
First 2200-Meter Transatlantic Contact by US Radio Amateur Reported (2018) - segfaultbuserr
http://www.arrl.org/news/apparent-first-2200-meter-transatlantic-contact-by-us-radio-amateur-reported
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audiometry
huh? Am I mis-reading/understanding the units? 80m bands are common, and I
guess I've heard people talk about 160m. This is 2200m? 2.2km? What would the
antenna look like? a quarter-wave dipole? haha Is this the kind of thing subs
would use to communicate, for example?

~~~
segfaultbuserr
> _This is 2200m? 2.2km?_

Yes, it's 136 kHz.

The NIST transmits the 70 kW WWVB time signal at 60 kHz (5000-meter) in order
to inform you the standard time in UTC from atomic clocks. It was extremely
useful before GPS, less useful today, but it still serves a hundred thousands
of radio clocks, NTP time servers or so.

In the beginning of radio, even lower frequencies were used. The Grimeton
Radio Station (callsign SAQ) in Sweden uses 17.2 kHz, or 17441-meter. The
oscillator of the radio is not an electronic oscillator like a crystal, but an
extremely fast AC generator with moving parts rotating at one million RPM,
invented before vacuum tubes and subsequent establishment of "electronic
engineering".

This radio station still operates today for celebrations, and it can be heard
by amateur radio operators worldwide with their homemade equipment (a computer
soundcard can be the radio receiver, 17.2 kHz is audio frequency).

* [https://en.wikipedia.org/wiki/Grimeton_Radio_Station](https://en.wikipedia.org/wiki/Grimeton_Radio_Station)

> _haha Is this the kind of thing subs would use to communicate, for example?_

You greatly underestimated subs ;-)

136 kHz is Low Frequency. Submarines use Very Low Frequency (something like
SAQ's frequency), or Extremely Low Frequency, as low as 100 Hz, not a typo,
it's _hertz_.

> _What would the antenna look like?_

Every wire is an antenna, you don't really need a "real" antenna to get the
radiation out or pick up the signal. At low frequencies, the antenna is
_always_ inefficient, and one just needs to accept this fact and gets used to
it.

Usually the antenna is built to be as large as practical, but not larger. If
you are the military, you can build a multi-kilometer antenna, but if you are
an amateur, it would be as large as your rooftop or backyard can fit, not
larger, then you build an impedance matching network to make it usable (but it
doesn't improve the efficiency of the antenna itself), and you put as much
power as possible into the antenna.

Finally, receiving a large station is easy, when they transmit tens of
thousands of watts, a small and inefficient random-wire antenna can pick up
the signal from, e.g. WWVB or SAQ. It's how nuclear submarines receive one-way
communication from the command & control.

Receiving a 1-watt amateur signal (legal limit for 2200 meters) is much more
difficult.

The article says,

> home-built single FET 200 W class E amplifier, a 90-foot top-loaded vertical
> antenna, this gives me no more than 0.5 W EIRP, probably less.

200-watt in, 0.5-watt EIRP out, the antenna efficiency is 0.25%.

And it's a transatlantic communication from U.S. to Great Britain without
gigantic military antenna and about 0.5-watt of radiated power, I think you
can now understand the technical achievement here.

