VFSKCW - Soundcard Version of Rik Strobbe's DFCW (circa 2001)
Prompted by Rik Strobbe's posts to the RSGB LF Reflector, I had resurrected some code that I was experimenting with earlier (late 1998) which modified the standard QRSS mode by replacing the dots and dashes with two frequencies. As I already had the code written from those earlier experiments, it only took an afternoon to whip up a user interface modelled after Rik's QRSS program.
Used to Set a Number of LF DX Records:
Version 5 of this software was used to cross the Pacific on December
1, 2001 on the frequency of 137.790kHz. The participants were Bob ZL2CA
and Dexter W4DEX. The distance is about 13,600kms. I am pleased that
my VFSKCW transmitting software used by ZL2CA has been a small part
of this achievement. Here is the historical detail:-
1 December 2001: ZL to W4 on 136kHz
ZL6QH smashed the world 136kHz distance record when he transmitted the letter Q repeatedly in QRSS with a dot speed of 120 seconds. W4DEX in North Carolina received several Qs, using Argo software, at a distance of 13,633km. W1TAG received a fragment but not enough to confirm reception. The previous record for 136kHz was M0BMU to W4DEX set last winter at 6380km.
Operator Bob Vernall, ZL2CA, says: "all went well at ZL6QH from a transmission point of view, for all New Zealand hours of darkness. I had a brief outage for 10 minutes, from 0730 UTC, but that was before sunset last evening. I went QRT at 1600 UTC, an hour after local sunrise. ....... I also consider my TCXO master oscillator controlled LF frequencies held within 0.1 Hz of declared. I had a two-way QSO on 40 metres with Steve VE7SL, but he got nil on LF, so ZL6QH did not depart from the 120 second dot length all night."
VE7SL was previously the only North American station to receive a transpacific LF station (see below).
The picture is one of three posted by W4DEX. The dashes of the letter Q (with no space between them) are clearly visible at +0.1Hz of nominal, and the dots some 0.4Hz lower.
Several UK stations monitored but did not copy anything. ZL6QH will be having another all night transmission on 15 December.
Bob, ZL2CA summarised the event as follows:
CLAIM OF ZL TO W4 AMATEUR LF DX 4 December 2001
On Saturday 1 December
ZL6QH sited near Wellington, New Zealand transmitted a low speed frequency
shift keyed test signal in the 136 kHz band. This was the first time
that DX testing in he 136 kHz band has been tried by ZL6QH, since having
the 135.7 - 137.8 kHz band recently added to the club station Low Frequency
Permit. Various DX listeners had prior knowledge of the ZL6QH test transmission,
which ran for all hours of local darkness. Dexter W4DEX managed to receive
and positively identify signals from ZL6QH. The path length from ZL6QH
to W4DEX in North Carolina has been calculated as 13,633 km. W4DEX used
receiving equipment with the audio fed to a computer sound card for
filtering and display of the signal.
This is now a popular technique
used for "below the noise" detection of amateur LF signals, as ZL6QH
was using 120 second dot length (each transmitted bit was 2 minutes)
and there can be nil detected by ear, yet coding of the wanted signal
can be seen after DSP filtering and displaying on the screen. The screen
display can be captured and saved as a file, as a record of what was
received, and for passing to others by electronic means. Best reception
was reported as being between about 0904 and 0950 UTC, which is approximately
one to two hours after ZL6QH sunset at 0800 UTC and about two to three
hours before W4DEX sunrise at 1212 UTC. The radio equipment used by
W4DEX was a square loop antenna, 2.3 metres per side, balanced pre-amplifier
feeding an HP3586B selective level meter. The ZL6QH transmitted signal
used dual frequency keying, with 0.4 Hz frequency shift. The uniquely
coded transmission consisted of repetitive sending of QQQQQ. sent as
137.7900, 137.7900, 137.7896, 137.7900 and then a gap, with all elements
being of 120 seconds (2 minutes) duration. This means sending a single
Q takes ten minutes. The timing was such that the start of a fresh Q
was on the hour, so coding by absolute timing was another factor that
could be used for analysis of weak signal detection. The ZL6QH LF signal
was generated using a modified TS-850SAT, in SSB mode, fed with audio
from a lap top PC, using soundcard software developed
by Steve Olney VK2ZTO. TS-850 frequency control was by means
of a high performance TCXO master oscillator. The low level LF signal
from the TS-850 transverter port was fed to an external LF power amplifier,
and the output power was around 500 watts. The radiated power is estimated
to be 4 watts. The antenna was a long wire at the Quartz Hill club station,
which is run by the Wellington Amateur Radio Club. The ZL6QH operator
was Bob ZL2CA. The next test from ZL6QH in the 136 kHz band will be
on 15 December.
Bob Vernall ZL2CA Organiser of the ZL LF DX tests.
20 December 2001: CLAIM OF ZL TO VE1 AMATEUR LF DX
On Saturday 15 December ZL6QH transmitted a low speed frequency
shift keyed test signal in the 136kHz band, as a beacon transmission
for all hours of local darkness. John VE1ZJ managed to receive and positively
identify signals from ZL6QH. The path length from ZL6QH near Wellington
to VE1ZJ in Sydney, Nova Scotia has been calculated as being 15,645
km. VE1ZJ received the LF signal using a 10 metre vertical with top
loading, high impedance pre-amplifier, low pass filter and a TS-850
receiver. The demodulated audio was fed to a computer sound card for
filtering and display of the signal using Argo software. Weak signals
were first received by VE1ZJ at 0845 UTC, which was some 40 minutes
after ZL sunset at 0806 UTC and some three hours before VE1 sunrise
at 1150 UTC. Best reception was from 1045 to 1138 UTC. Previous best
DX for ZL6QH was confirmed reception by Dexter W4DEX two weeks earlier,
over a distance of 13,633 km [see below]. W4DEX received ZL6QH
again but generally not as well as the previous time. In June and September
ZL6QH was received by VE7SL, when the test frequency was 184.4 kHz,
but since then the ZL6QH signal has not been received at all, despite
operators being ready to try for an LF/HF cross-band contact if propagation
was satisfactory at the time. The ZL6QH transmitted signal used frequency
shift keying, with 0.4 Hz frequency shift. The uniquely coded transmission
consisted of repetitive sending of QQQQQ. sent as 137.7900, 137.7900,
137.7896, 137.7900 and then a gap, with all elements being of 120 seconds
(2 minutes) duration. This means sending a single Q takes ten minutes.
The ZL6QH LF signal was generated using a modified TS-850SAT, in SSB
mode, fed with audio from a lap top PC, using soundcard
software developed by Steve Olney VK2ZTO. TS-850 frequency
control was by means of a high performance TCXO master oscillator. The
low level LF signal from the TS-850 transverter port was fed to an external
LF power amplifier, and the output power was around 500 watts. The radiated
power is estimated to be 4 watts. The antenna was a long wire at the
Quartz Hill club station, which is run by the Wellington Amateur Radio
Club. The ZL6QH operator was Mike ZL4OL. The next test from ZL6QH in
the 136 kHz band will likely be in mid January.
Bob Vernall ZL2CA Organiser of the ZL LF DX tests
NEW AMATEUR RADIO LF WORLD RECORD CLAIMED
Amateur stations in New Zealand and Asiatic Russia are laying claim to a new low-frequency world distance QSO record. Bob Vernall, ZL2CA, told ARRL this week that ZM2E, near Wellington, New Zealand, and UA0LE, near Vladivostok, Russia, completed a two-way contact during the night of March 20 on 137.70 kHz.
"The path length is estimated to be 10,311 km (6,392 miles), which is claimed as a new world record between amateur stations on LF bands," Vernall said. "For several hours signals received at ZM2E were so strong that they could be decoded 'by ear,' despite high peaks of QRN." By noting tone-on and tone-off times and checking them against a highly-accurate digital clock, the ZM2E operators at one point were able to decode the very slow-speed (QRSS) CW without resorting to Argo DSP software signal detection.
The Wellington Amateur Radio Club station at Quartz Hill uses the special ZM2E call sign for work in the 136-kHz band. A DXpedition station, UA0LE obtained permission to support its LF antennas from a 90-meter (295.3 feet) broadcast mast.
Vernall said UA0LE set up for a slow-speed CW beacon transmission on 137.7895 kHz using 60-second dits--known as QRSS60. "They used the shortened form of 'UATLE' to save time in sending," he explained. Because they need to be succinct, Vernall said, LF DX signal reports use the same "O," "M" and "T" signal reports developed for moonbounce and other weak-signal communication.
On the big day, ZM2E started calling UA0LE at 0930 UTC--sunset in Vladivostok. The first good UA0LE signals showed up on the computer screen at 1030 UTC, Vernall said.
The defining moment came when UA0LE confirmed reception of the "O" report from ZM2E. "At 1650 UTC, we received 'ZM RO E,' and by acknowledging our report to them it satisfied the minimum requirements for claiming a two-way contact," Vernall said. The two stations continued to "tie the ribbons" on the QSO for another hour or so.
Vernall and Andrew Corney, ZL2BBJ, were the operators at ZM2E. The operators in Vladivostok were Vlad Burakov, UA0LE; Vic Bondarev, UA9OC; Andy Rodichev, RA0LGH, and Ed Lesnichy, RU6LA.
A QSO took place today between the Quartz Hill club station, callsign ZM2E, and the Asiatic Russian expedition station nr Vladivostok, UA0LE. Time and date are local = gmt + 10hrs.
In this screen grab from Vladivostok you can see the end of the local
CQ call followed by a very clear "ZM2E K" on DFCW (dots are low). The
middle of the "K" has been knocked out by a tune-up by the look of it!
Here we can see the reply from ZM2E after the UA0 call.. "UA R O O K" so it seems there was an "O" copy both ways. Not bad for about 10,000km!
The following is extracted from my own VK2ZTO archive and is for historical purposes only - the software for VFSKCW is no longer distributed...
The beta version of this program is available for download below. Before downloading read the Notes: below.
From the response to the Beta version 2 release I have produced Version 3 which incorporates tone-shaping (from an observation by Dave Brown - ZL3FJ) to reduce key clicks and a help file. Subsequent requests have resulted in Beta Version 4 release which entails adding a 'wobble' option to help distinguish between consecutive tones in a run of dashes or dots.
An updated Beta Version 4 release has dots lengths of 60, 90 and 120 seconds to match the settings available on Alberto di Bene's excellent Argo program as suggested by Bob Vernall - ZL2CA. Version 5 has the provision of selecting the nominal centre frequency as well as fine tuning the output frequency to compensate for sound card sampling rate errors. In addition the Help File has been updated to reference the setting of the centre frequency.
The latest revision of Version 5 is v5.01.03.15. Check that you have the latest revision by looking at the title bar of VFSKCW when you run it. Note that you will need at least 20Mbytes of free hard disk space for the output files if you want to use 120 second tones. VFSKCW version 5 available now...
Zipped Executeable - (373 k bytes). VFSKCW05.ZIP
Download and Installation:
i. Click on VFSKCW05.ZIP above and download into a separate folder
of your choice.
ii. Unzip file.
iii. Run VFSKCW.EXE
iv. To
remove VFSKCW from your system simply delete the directory. (No system
files are altered by the installation).
v. Connections are the same
as PSK31.
Use Spectrogram on receive. You must STOP Spectrogram when transmitting.
NOTES:
i. The Version 5 program executeable has the same name as
versions 1, 2, 3 and 4. (Title of main screen gives the version).
ii. The program needs Windows 95/98 to run - it is not a DOS program.
iii. The latest versions (Versions 3, 4 and 5) include a Help file.
iv. Because the two tones are output from the Soundblaster card, you
must STOP Spectrogram while transmitting using VFSKCW (but you don't
have to EXIT Spectrogram). Spectrogram captures the Soundblaster card
when it is actively receiving data.
v. The usual disclaimer about
damages etc. apply.