G'day James,
I am intrigued by your posting:-
I think Rik's idea of displaying 2 tones differentially ought to work, but
it would place quite stringent demands on frequency stability.
This certainly does work as I have been using such a system for several
years now. I called it FDK for Frequency Difference Keying. I have had
trouble explaining what is really a very simple protocol over those several
years and in frustration changed the name to Wanjina to avoid association
with VFSKCW, DFCW, FSK, etc.
However, FDK wasn't the first 'stab'. It all started for me almost three
years ago when I was toying with the idea of speeding up the slow QRSS
technique by encoding dots and dashes as two slightly offset tones of the
same duration. I had a soundcard program written to do that and convinced
myself that it would work. However, at that time very few people were set
up to send soundcard derived signals, so I shelved the code until Rik made
the protocol popular (only after much persistence by Rik against much
opposition if I recall correctly). I quickly
resurrected the code and this is the basis of the VFSKCW (Visual Frequency
Shift Keying C W) program which was used recently to cross the Pacific on
137.790kHz (ZL2CA / W4DEX).
Next came what I called AFK (Absolute Frequency Keying). Here each
character is encoded by being assigned its own frequency (say 1000 - 'A',
1010 = 'B', and so on). The duration of each tone was arbitrarily chosen
to be 60 seconds. Subsequently, I found that this is actually a very old
technique first invented by an Englishman circa 1958 and is called Piccolo
Mark 1. Lately this method has been subsequently re-invented as PU-43 and
PGP-1. Once again I had shelved this method as the absolute frequency
accuracy was beyond what was in use at the time, although I did experiment
with it in Laser DX and Infrasonics where absolute frequencies translate
into reasonable ppm requirements.
After this I began to see that more and more operators were getting into
soundcard software transmitting so I attempted to push another scheme which
I called FDK (Frequency Difference Keying) to relieve some of the stringent
frequency stability requirements. Here the characters are not encoded in
an absolute frequency, but the difference between two tones ('A' = 5Hz
diff., 'B' = 5.1Hz diff., and so on) of 60 seconds duration. For several
years I have been trying to push this protocol as it removes the problem of
long term drift and the need to 'net' accurately. Problem was that I
couldn't seem to explain the protocol, probably because it was too simple
and people were expecting something exotic and mysterious.
To try and disassociate FDK from VFSKCW, DFCW, FSK, etc, I changed the
protocol name to Wanjina. A HF version of Wanjina was developed (called
WaHiFer) and transmissions using 2mW EIRP were received and decoded by Lyle
K0LR on 13.555450MHz (a distance of more that 16000km). Argo was used to
capture data and that data was analysed off-air to decode the signals. The
path from in VK2 to the US is unstable at HF and there was considerable
smearing of the signals - however the Wanjina WaHiFer S/W coped with that by
decimating in time and using a mode detector.
At LF this smearing is not significant and a different Wanjina LF S/W would
be more suitable. If it can work at HF then it can work at LF. Perhaps
by next season I will have the time to write it (WaLowFer ?).
I know some of you have heard this before and I apologise for this, but as
it seems as if FDK/Wanjina is being re-invented:
I think Rik's idea of displaying 2 tones differentially ought to work,
at the risk of annoying everyone, I thought it useful to re-iterate and try
and explain again as well as state that based on my actual field results it
actually does work.
BTW, because I have only recently re-subscribed I missed Rik's post.
Could someone forward it to me please ?
73s Steve Olney (VK2ZTO/AXSO - QF56IK : Lat -33 34 07, Long +150 44 40)
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