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First trans-Atlantic contact made on 432 MHz (ei7gl.blogspot.com)
424 points by lightlyused 11 months ago | hide | past | favorite | 127 comments

For some context on why this is interesting: since the dawn of radio, we've known that relatively low radio frequencies (up to maybe 30MHz, depending on time of day, solar activity, and other factors) can propagate for very long distances, by following the earth's surface or bouncing off the ionosphere. This is why a portable shortwave radio can pick up radio stations from the other side of the world.

Higher frequencies don't benefit from these effects, and generally don't propagate beyond direct line-of-sight. But in rare circumstances, atmospheric refraction can cause high-frequency radio signals to propagate much farther than normal, which is what seems to have happened here.

On a technical level, this radio contact was made possible by the recently-developed FT8 digital modulation scheme, which is designed to transmit a minimal amount of data (basically just a pair of callsigns) at only a few bits per second, so as to make even extremely weak signals detectable. The "dB" column in the screenshot illustrates that the received signal strength was roughly 100 times weaker than the background noise.

> But in rare circumstances, atmospheric refraction can cause high-frequency radio signals to propagate much farther than normal,

My uncle, decades ago, was a cop in rural Ontario (based on Kilaloe). Absolute middle of no where, mostly rural, but an area with a bit of elevation here and there.

Somewhere down in the US, Virginia I think, used the same frequency as them for their police radio. They discovered this because every now and then if you were up on a hill under the right weather conditions, they could talk to each other, hundreds of km apart. Very confusing the first few times.

Or so he tells the story. I'm neither a cop nor a person familiar with the magic of radio technology.

It is quite possible. I used to use packet radio on 144.45MHz, and when the conditions were right I could reach a BBS ~200km away. That's not terribly exciting, but both stations were pretty low to the ground, not very powerful or directional, and definitely not in line of sight.

For reference, according to wikipedia, if one station was at sea level and the other about 1500m above, you'd expect line of sight to be around 160km.

Similarly, around the same time of year (January or so) but less frequently we used to get VHF TV interference from a station on the same frequency but more like 1000km away (if I'm remembering the source station right, it was a long time ago), strong enough to interfere with the more local transmission.

Radio+atmospheric effects can get weird.

If it was low-band (30 to 50 MHz) police radio, it was most likely sporadic E propagation.


It’s episodic and well known phenomenon to any amateur radio operator that prefers the vhf/uhf bands.

One summer afternoon I was walking in the woods with a 2 meter handheld (140-144 MHz) and made a contact on somebody 200+ miles away across Lake Ontario (and land.) He was a Canadian who enjoyed tropospheric propagation events across the lake, particularly tuning into the My Network TV station in Syracuse which has an absurdly powerful transmitter.

The indicated FT8 signal to noise ratio is very misleading. The calculation is based on a noise bandwidth of 2500 Hz, yet the FT8 signal is only 50 Hz. The actual minimum signal to noise ratio of FT8 is around 1 dB in 50 Hz (-156 dBm in a gaussian channel with a perfect 0 dB noise figure receiver), which is consistent with a 1/2 rate LDPC code like the one FT8 uses.

Thank you! Was just about to point that out too. Drives me nuts when the standard SSB bandwidth is used.

People transmitting 100W on HF with WJSTX modes is another pet peeve.

100W FT8 bothers you? There are people pumping 1500W on FT8. I would get the sentiment on WSPR though.

I run 100W, and I'm rarely picked up above -7dB. Some of us have to given our QTH, antenna, and where we're trying to reach. Not all of us are in it for QRP. Perhaps they should designate a part of the FT8 bandwidth for QRP? 73

I don't get the hate for 100 Watts on FT8 either. Use the power you need to make the contact. Keep an eye on the waterfall to make sure you aren't doubling.

If you're getting a +5 SNR report then obviously dial it way back but when I do DX at 100 Watts it's usually -10 or less.

Of course that's for QSOs usually well over 3k miles.

Isn't 50W that is max allowed power on UHF (432MHz) for amateur radio ?

de R9LAJ

Sorry for the late response. Yes you're correct, 50W max on that band, at least in the US. I was replying to a person referring to FT8 on the HF bands where the max power is 1500W. 73

> Higher frequencies don't benefit from these effects, and generally don't propagate beyond direct line-of-sight.

Interestingly, and perhaps you already know this, but the distance radio waves travel is actually a bit farther than line of sight (even at higher frequencies like UHF):


> ... the received signal strength was roughly 100 times weaker than the background noise.

Okay, this sniped my curiosity. Where can I read more about the math/physics that makes this possible?

Apart from the cool story about error correction, in general detecting a signal that's weaker than background noise is something we do in statistics all the time.

If you have big enough samples, you can tell a normal distribution with mean 0.01 apart from one with mean 0, even if their standard deviation is both 1000.

Error correcting codes are in some sense a very cool and efficient way to get the equivalent of that bigger sample.

(You could also just send your signal many, many times. But simple repetition is a vastly inferior solution to the ingenious codes people came up with.)

Error correcting codes are certainly a part of it (from simply looking up the definition of FT8), but what can also help generally is knowing very specifically the frequency range of your signal so that you can filter out the out-of-band noise. A lock-in amplifier is one example of this: https://en.wikipedia.org/wiki/Lock-in_amplifier

In college, we had a class called "Detection Theory", which handled this topic - and was required for people that studied signal processing / telecom / telemetry / remote sensing / etc.

Here's a quick wiki link for that topic:


search error correcting codes. turbo codes. Viterbi codes. Golay codes. Reed-Soloman codes, Gallagher codes... the list goes on.

Basically, error correction can supply “coding gain”. So in the path-loss equation, you get to add gain for error correction.

In the above case, if the signal is 100 times weaker than the noise, you need a code with 20db of coding gain to reach break-even, if that makes sense.

I think in addition to all the other replies, a key in how this happens on more of a physics level is how spread spectrum communications work. In short, it’s a technique to ‘squish’ a high-amplitude, narrow bandwidth signal down to a low-amplitude, wide bandwidth signal. The resulting low-amplitude signal can be lower than the background noise. Look at Fig. 6 here: https://www.maximintegrated.com/en/design/technical-document...

The general field of signal processing - in particular to pulling data out of noise there are error-correcting codes, algorithms like Viterbi and putting them together let's you pull off pulling data out of noise, really signal from interference. There's an entry for FT8 on wikipedia that I haven't digested but it has some other starting points.

As to the physics there's also the fact that the phenomenon that creates a good transmission line between participants is in flux and you have to get your data through while the transmission line passes enough signal that the receiver can decode it.

To add to the things that make this possible. Take a look at DSSS or signal spreading.

This is a method of spreading the power of your transmission over a much wider part of the spectrum. Hence, this doesn't help much if your transmit power is limited. However, it does help if your transmit power per slice of bandwidth is limited.

This is used for a few methods. The first is spectrum-sharing (which requires orthogonal codes). The second is detection avoidance (lower power per bandwidth makes it much harder to recognize the signal unless you already know how to de-spread). The third method is to avoid 'point noise sources' from blocking your signal. E.g. a wifi burst of 1MHz might drown out your signal if you use 1Mhz of bandwidth. But if you use 10 MHz, it only blocks one tenth of your signal.

100 weaker is not yet a limit by far. GPS can be 10000000 times below the noise floor, and some advanced system may take it even further

I never understood why most GPS receivers seem to only use 1 bit ADC's. Surely you're just making the already hard problem harder for yourself by adding a massive amount of quantization noise?

GPS is a very old system. I think just a lot of GPS IP has been used as copy and paste since, without much rethinking.

1-bit ADCs make the initial correlation processing easier and cheaper.

The Deep Space Network is capable of communicating with the Voyager probes 100s of AU from earth with so little signal it’s incredible

The term you're looking for is Forward Error Correction, send extra bits so you can lose a few along the way.

That takes care of lost information, but how do you reliabiliy filter out signal from noise? Can a simple FIR filter work in this situation?

FT8 syncs everyone's clock on 15s intervals, you can also send well known sequences at the start of a transmission and search for those.

FIR filter alone cannot do this, but combined with special coding like Direct Sequence Spread Spectrum (DSSS) does it pretty well. For example, CDMA and GNSS benefit from using DSSS.

More accurately, extra bits are added to the transmitted stream so that bit errors in the received signal can be corrected.

See also: information theory and channel capacity

From TFA:

> The most likely mode of propagation was marine ducting with the signal being trapped close to the ocean.

> There is a whole truckload of Sahara dust getting across the Atlantic this week. I blame it for the modification of the normal atmosphere into a superrefractive one, supporting communications for the first time on this band. Sahara dust dryes the air around it by absorbing moisture and thus modifying the refraction index. Like a G-Line feeder or an optical fiber, the difference in refraction index between different layers allows the propagation path to curve down following the Earth curvature to allow these fantastic QSOs.

> I read about this phenomenon many years ago in an old ITU Bulletin justifying the enhanced superrefraction conditions usual between Cape Verde and the Western African Coast.

> Jose, CO2JA

From you:

> this radio contact was made possible by the recently-developed FT8 digital modulation scheme

My questions:

1. which factor was more important, or were they equal?

2. Is it COVID related? ie, atmospheric conditions are suddenly different around the world due to shutdown of industry.

IANA Radio Engineer

1. Both; perhaps the dust

2. No


I've worked parallel to a whole bunch of radio obsessed electronic engineers; they get really excited about atmospheric conditions, and they regularly use weather maps to win competitions with unusually long transmission ranges (- a whole bunch of mad people across England / Europe / etc. go out on the same day and try and make as many contacts as possible. The team with the most unique contacts wins).

1. I don't think you can quantify the two in equal units such that they can be compared - they both played a part.

2. Probably not or at least not significantly. Ducting occurs frequently and Saharan dust is blown out to sea every year. Note that 'for the first time on this band [at this distance]' is more accurate.

Have we started looking for modulations like this with SETI? A signal would have to be quite loud to be ordinarily detectable, but someone might embed e.g. digits of Pi into an ultra-wide spread spectrum transmission that could be detected even though it's far below cosmic microwave background.

These modulation methods require knowledge and synchronization of coding by both receiving station and transmitting station. Without knowledge of the sender's modulation schema, the received signal appears as noise.

Indeed, more and more of the Earth's electromagnetic radiation will be designed to be indistinguishable from noise. Or it will propagate in optical fibers. Based on our own experience, I give a civilization a roughly 100 year period during which their radio emanations will be intelligible. A planet interconnected by optical fibers is kind of a poor man's dyson sphere. ;-)

Yes. Some years ago I went to a talk on SETI at Stanford, where they talked about detecting "carriers". Anything they could detect is obsolete technology now. Analog TV was 80% carrier (video was AM, the audio part was FM) with a huge sine wave component. Digital TV looks like narrowband noise.

Analog TV was probably Earth's biggest detectable RF export. Lots of transmitters in the megawatt range transmitting 24/7.

I think technological progress in modulation might be a really good explanation for the "great silence." Advanced aliens could be all over the place, but if they're really advanced their transmissions are low-power, directional or cellular, and look like noise if you don't know the codec.

I thought I remembered reading somewhere that even our most powerful emissions were unlikely to be detectable to any type of receiver we could conceive of further than a light-year or two, less than half of the distance to the nearest star.

I believe the answer is yes. One example would be the use of the Karhunen–Loève transform [1] promoted by Claudio Maccone [2].

[1] https://en.wikipedia.org/wiki/Karhunen–Loève_theorem

[2] https://doi.org/10.22323/1.056.0034

I am not sure I understand, it doesn't seem to be the first transatlantic contact made at a frequency above 30Mhz. (e.g.[1])

So what makes this historical? That it was never done at a frequency as high as 432 Mhz?

[1] https://ei7gl.blogspot.com/2019/06/historic-trans-atlantic-c...

I wonder if reduced air traffic contributed to the success? I.e. could it be that favorite conditions are not that rare if not due to disturbance from all the flights?

I would say the opposite - UHF signal can bounce from plane traces, this effect is known to be used by some UHF radio amateurs to conduct long distance (beyond the line of aight) QSOs.

I suppose I get why this is interesting. But I don't get why it's useful.

If no one would ever really be using this mode/frequency to communicate long distances given this was such a special circumstance, and HF is already the standard (I understand), what practical has been achieved? What is this for?

First of all, This website is called “hacker” news: practicality doesn’t have a lot to do with it. [1]

Second, practical research into how to transmit information more efficiently has many, many applications. WiFi and mobile-phone technologies would not exist without research like this. [2]

[1] https://en.wikipedia.org/wiki/Hacker_ethic

[2] https://www.nsf.gov/about/history/vbush1945.htm

Think of this as a sport like marksmanship or hot air ballooning. There exist much easier ways to make a hole in the middle of a piece of paper, or to get from a fixed location in one corn field to a random one in another, but sometimes the challenge of a more elaborate process can be more fun. Particularly if no one has done it before, or done it as far with as elaborate or as simple a machine as yours.

I guess ham radio enthusiasts are easily offended when you ask them practical questions that they don't have a good answer to.

So, I don't care about ham radio at all, but I can imagine that if you do something for fun that it's grating to have people ask you over and over again "What is it good for?" What is anything good for? What is flying kites good for? What are walks on the beach, or sunsets good for, or any of the other purposeless activities that people engage in?

It's fun to do something that nobody has done before. Even though I don't care about the actual goal, it's interesting to read about what the obstacles are, and how people overcame them.

Well, that's a legit point. And I won't pursue this topic much longer (tiring to talk meta about threads).

But equally, if someone is sensitive about being asked what's it good for, then maybe don't seek worldwide attention for it on the front page and get offended when the world asks you such questions.

And to add to this, if it's a technical/experimental thing you're doing, you never know; you might discover/learn something useful.

Do you think a generalization like this is in any way constructive?

Also I don’t see any reply that I thought demonstrated “offense”. Perhaps it was deleted.

I was just reacting to my post with a legitimate question being severely downvoted. And I do think a question about whether something is useful is a legitimate question, whether the answer is yes or no. Some people must be offended, based on being downvoted -- but who knows when there's 1000s of users. You can't waste your time being offended on the internet by random signal-to-noise.

It's boring to meta-debate the quality of discussion / people's voting on a story or comment, so I won't pursue it much more here. But if something doesn't have a known practical value then let's talk about what its value is, or could be. Don't just vote someone down because you're offended that your pursuit / hobby was questioned.

This feels like its a "street car mods", "CPU overclocking", or even "distance running" kind of hobby. Part ego, part technical, part seeing how far you can push something. Sometimes these things have use (to you, or others), sometimes not.

There are two interesting parts to this. First, the stratospheric ducting, which is quite rare, but can have dramatic propagation for 6 meters (50Mhz) and above.

The second is the use of FT8, a new digital mode invented by Joe Taylor, W1JT, a nobel laureate. See https://en.wikipedia.org/wiki/Joseph_Hooton_Taylor_Jr. Of particular interest is how his research confirmed Einstein's theory about gravitaitional radiation From the web site,

On VHF bands and higher, QSOs are possible (by EME and other propagation types) at signal levels 10 to 15 dB below those required for CW.

The mode and other related modes are described here: https://physics.princeton.edu/pulsar/K1JT/wsjtx.html.

(Side note--Joe spoke at the Dayton Hamvention Contest Dinner a few years back, and brought some recordings of pulsars.)

Does the FCC reserve four digit call signs only for broadcast companies and nobel laureates or something? How does that work?

The amateur radio service has its own designated format for call signs: one or two letters, a single digit, then one to three letters. These days, the FCC normally issues a new licensee a "two by three" call sign (two-letter prefix, three-letter suffix), but depending on your license class, you can qualify for a shorter one. The Advanced and Amateur Extra license classes are allowed to have 1x2 or 2x1 call signs. According to the ARRL[1], there are currently 38093 Advanced licensees and 150793 Extra licensees (Advanced is no longer issued, but there are still quite a few Advanced who never upgraded to Extra).

Of course, a call sign can only be held by one licensee at a time, and most (or all) of the 1x2 and 2x1 are assigned (I'm not sure on the current state of things with 1x3 and 2x2). So one only becomes available when the previous holder loses it (by license expiration or death). There are far more Advanced/Extra licensees than short call signs.

There are also 1x1 call signs, but they are only issued on a temporary basis to special event stations (e.g., I have operated W8C, with a club whose normal call sign is W8YY).

1: http://www.arrl.org/fcc-license-counts

Obviously, getting a randomly assigned call sign that happens to match your initials would be pretty rare. However, the FCC allows licensed holders who hold a General or above, to apply for a "vanity license" whereby a request is made for an unassigned or abandoned call sign on a first come, first serve basis. Abandoned call signs are those where the owner has either died or has not renewed their license for a period of 3 years following the expiration of the license. This is how I picked up my current call sign and I'm pretty sure that Joe Taylor got his this way.

To add to this how non-US licenses are done, there is an additional rule with a number prefix, For example a station in Kuwait might have a call beginning with 9K2.

Additionally, some have two digits, for example a Slovenia call might be S52.

So the above rule would be modified to be zero or one digit, one or two letters, and one or two numbers, followed by suffix.

--w8lvn, ex-YJ0VN. --

In related non-news, it is possible to bounce signal off a meteor trail in the atmosphere. How cool is that?


And you can bounce signals off airplanes too, which I would love to do someday.

Some more context: this was done on FT8 which is a digital mode designed to shine in weak signal work such as this. FT8 can decode signals as low as about -24DB. On HF, FT8 is used to go around the world. Even QRP (10W or less) a lot can be done. It's JUST for making a contact, there's no conversation to be had.

The whole QSO took just a couple of minutes. It only needed to re-transmit one frame. Each frame takes 15 seconds.

What's great is that since the QSO (conversation) is so fast, the conditions can be really variable and you can still make the contact. I'm not surprised it was first done with FT8.

73 de W7RLF

My longest QSO on FT8 is a touch over 5100 miles on 5w. That was pretty fun, especially since my little Bitx40 is feeding a Z dipole in the attic of my single story house. Definitely not optimal.

A fellow bitx40 owner! Great to meet you. I love mine. I've hacked it to the Moon and back! They are great little radios. To bad the ubitx is such a turd.

What don't you like about the ubitx?

There are a number of things. The first is the feature creep. It is designed to do CW, but it does it quite poorly. The first 2-3 characters are dropped when you send. Secondly, the new version has a fancy screen that at least upon release, was tremendously slow. Lastly, it took them several versions to get it harmonics down to levels that were legal in the US. Before that, tons of modifications were required. The design is solid, but the PCB layout is poor.

The other thing is the PA. The layout is very poor. The higher the frequency, the lower the output. It's great at 30 meters and below, but 20 meters and up suffers. The BITX40 suffers from this too, but it's a single band radio and at 40m it works fine. I replaced the IRF510 with an RD15HVF1 and it worked great on 20M too. Mind you, this isn't an issue with the IRF510- it's an issue with board layout. The QRP Labs 10W PA uses two IRF510's in push/pull and can even work on 10m at full output.

TL;DR: Over complicated, poor PCB layout, feature creep.

That's not to say that Farhan isn't a nice fellow and a great ham- he definitely is! They just let this one out too soon before all the bugs were worked out, and allowed compromises that shouldn't have made it into production.

Wow, thanks for this. I hope they can get that fixed in the next version.

Honestly, the version they have is about as refined as they are going to get with it. There have been software changes that make the display better, and it's hackable so that you can make your own VFO for it etc, but the design has some fundamental flaws. To put it in perspective, v5 and v6 are almost identical except for the display. All of the same CW, layout, output, etc problems exist on the v6 as they did on the v5.

Keep an eye out for the QRP Labx QSX. It's been in development for a long time but will probably blow everything else out of the water, even things costing 10-15x as much.

FT8 is part of a suite of digital transmission modes that are designed for weak signal / long distance communication. Often times these modes can be decoded even when the signal is below the noise floor.

More details here: https://en.wikipedia.org/wiki/WSJT_(amateur_radio_software)#...

That's super impressive even at 100W power at that frequency. Didn't even think that could be done at all. That antenna doesn't look like anything really special either, just an ordinary Yagi as far as I can see. Single reflector.

To be fair, doing it from two islands way in the Atlantic is a bit of a stretch ;)

Only a little bit. This is quite incredible. I can imagine that doing it near population centers would be almost impossible.

Of course; it’s a remarkable feat either way.

If that population center happens to be Iceland, just walk over to the Mid-Atlantic Ridge and hold a radio on each side. That is equally valid for "trans-Atlantic".

The first transatlantic flight (Alcock and Brown) went from an island to an island. Lindbergh's famous New York to Paris flight left not from New York City (which is mostly on islands) but from Long Island.

Yes, but these islands are a lot further from the land on either side of the ocean. When you look at the map it looks less impressive than Alcock and Brown.

But in fact this 432 MHz contact is over a greater distance, 3867 km, than Alcock and Brown's flight of 3040 km (https://en.wikipedia.org/wiki/Transatlantic_flight_of_Alcock...)

So calling it trans-Atlantic actually undersells it in comparison with other well known trans-Atlantic feats while at the same time setting people up to think the opposite.

Is there some technical innovation here enabling this, or had nobody ever tried it before?

What are possible applications?

I think those are very good questions. Technically, they seem to use pretty ordinary gear. The bit rate is super low, about 5 bps so you're not going to be sending over your movies any time soon. It's been tried but nobody ever succeeded and conditions would have be just so for this to work.

Possible applications from a practical point of view not that I can see, though I'm sure that now that it has been shown to be possible there will be attempts to replicate it and from harder locations.

But HAMs are known for doing things the hard way, after all, you could just pick up the phone and talk, that's not what this is about. It's about being able to do it, just like mountain climbing.

UHF is line-of-sight. The article speculates about a transient effect ("marine ducting") that allowed the signal to propagate further this time. It's not likely to be reliably repeatable.

FT8 is ~10 bits/second (think of it as CW/morse code + better modulation + forward error correction).

> Is there some technical innovation here enabling this

I guess you could say the SDR based ICOM IC-9700 [1] transceiver FG8OJ used is enabling this by being reasonably priced [2] and off-the-shelf. It was released in January 2019 and has made experimentation of VHF/UHF more accessible.

[1] https://www.icomamerica.com/en/products/amateur/hf/9700/defa...

[2] https://www.hamradio.com/detail.cfm?pid=H0-016656

- Weather happened to be favorable for a brief window of time

- The FT-8 mode makes barely-possible communication possible

Although this is a wonderful accomplishment, it should be noted that tropospheric ducting happens every summer between the west coast of the US and Hawaii (at approximately the same distance of ~3800 km). The highest frequency contact was on 5760 MHz. Even I've made contact with Hawaii through the duct on 144 MHz from Silicon Valley (behind the Santa Cruz mountains). Signals are so strong, normal SSB voice can be used.

Is there a COTS radio set I could use for non-line of sight communication in the mountains?

https://elecraft.com/products/kx2-ssb-cw-data-80-10-m-transc... is the de-facto backpacking HF rig, usually the inreach[1] and similar are good enough for most people and doesn't require a license (just subscription).

[1] https://explore.garmin.com/en-US/inreach/

Amateur radio equipment in the so-called HF band can get you non-line-of-sight transmission. You'll need a really big antenna, and you'll need to be content sharing a few hundred kHz of spectrum with everyone else on the same continent.

"Big" doesn't necessarily mean "heavy" or "bulky" though. A decent length of lightweight wire and a tree can get you a very long way.

You can have a lot of contacts with a pretty minimal wire antenna, such as a dipole.

In the US, if you have a General class ham radio license, you could do it on the 7Mhz frequency if your antenna is relatively close (less than 1/4 wavelength) to the ground. See https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&c...

At higher frequencies (such as the 432 MHz used in this trans-Atlantic contact), the radio waves will not be reflected by the ionosphere and will disperse.

I think Inmarsat makes a nice little unit ;)

This is inspiring. I’ve heard about things like FT8 and WSPR and have taken the first steps to get on track for a 10W license. Is it feasible to put together a simple transceiver to send short messages over 200km? I’d love to have an out of band way of staying in touch with my family that doesn’t rely on any one else’s infrastructure. The closest thing I’ve found are either RTL SDR hacks (receive only?) or the Elecraft kit ($900 for something way more Gucci than I think I deserve, given my amateur noob status!). For some reason I’m having trouble answering this question for myself, using internet searching!

I did US to Australia with a Raspberry Pi as the transmitter, a QRP labs filter for 10 Meters to clean up the signal, into an MFJ Tuner and then a random wire over the house and no other amplifiers. Like 100mw or less? WsprryPi essentially just turns the pin on an off really quickly to generate the signal. This was with an Amateur Extra license.

To be clear here, there is no such thing as an "10W" license. The FCC grants three types of licenses, each with increasing privileges. Any licensed person can operate at power levels up to 1500 watts for General and above, 200 watts for Novice/Technician. Operating at 10 Watts and below is a popular form of communicating called QRP. It does, however, still require a license. You also need to have a licensed individual at the far end if you want to have two-way communications. If they're receive-only, then no license is required.

OfCom licenses sound similar, but with the bottom rung license (“Foundation License”) requiring low power operation (max 1W to 10W) while you learn the ropes.

Page 9 of IR2028 if you’re interested:


Is this tied to the lack of airplane flights?

I see other comments that bring up the 'RF pollution' from aircraft travel..all of those airplanes spewing RF, and harmonics all over. How about normal pollution? All those tons of burned hydro carbon absent from the atmosphere (10K to 40K feet). Is it possible the non-normal chemical composition of the air is impacting the observed ducting? (de WB0VIX/5)

Interesting observation. Lots of radio traffic by aircraft might substantially raise the noise floor, even though they do not operate near that particular frequency one or more of their harmonics might interfere with signals that quiet. 432 is suspiciously close to 4 times 108 so you may be on to something there.


For local communication, e.g., state to state, a common mode of attempts involve bouncing signals off of airplanes. But transatlantic using this method would be quite unlikely.


I would not be so categorical about that. 108 MHz is the low end of the VHF airband and 432 just so happens to be 4 times 108. So it may very well be that this connection would under normal circumstances be impossible due to interference.

What is the context here?

Very long distance radio link with relatively modest power at a super high frequency. Normally you'd not get much better than line-of-sight with a setup like that. So you have to work DX using satellite or EME.

It helps that FT8 is amazing. I can easily contact Japan from Massachusetts using a modest "cobweb" antenna (on my side) and a large beam antenna (Japan side). 100 W, but this is on shortwave which can bounce off the ionosphere.

WSJT-X is the software by Joe Taylor, who is a Nobel Laureate. The signal processing part of the program is written in Fortran.

Yea, ft8 is pretty cool. I've been able to work Europe on 6m during the summer E season (and hear Japan) along with some amazing dx contacts under marginal conditions on HF with it just using a simple dipole antenna.

That last sentence means that if you want to contact distant stations, you have to connect through satellite relays or by bouncing radio signals from Earth to the Moon and back to Earth (EME)

It's an ultra high frequency. Super high frequencies are from 3 GHz to 30 GHz.

Does this mean I can open my garage door over the Atlantic?

100W. Holy cow.

At a wavelength of 70 centimeters (432 MHz). All via the magic of extremely effective error correcting codes (and fairly rare atmospheric conditions).

Related, I'm amazed that my little $70 WSPR transmitter can push a 20m/14MHz signal from San Francisco to Georgia using only 0.2W, transmitting on a pretty lousy backyard dipole only 10 feet off the ground. True, it's only a beacon ("call sign Kxxxxx transmitting from SF at 200mW"), but still...

WSPR being another Joe Taylor invention https://en.wikipedia.org/wiki/WSPR_(amateur_radio_software)

I got from the USA (east coast) to Tasmania on less than 10 watts once, but not on 70cm.

I got from central Switzerland to Japan on about 10W on 20m once using JT65 or JT9 (I can't remember which). The antenna was a random length of wire tied a rock and tossed out of my fourth-story apartment window into a field below.

I've done US east coast to Australia and New Zealand on 160m, with 5 watts and a vertical. Well, the vertical was 90' of tower and had 40,000 feet of wire underneath it and was feed with 1 5/8" hardline, but still.

BTW, wasn't my station, but a friends I help with.



GPS satellites broadcasting L1 signals are transmitting 25 bit/s at 25.6W and they're only about 12551 miles away and moving at 8700 mph.

But they are line of sight. That's what makes this so special.

Stars are many lightyears away, and radiate insane amounts of power the vast majority of which is lost. By the time it reaches here you may need a very long exposure to be able to see them at all. But it is line of sight. These waves were of the line-of-sight variety and somehow they were bent around the planet enough to register. That's a very hard to achieve thing.

Voyager 1 is still in contact using a nominal 23W, despite being over 13 billion miles away and heading further out at over 10 miles per second.

Since it launched in 1979, have software updates improved the error correcting codes in Voyager's radio communications?

That was done in 1989 with an update to Reed Solomon Viterbi – Version 2.


I have lightbulbs that can do 200W!

I was under the impression that we can propagate across the entire globe such healing vibrations.

... but prop trading firms have been doing this for a long time.

"Shortwave radio" occupies the HF band, which has very different behavior from the UHF band discussed in this article. Amateur and commercial broadcasters have been using HF for transatlantic communications singe long before high-frequency trading existed.

Maybe this would have been a better response to the grandparent comment than downvoting it, as I don't think it's reasonable to expect most HN commenters to know the difference between UHF and HF (or even that they're different things), and the article makes no mention of it.

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