Common HF Signals, a few examples

A Wobbler - possibly an unstable PA

The frequency swings up and down rhythmically.

I wonder if this is caused by the antenna swaying in the wind, changing capacity to ground.

Another Wobbler plus drifting carriers - Russian Freeband

VARAC

Digital ragchewing mode with robust, adaptive modem.

WSPR - Weak Signal Propagation Reporter

A one-way transmission acting as a beacon, able to be received at extremely low signal levels

FSK / RTTY - Hamburg Weather

RTTY uses 2-frequency FSK

CODAR - Coastal Ocean Dynamics Applications Radar

CODAR was initially designed to monitor oceanic conditions such as wave height, Tsunami surge, wave direction etc. It is now also used to monitor marine traffic movements.

CODAR - Coastal Ocean Dynamics Applications Radar

Coarse trace.

Qadir / Ghadir - various

These Iranian over-the-horizon radar systems are often to be heard between 28600 and 29700 kHz with a characteristic long 2-tone sound.

JORN - Jindalee operational radar network - Australia

Characterised by its changing sweep rate.

OTHR - Pluto II - Akrotiri

A distinctive 12.5Hz, 25Hz or 50Hz big, bold, wide over the horizon radar system.

Ionosondes - MUF Hunters

Sweeping across the HF spectrum, these familiar signals allow the Maximum Usable Frequency to be determined.

Digisondes - Digital MUF Hunters

Sweeping across the HF spectrum, these familiar signals allow the Maximum Usable Frequency to be determined.

Digisonde - better audio recording

You've almost certainly heard this sound intruding on your listening at some time. This is the culprit - the digisonde.

SuperDARN - Auroral radar

SuperDARN radars number around 40 globally and are primarily used to map high-latitude plasma convection in the F region of the ionosphere, but the radars are also used to study a wider range of geospace phenomena.

STANAG-4285

One of the most common NATO data signals on HF, they have a busy, mechanical sound to them.

Most are encoded.

Russian Letter Markers

Placeholders to keep various frequencies occupied, so that they will be available when needed.

The Buzzer - Russian placeholder

Placeholder to keep frequency occupied, so that it will be available when needed.

The Alarm - Russian placeholder

Placeholder to keep frequency occupied, so that it will be available when needed.

The Goose - Russian placeholder

Placeholder to keep frequency occupied, so that it will be available when needed.

TAH - Civilian Turkish weather fax placeholder

Placeholder to keep frequency occupied, so that it will be available when needed.

Weather-Fax

For ships who have no internet or satellite connection (tricky to point an antenna during rough seas), the HF WeatherFax service is ideal.

SSTV

Sending colour pictures to each other seems so simple these days, but try it without a data network :-)

SSTV is slow scan television, using voice bandwidth to send low resolution colour images over HF or VHF