
First trans-Atlantic contact made on 432 MHz - lightlyused
https://ei7gl.blogspot.com/2020/04/first-trans-atlantic-contact-made-on.html
======
teraflop
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.

~~~
xelxebar
> ... 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?

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

~~~
devxpy
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?

~~~
vvanders
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.

------
wglb
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](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](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.)

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

~~~
kd0amg
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](http://www.arrl.org/fcc-license-
counts)

~~~
sizzzzlerz
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.

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

[http://www.ccas.ws/radioastronomy.html](http://www.ccas.ws/radioastronomy.html)

~~~
progre
Also cool: Moon bounce
[https://en.m.wikipedia.org/wiki/Earth%E2%80%93Moon%E2%80%93E...](https://en.m.wikipedia.org/wiki/Earth%E2%80%93Moon%E2%80%93Earth_communication)

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

------
geocrasher
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

~~~
taborj
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.

~~~
geocrasher
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.

~~~
lightlyused
What don't you like about the ubitx?

~~~
geocrasher
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.

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

~~~
geocrasher
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.

------
ohazi
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)#...](https://en.wikipedia.org/wiki/WSJT_\(amateur_radio_software\)#FT8)

------
jacquesm
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.

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

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

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

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

What are possible applications?

~~~
jacquesm
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.

------
drmpeg
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.

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

~~~
teraflop
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.

~~~
JshWright
"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.

------
gorgoiler
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!

~~~
sizzzzlerz
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.

~~~
gorgoiler
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:

[https://www.ofcom.org.uk/__data/assets/pdf_file/0028/53965/i...](https://www.ofcom.org.uk/__data/assets/pdf_file/0028/53965/ir2028.pdf)

------
aaron695
Is this tied to the lack of airplane flights?

~~~
jacobmarble
No.

~~~
jacquesm
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.

------
rjurney
What is the context here?

~~~
jacquesm
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.

~~~
jhallenworld
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.

~~~
lightlyused
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.

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

------
klodolph
100W. Holy cow.

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

~~~
lightlyused
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.

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

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

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

~~~
logicchains
A source to back this up: [https://spectrum.ieee.org/tech-
talk/telecom/wireless/wall-st...](https://spectrum.ieee.org/tech-
talk/telecom/wireless/wall-street-tries-shortwave-radio-to-make-highfrequency-
trades-across-the-atlantic)

~~~
teraflop
"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.

~~~
logicchains
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.

