admittedly 1kHz is not even enough to transmit human language, but still... Aug 30, 2018 at 14:23