Hi All,
Herewith a "Stop Press" posting for the CARC blog :
< Stop Press : The adjudicated results for The July 2010 VHF Contest
have just been posted on theRSGB VHF contest site (www.rsgbcc.org)
- - - The joint Crawley- Reigate team under the callsign G5LK/P have
achieved yet another excellent result in the 2010 VHF NFD contest
coming in overall second place in the UK open section being just
pipped by the very strong G3VHF/P Colchester ARC team who until last
year had been overall winners for the past 5 years until being
displaced from first place in 2009 by the CARC/RATS entry.
The G5LK/P team gained overall first on the very hotly contested
144Mhz band and second place on 432Mhz and third place this year on
1296Mhz after achieving first place in 2009. The results on 70Mhz and
50Mhz were a little disapointing by comparison at 7th place and 12th
place respectively, However this is a good overall result -
congratulations to all the team.
[A more comprehensive report with photographs will follow later]
de G3GRO >
More information is available at
http://www.rsgbcc.org/vhf/results/10/VHFNFD.html
Thursday, September 16, 2010
Friday, September 10, 2010
The August Meeting QRSS by Hans Summers G0UPL
On August 25th we were delighted to welcome back Hans Summers G0UPL. Hans gave CARC an inspirational talk on homebrew back in 2006, and before that time and since, has been putting in a lot of hours on QRSS.
He had given a presentation to the Four Days in May symposium at Dayton earlier this year so when Richard G4ANN, Stewart G3YSX, myself and others from Crawley were sitting in the FDIM audience it was a natural to invite him back to Crawley to reprise his talk. Now it should be mentioned that Hans was inducted into the QRP ARCI Hall of Fame at Dayton last year, and so it was quite an honour to welcome him back.
QRSS - What it is and what it does
So what is QRSS? 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 of a receiver. Morse code element lengths of 10 to 30 seconds per dot are commonly used.
QRSS enables operators to extend the range of very low power HF communications using simple low-cost home-brewed gear. This is a large part of the attraction of QRSS, and some amateurs who have got into this mode now use nothing else.
The global reach of QRSS is of course part of its fascination. This coupled with the
ability to use simple low cost home built equipment.
- Information theory (Shannon) says that the slower you send, the less bandwidth you need.
- A narrower bandwidth receiver filter means less noise gets through along with the wanted signal, leading to higher Signal to Noise ratio.
- SSB (2.4 KHz) is better than AM.
- CW is better than SSB.
- Very slow CW (QRSS) is better still!
- 12 wpm CW, occupying 10Hz: 0dB
- 8 wpm CW, occupies 6.67Hz: +1.8dB
- 4 wpm CW, occupies 3.33Hz: +4.8dB
- QRSS 1s/dot, occupies 1Hz: +10dB
- QRSS 3s/dot, occupies 0.33Hz: +14.8dB
- QRSS 10s/dot, occupies 0.1Hz: +20dB – that's 4 S-points relative to 12wpm Morse!
Some History
In 1964 RCA developed what was in effect the first emergency system using narrow band CW. Operating on around 15 MHz and with a transmitter power of 100mW to a half-wave bent dipole, the equipment was battery powered. The transmitter was crystal controlled, using a special crystal optimized for 37C and placed under the operator's armpit to maintain temperature stability! The transmit frequency swept over 20Hz in 20 seconds at a rate of 3 bits per minute. With a receiver bandwidth of 0.75Hz reliable communications was possible over 2,000 miles in daytime.
Current Design Trends
What therefore are the design parameters for today’s QRSS receiver and transmitter? The major change is in how the very narrow receive selectivity is obtained, from the use of a computer sound card rather than a crystal filter. Quite a modest PC or laptop running FFT software analyses your receiver audio via the sound card input. For this to happen you will also need suitable software, of which there are various programs available for free download, including Argo, Spectran, Spectogram, and Spectrum Lab; Argo being the ideal beginners choice.
And once you start, QRSS is addictive and it's great fun. It’s also great area for home brewing, with lots to learn about propagation, new criteria becoming important e.g. frequency stability to keep within the extremely narrow bandwidth, and frequency measurement.
Of the groups available on the web Knights QRSS group is particularly active.
A 30m QRSS Transmitter Kit has been produced by Steve G0XAR and Hans G0UPL.
Earlier this year they produced 100 kits which Hans took to Dayton FDIM.
The kits were sold out in four hours following his FDIM QRSS presentation on Thursday 13-May. It is now available again at a cost of £10.00.
Where possible the preferred method of construction is into an Ozon mint tin. These mints are available at many newsagents here in the UK. One target is a complete 20m station in a box, not just a transceiver.
Therefore the tin should contain the battery pack, Morse key, headphones and even
antenna wire!
QRSS Receiver in an O\ZON Mint Tin
The components for this project were all chosen for small size and low current consumption. Hans carried out some on-air tests during QSO's on 80m CW - the other
op re-tuned for 20m and listened for the rig, but nothing was heard. Some more work
is needed on this project.
Beaconing and Your License
Running mWatts it is tempting to run in beacon mode, although current legislation states that beacons must not be unattended. However Knights QRSS group have coined the term MEPT – Manned Experimental Propagation Transmitter - and are lobbying for “MEPT”'s to be legalized within the license conditions. In Hans opinion
these tiny powers don’t really get noticed much!
30M QRSS Beacon
Hans describes this as “A borderline insane” 30m QRSS beacon project, completely independent of computer control and containing NO microprocessors! The beacon contains an 8K EEPROM (28C64 chip) of which only 1K is used. It is programmed by hand from front panel switches. The controller is capable of the following modes:
- 12 WPM ordinary CW
- QRSS3 (CW with 3 second dot length)
- QRSS10 (CW with 10 second dot length)
- DFCW3 (dual frequency CW with 3 second dot length)
- DFCW10 (dual frequency CW with 10 second dot length
- A type of slow-Hell Schreiber
This project was/is a long series of modifications, operation periods, reports, and endless expenditure of frustration, patience and sometimes jubilation. Eventually Hans received reception reports from all around Western and Northern Europe.
These reports included Mike ZL4OL, Tjærand LA9BEA, David VK6DI, Heinz OE5EEP, Peter PA1SDB, Johan SM6LKM, Vic G3GKI, Larry WB3ANQ, Chris DL6JAN, Erik ON4LP, LA5VNA and others.
In pursuit of his final goals Hans casts his net wide and there were a numerous sub-projects included in his presentation, such as battery cells to power these small rigs.
Baked Bean cans, Orange juice bottles and Bleach. 4 Cells make a
battery.
This was a subject in itself, and explored the use of baked bean tins, lemons, orange juice bottles and containers of Azda bleach.
The use of LED s as varicap diodes was looked at in some detail, and of the built projects the small receivers and beacon transmitters, and the beacon controller were discussed in some detail. An L-Match ATU was another project in the G0UPL portfolio.
The G0UPL L-Match ATU
In addition to his home QTH Hans also took kit and operated from Granada in the Caribbean and Southern Turkey where he also received some long-range reception reports.
Within the confines of CARC On Line’s Blog pages it really isn’t possible to do full justice to the scope of Hans’ talk, and for that we strongly recommend visiting his excellent website at www.hanssummers.com
John Longhurst, G3VLH
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