G'day Rik,
I believe that the FDK/Wanjina system is an excellent tool for
propagation
tests, where the only goal is to have an identication of a signal.
The main disadvantage I see is the need of a linear TX, but maybe this
could be solved by transmitting the 2 tones sequential. If the tones are
send sequential they get the double of the power but only during half the
time, so SNR will be the same.
Actually you don't need a linear amplifier to generate two tones, Wolf has
been transmitted in the US LowFer bands using just an XOR gate.
Wanjina/FDK can be generated the same way. Of course, for the European
band this would not be suitable.
But my primary interest goes to a mode that will allow us to have a proper
2-way QSO within a timeframe of 60-90 minutes.
Assuming that we set the same requirements to have a valid 2-way QSO as
for
meteor-scatter or EME than we would need :
1. exchange of callsigns (official calls, no pseudo-calls)
2. exchange of some kind of report (T-M-O)
3. some kind of 'end of QSO' confirmation ('SK')
Yes. I agree. If we limit our experiments to Amateur rules then this is
true. However, many of us are almost purely experimentally-minded and are
excited by the information provided by, for example, the identification of
Bob Vernall's ZL6QH beacon. I don't know about you, but didn't know for
sure whether it could be done, but now we have a benchmark which will no
doubt spur others to invest in more power or bigger antennas to work towards
the formal QSO. For me the exchange of information in the most efficient
way is the bottom line - not whether it complies with some set of rules.
You are right when you state that FDK/Wanjina does not need absolute
frequency calibration, since each character already carries the reference.
If one would send the tones sequential it would mean that a reference tone
is sent, followed by a second tone with a shift unique for each character.
This is the advantage but at the same time the weakness of FDK, because it
means that you need about 40 different shifts what might become very
difficult to decode by eye and also requires a relative large bandwidth
compared to the proposed 7-tone system.
During the Wanjina tests on 22m (2mW EIRP decoded over 15,000km) in the
QRM-ridden ISM bands before I could write the decoding software, the Wanjina
signal was decoded by eye by the two people who became aware of the tests.
They simply used the cursor to mark the two lines and looked up a table I
gave them. As far as sequential tones, the IFK method I proposed way back
is a contraction of this (on my web-site), but both sequential systems
suffer from the either twice as slow (reference then data) or ambiguity
(IFK) between tones. But the point about the large bandwidth is a
weakness for sure.
Regarding SQUID : it sounds rather tempting and might an be interesting
step between simple one-way identication of a beacon and a full 2-way QSO.
I have about four or five different variants of SQUID in my head. I will
try and sort them out over the next couple of weeks and present them for
scrutiny. Basically they are different balances of bit-length and number
of tones. Also either one part for station ID and a trailing part for
operationalmode/signal report or a composite code (in micro-encoding terms -
like one byte for an opcode and then one byte for the operand, or the opcode
and operand combined in one byte).
But I feel that making a QSO really involves the exchange of regular
callsigns.
You are not alone in feeling this, but the question I honestly don't
understand is - why ?
BTW, the great thing about the ISM band (and at the moment the US LowFer and
the VK Scientific Licence) is that they are NOT Amateur bands so you don't
have a horde of hyperventilating hamsters hammering you for utilising a
couple of hertz of unoccupied spectrum space using some non-kosher
mode/protocol. Look what happened on 160m when narrowband tests were
attempted there. The ZLs don't seem to have this problem. They have
been engaging in experiments in their Amateur LF band for longer than most
without any angst. Very sensible and practical people the Kiwis are.
Like the Aussies were before we starting aping foreign influences and
started wearing our caps back to front. But I digress.
73s Steve Olney (VK2ZTO/AXSO - QF56IK : Lat -33 34 07, Long +150 44 40)
=============================================
HomePage URL: http://www.zeta.org.au/~ollaneg
Containing:-
ULF, ELF, VLF & LF Experimentation
MF 22m Experimentation
InfraSonic Experimentation
Laser Comms DX
=============================================
| 