QRSS - Very Slow CW

QRSS is a derivative of the CW Q-Signal QRS for "Please lower your code speed". By using extremely slow CW, it is possible to use a computer sound card and special software to extract CW characters from below the audible noise floor. Morse code element lengths of 10 to 30 seconds (or even longer) per dot are commonly used.

Amateur VLF operators have used QRSS techniques to span the Atlantic at 136 KHz and to receive very weak VLF beacon transmissions from distant locations. By adopting these same techniques, QRP operators can push the envelope of very low power HF communications.

On the receive end, the audio output from the station receiver is fed into a computer sound card. When processed by special QRSS software, the magic happens and signals in the receive "window" are displayed. QRSS morse code character elements are visible as horizontal traces in the slowly scrolling display. In effect, the computer becomes a very narrow bandwidth filter by which coherent CW signals are extracted from the non-coherent receiver noise.

In the photo above, the characters "Ų" and "C" of callsign WŲCH are visible. This Spectran screen shot was taken by AA4XX on March 2, 2002. The mode was QRSS30 (30 second dots) and the WŲCH 30 meter transmit power was 1 milliwatt for this test.

Addtional screen shots from AA4XX's beacon tests on October 4, 2003 are here: 100403

There are at least three software programs written for QRSS reception. They are available for download at the following sites:

To transmit, an amateur transmitter is keyed by a computer program to generate a very slow morse transmission. A very stable transmitter is desired for QRSS mode because of the very narrow bandwidths used. Also, a means of determining the exact transmit frequency, down to the Hz, is desirable.

The QRS program is commonly used to transmit QRSS. Version 3.17 for Windows 3.1, 95 98 and ME is available for download at the following site:

QRS Version 4.08 is now on line and is for Windows 98, ME, NT 4, 2000 and XP. Changes available with QRS 4.08 are:

1. Message size increased for 70 chararcters to 250 characters
2. Soundcard can be used for DFCW tones and CW sidetone
3. AutoStart feature allows automatic and unattended beacon mode

A simple keying interface will be needed to convert the serial port output to key closures. Information on construction of a simple one transistor keying interface is provided with the QRS software package.

Beacon test transmissions typically are announced via E-Mail with the time, frequency and power level known. The transmitting station will start at the announced time with his callsign and then a 4 or 5 letter code word. The receiving stations will attempt to copy the code word which is then relayed back to the sending station via E-Mail reception report. The successful reception of the code word confirms the beacon reception.

The next screen shot below was taken by Randy, K7TQ in Moscow, Idaho of a multiple station 30 meter beacon test on March 4, 2002. In this test, stations ON5EX, AA4XX and WŲCH were on the air simultaneously with 200 milliwatt beacons. Randy captured AA4XX (top trace) and WŲCH (lower trace) in the same Argo screen shot. These two stations were separated by less than 30 Hz in frequency.

The next two screen shots were taken during a 2-way QRSS QSO on March 10, 2002 between Paul Stroud, AA4XX and WŲCH on 30 meters. Both pictures were taken at WŲCH which show AA4XX's signal.


Paul, AA4XX is sending a "M" signal report to WŲCH for a 50 uW transmission. AA4XX is transmitting at 100 uW.	AA4XX is sending "GL" at the conclusion of the QSO. Paul's transmission was at 50 uW power output.

This QSO took 5 hours to complete, with each station taking turns transmitting for one hour (by the clock). The mode was QRSS 60 (60 second dots). The distance between WŲCH and AA4XX is 892 miles which results in a 50 uW QSO at 17,840,000 miles per watt.

QRSS signal reports use the "T - M - O" format instead of RST, similar to weak signal EME communication reporting.

How Low Can We Go?

The series of 30 meter beacon tests between AA4XX and WŲCH demonstrated that information can be exchanged at transmit power levels as low as 10 uW. Tests at levels as low as 900 nW (nanowatts) were attempted with some signal detection but no information was exchanged at that level.