Welcome to the gopherhole of the...
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[ 24th October 2026 ]
Since gopher could now be considered as existing on the fringes of
the Internet I have decided to dedicate these pages to my fringe
interests in electronics, computers and radio. By fringe-interests
I refer to subjects or projects which have solid foundations in
physics along with sound engineering principles but perhaps less
well known or publicised.
Why would I do this? Well, as a radio-ham it would be very easy to
write about regular ham-radio sunjects but any such text or
ramblings could just as easily be found on the wider Internet.
Therefore I propose to write a little about technical subjects on
the fringes of mainstream amateur-radio.
So, to kick-off I have chosen to write a little about QRSS as the
first fringe subject.
An Introduction to QRSS.
The following text does assume some background knowledge of amateur
(ham) radio and ham-radio terminology.
Before continuing, I should like to express my thanks to Andy
(G0FTD) for kindly allowing me to use extracts from his on-line
publication "74! The Knights QRSS Compendium".
(HTM) "74! The Knights QRSS Compendium" in pdf format.
So, what is QRSS?
QRSS is a niche facet of the amateur radio hobby requiring patience
and precision which is primarily focused on the study of radio
signal propagation. Its important to understand that QRSS is not
simply another digital communication mode for collecting grid
squares or call signs for DXCC.
In common with other narrow bandwidth data modes QRSS does involve
the use of a computer and FFT software for detecting and visually
decoding signals but the primary use of QRSS is for the study of
radio signal propagation. In this brief introduction to QRSS I have
intentionally avoided too much theory since background technical
material already exists on-line.
Some QRSS History.
QRSS has enjoyed increasing popularity over the past 25 years
though the techniques employed have existed for much longer. My
first encounter with QRSS came while experimenting in the-137 kHz
LF amateur band back in October 1999. Because of ERP limits and the
very poor efficiency of garden-sized antennas at 137-kHz a number
of OM's began experimenting with slow CW dubbed "SCW" using very
long dot/dash times. In SCW the dot timings are used to define the
speed of the various sending modes. So for example, SCW-3 would
indicate a 3-second dot duration while SCW-6 would indicate a
6-second dot duration. The corresponding dashes would then be
9-seconds for SCW-3 and 18-seconds for SCW-6 respectively.
Because of the very slow sending speeds only very narrow bandwidths
are required permitting a very high signal-to-noise ratio to be
achieved. By taking advantage of these narrow bandwidth SCW modes
it was possible to work much greater distances on the LF bands than
would be possible with conventional CW using the same ERP.
By ensuring the transmitter has a high level of frequency-stability
it becomes possible to detect the signal within a very narrow
bandwidth and at great distances even when the signal is weak and
inaudible on a conventional receiver. This weak-signal detection is
achieved by using FFT (Fast Fourier Transform) software and
displaying the results on a horizontally scrolling visual display
in near real time. Here are two examples of FFT software.
(HTM) ARGO written by I2PHD
(HTM) "FSKview" by Scott Harden (AJ4VD)
Decoding of these slow Morse signals is performed visually
(See fig-1) and for that reason it could be described as a
fuzzy-mode requiring both computer processing and human visual
processing.
(IMG) Fig-1 Example FFT software display.
(HTM) Fuzzy Modes!
By 2004 there was a small but rapidly growing group of dedicated
enthusiasts experimenting with QRSS in the HF amateur bands. Most
of this HF activity took place within a 100Hz portion of the 30 Mtr
amateur band around 10.140 MHz. At that time digital modes such as
WSPR and FT8 were still years away. Because of the difficulty of
visually decoding SCW (Slow-CW) in the presence of QSB on-off
keying of the carrier was quickly superseded by frequency shift
keying methods including FSK-CW (Frequency Shift Keying CW) and
DF-CW (Dual Frequency CW) while still retaining the timings of the
older SCW modes such as QRSS3 and QRSS6.
Typical FSK frequency shifts are about 4Hz with about 1Hz as a
guard band between adjacent signals. So in a 100Hz portion of
spectrum you can easily fit 20 separate QRSS signals. But there are
no issues if the QRSS experimenter decides to use a wider bandwidth
for their signals. Indeed, there are many examples of slow
Hellschreiber which occupy much more than 4Hz! See fig-2 for
examples of slow-hell and FSK-CW. Its not uncommon for two signals
to appear on the same frequency which we QRSS enthusiasts call a
"collision". But there are no penalties for occasional collisions.
Frequency coordination takes place via an on-line forum.
(IMG) Fig-2 Example of slow-hell and FSK-CW
(HTM) The Official QRSS Knights Forum.
With the increasing levels of QRM which exist on the amateur bands
today it's worth pointing out that local QRM does not effect QRSS
sending. It is still possible to monitor a signal being transmitted
from a heavy QRM transmitting location using one of the many
on-line SDR receivers which are often sited in low QRM locations.
So, for anyone wishing to do antenna testing or a propagation study
then local QRM would not be an issue. Also, because of the very
narrow bandwidth required for QRSS modes its often still possible
to copy signals with some level of QRM present. One very nice
feature of the FFT software is that only signals which are highly
coherent will be processed and displayed. QRM signals are often
very non-coherent and therefore largely ignored by the software.
While no mode is totally immune to man made noise QRSS modes do
perform exceedingly well in the presence of QRM.
Some terminology unique to QRSS.
Lets start by recounting the origins of the term "QRSS" which is
currently used to indicate sending signals slowly or very slowly.
The term is derived from the Q-code and is an unofficial extension
of "QRS" which means "send more slowly" or "shall I send more
slowly". By adding the extra "S" on the end of QRS we get QRSS
which has become an accepted term to describe the numerous slow
sending methods presently in use.
Other terms which frequently crop-up which are unique to QRSS
operation include "MEPT" and "QRSS-Knight". "MEPT" is an acronym
for Manned Experimental Propagation Transmitter. The term emerged
about 20 years ago in response to concern by some experimenters
regarding the legality of QRSS operation. It was decided a clear
distinction between QRSS operation and unattended beacon operation
was required. The outcome was the creation of the term "MEPT" which
is used to describe a QRSS transmitter used for the study of radio
signal propagation. The "Manned" part of the acronym was intended
to make it clear that QRSS enthusiasts were not leaving
transmitters operating unattended!
Fortunately, regulatory changes to the amateur radio licence in
many countries in recent years have resulted in less ambiguity
regarding QRSS operation. The use of propagation beacons limited to
5 Watts ERP or less is now permitted (with certain conditions)
within the terms of the UK amateur licence. For those living
outside the UK it would be wise to check the amateur licence
conditions within their own country along with any geographic
restrictions that may also apply.
The origins of the term "QRSS-Knight" are a little more obscure.
As I recall, the term QRSS-Knight was first adopted around 2005
and is simply a reference used to describe a QRSS enthusiast.
I confess I have no idea where the term came from or why it was
adopted but "QRSS-Knight" rapidly gained traction and remains in
use to the present day.
QRSS Transmitters.
In its most simple form a QRSS transmitter or MEPT is a very low
power QRP signal source. In the world of QRSS anything over 500 mW
is considered QRO! Power levels in use typically range from 1mW ERP
to a few hundred mW ERP so its fair to say QRSS-Knights are
generally milliWatters. In order to make the signal easily
identifiable the carrier is keyed on-and-off (SCW) and/or
periodically frequency shifted (FSK) plus or minus a few Hz. QRSS
signals often include a periodic audible CW message at perhaps
12-WPM which may include operator call-sign and location
information.
QRSS signals sometimes use a combination of frequency shifting and
on-off keying in order to create simple but unique visual patterns.
This often helps to quickly identify an individual operators MEPT.
A sort of visual signature. See figures 3, 4 and 5 for three more
examples QRSS signals. In figure-3 the addition ghosts of the main
FSK-CW signal are caused by aircraft reflections.
(IMG) Fig-3 Example QRSS signal showing aircraft scattering.
(IMG) Fig-4 Example of two QRSS signals on different frequencies.
(IMG) Fig-5 Example QRSS pattern signal showing CW-ID.
A number of QRSS operators also provide on-line receivers or
"grabbers" for the benefit of other enthusiasts. These remote
grabbers monitor various QRSS sub-bands within the LF/HF/VHF
amateur frequency bands and periodically upload their screen
captures or "grabs" to the World-Wide-Web. This enables other QRSS
enthusiasts to remotely monitor their own transmissions in near
real-time.
(HTM) On-Line QRSS Grabbers.
How is QRSS useful?
Here are two examples of how QRSS could be useful in amateur radio.
Imagine you enjoy experimenting with home-brew antennas and would
like to get some idea of the far-field performance of your latest
creation. You may for example want to make comparisons of your new
antenna to an existing antenna. You could call CQ to make a few
contacts to obtain signal reports but you will never be certain
those reports are accurate! The stations contacted may have poorly
calibrated S-meters and/or a well-meaning OM may give you an overly
generous signal report.
More reliable test results could be obtained by employing a QRSS
transmitter in such a way as to transmit alternately on each
antenna for a fixed period of time. For example, a unique pattern
could indicate the new antenna under test with a different pattern
used to indicate the existing antenna. You could then view your
signals using one of the many on-line grabbers and identify which
antenna offers the best performance. A similar technique could also
be employed to compare the directional properties of two different
antennas. Because the power levels used for QRSS are normally very
low it means that prolonged on-air testing is much less likely to
result in upsetting other band users.
Alternatively, you may be interested in the study of grey-line
propagation? Figure-6 shows an example of a QRSS grey-line signal
capture in which one of the signal is displaying noise-like
characteristics possibly caused by Doppler effects. Some of the
on-line grabbers also offer the option to view earlier grabs so its
possible to see how propagation has been changing over time. These
are just two possible applications and readers may think of more
imaginative ways to use QRSS in their own experiments.
(IMG) Fig-6 Example of QRSS grel-line reception.
TX/RX equipment for QRSS.
In the early days of QRSS enthusiasts had to develop their own
equipment from scratch or adapt a piece of existing equipment. But
today QRSS kits are readily available for much of the HF/VHF
spectrum. But for those interested in pursuing the home-brew route
into QRSS the equipment can be very simple in design. A QRSS TX
might consist of a single transistor crystal oscillator feeding a
few mW to a low-pass-filter and an equally modest antenna. Indeed,
such a setup is a very good introduction to the world of QRSS.
Using very modest power (less than 10mW) you can get a feel for
QRSS without the risk of causing any undue QRM.
A single-band QRSS receiver can be equally simple in design using a
direct conversion receiver feeding into an existing shack PC or
laptop. The audio output from the receiver is fed into the
sound-card input of the shack computer running one of the many free
FFT software packages available. If you wish to explore the
home-brew route then my QRSS web-pages include a simple, high
performance direct-conversion receiver design for the 30 Mtr band.
There are also some simple crystal-oven designs for increased
frequency stability.
(HTM) Example of a simple DC receiver for QRSS reception.
(HTM) Simple Crystal Ovens for QRSS.
With both home-brew transmitters or a QRSS kit from QRP-Labs it has
become standard practice to include a micro-controller to generate
the QRSS-CW, FSK-CW, DFCW, Patterns, Slow-Hell, Fast-CW etc. In the
case of the QRP-Labs kits the array of sending options supported by
the software is very comprehensive. But if you choose the home-brew
software approach it need not be too challenging. Because the
signaling speeds are very s-l-o-w writing the software is very easy
and the hardware requirements are minimal.
My software skills are virtually non existent but solutions exist
even for software-challenged people like me. For my 2006
retro-styled, junk-box MEPT using three re-cycled PC-PSU enclosures
(see fig-7) I used my BASIC (no pun intended) software skill and a
micro-controller from the Picaxe range.
(IMG) Fig-7 Retro-styled home-brew QRSS-TX & SWR bridge.
(HTM) The PICAXE range of user friendly micro controllers.
Picaxe micro-controllers are very user friendly and if you have any
experience of old-school, retro computers such as Commodore-64, ZX-
Spectrum, ZX81 or BBC Model-B etc then you would have no trouble
writing TX software using a Picaxe micro-controller. Other possible
micro-controller options include Arduino or the Raspberry Pi Pico.
(HTM) The Arduino Single-Board Micro-controllers.
(HTM) The Raspberry-Pi Pico Micro-controller.
QRSS Kits and Hardware.
For those who may wish to avoid designing their own QRSS MEPT or
receiver then hardware exists in kit form and is readily available.
The first place to look for QRSS kit hardware is QRP-Labs run by
Hans Summers (G0UPL) who is also a veteran QRSS enthusiast.
The "Ultimate3S QRSS/WSPR kit" (fig-8) will operate on all amateur
bands from 2200m to 2m requiring only a low-pass-filter or filters
for the chosen bands of operation. The kits are easy to build with
excellent, easy to follow instructions. QRP-Labs also offer a
number of optional extras such as a compatible GPS receiver
(QRP-Labs QLG2) to achieve additional transmitter frequency
stability and timing accuracy for the WSPR mode.
(IMG) Fig-8 Ultimate3S QRSS/WSPR kit.
(HTM) QRP-Labs U3S QRSS Kit.
(HTM) QRP-Labs Receiver module.
(HTM) QRP-Labs QLG2 GPS Receiver.
If you are sufficiently curious to know more about QRSS then I
highly recommend reading the 2018 edition of "74! The Knights QRSS
Compendium" where you will find more about the history of QRSS.
The 74! Compendium editions describe current QRSS trends and
contain much more information than contained in this brief
introduction. Follow the link below for the QRSS compendium.
(HTM) "74! The Knights QRSS Compendium" in pdf format.
If you decide that QRSS is something you would like to try then I
also recommend joining the QRSS-Knights forum.
(HTM) The Official QRSS Knights Forum.
Finally, if you have any questions, comments or "heckles" please
feel free to contact me.
73
M0AYF aka Silentone
Contact: my-sdf-username @
sdf.org
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