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Digital VHF Weak Signal Modes

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1 Digital VHF Weak Signal Modes
Gary Sutcliffe, W9XT Ken Boston, W9GA This was part of a talk on VHF/UHF operating with W9GA and W9FZ on VHF and microwave operation at the 2012 Amateur Electronic Supply Superfest. My part of the talk concentrated on the WSJT digital modes.

2 Esoteric “Space” VHF Propagation Modes
Want to make distant contacts beyond “normal range” Aurora - bounce off northern lights 6 & 2M, mostly CW, “Donald Duck” on SSB Meteor scatter – bounce off ionized meteor trails Mostly 6 & 2M, SSB, WJST Popular during meteor showers Moon bounce (EME) – use moon as a reflector 6M & up, CW, SSB, WJST 2M most popular band W9XT – DXer at heart, like to work unusual propagation modes – Find these mode interesting – Maybe because of interest in Astronomy. Aurora – point your beam north when there is an aurora. Very raspy sounding on CW. SSB may be uninteligble. Meteor scatter – bounce off shooting stars Used to be SSB with 15 second transmit periods, needed several long bursts. Heard lots of pings (very short bursts). Low success rate except during best meteor showers Some HSMS – record and play back slowed down, now mostly WJST Moon bounce Required huge antennas and high power. WSJT lowers the bar. Talk will concentrate on MS and EME

3 WSJT – Weak Signal Joe Taylor
Written by K1JT – Joe Taylor 3 Modes JT6M – Scatter on 6M FSK441 – Meteor scatter JT65 – Moon Bounce Each mode optimized for that type of operation JT6M – weak signals from scatter FSK441 – short bursts, Doppler shift JT-65 – Very weak signals, slow fading, slow Doppler shift The WSJT modes revolutionized VHF weak signal work. Use the PC with DSP. DSP allows digging deep into noise for signals on RX. On TX PC generates the modulating signal. Some of the techniques are used by NASA for communicating with deep space probes.

4 What do you need? Stuff you have Stuff you need to get
VHF Transceiver – must have SSB mode Antenna PC Stuff you need to get PC/Rig interface (inexpensive – build or buy) WSJT program – Free download! A ham with a basic station can start using them within a couple of hours for $25

5 Sound Card Interface You want to isolate the rig from the PC. RX signals are very weak, TX low level audio, easy to get ground loops and hum. You can build your own. Unified Microsystems SCI-6 Kit. $25 Unified Microsystems SCI-6 Sound Card Interface Schematic

6 WSJT Software Free down load
Standardized QSO formats – not a rag chew mode Step by step defined sequences 30 or 60 second transmit/receive periods Requires synchronized PC clocks

7 WJST User Interface Similar in all modes
Upper – Received signal display – varies with mode Center – Decoded signals Lower left – Set up – station & Grid Date/time – WSJT records RX signal as wave files. These are play backs – date & time is when slide made, not wav file date Lower center RX configuration settings Lower right: Transmit sequence exchanges

8 WSJT QSO Sequence Stations alternate 30 or 60 sec. transmissions:
Station 1 Transmission Station 2 Transmission CQ W9XT EN53 W9XT W1XYZ GRID W1XZY W9XT RPT R RPT RRR 73 FSK441 and JT6M use 30 second transmissions. JT65 uses 60 second transmissions For a QSO to be valid: Both calls copied by both stations Signal reports exchanged and acknowledged. You keep sending the same thing until you copy the next step in sequence, then go to the one after that. Report differs with mode. WSJT reports are based on report types used before WSJT – S2 was used for SSB MS, TMO for CW EME

9 Meteor Scatter Meteor burst
Several milliseconds to maybe 30 seconds, short ones much more common Longer on 6M, short on 2M, very short 222 MHz Maybe 1 burst per minute visible during a good shower Maximum range out to about miles. Station Requirements 50-100W good, more is better Medium sized antenna best High gain antennas too narrow – don’t know exactly were meteor will appear In the old days of SSB work – 15 second transmit periods. Took a number of long (5+ second) bursts for complete QSO. Heard lots of pings – short bursts with single word heard WSJT is high speed. Calls and report can get through in ¼ (250 msec) ping. Moderate station is fine. Don’t need elevation on antenna.

10 FSK441 – Meteor Scatter The call signs of both stations were received multiple times from a single 360 msec burst. Once worked a station in FL. He had a home brew coat hanger 4 element yagi on step ladder and 15 watts. Since FSK441 can get the information through on such short bursts, don’t need a meteor shower. Lots of contacts are made using random meteors.

11 Moon Bounce Signal path Station Requirements
Round trip to moon and back ~2.4 seconds. 250 dB loss Station Requirements 100W single long Yagi minimum – work a few really big stations 350W, 4 Yagis with elevation – can work equivalent stations Need to track moon Az-El Meteor scatter is only good out to 1400 miles or so. What do you do if you want to work stations further away. Need something else to reflect the signals back to earth. The Moon! 250dB is huge. That is what make EME perhaps the most difficult QSO in ham radio. Difference between 1KW and 0.1μW is only 100dB, 2KW and 0.1μW is 103 dB. 10KW and 0.1μW is 110dB.

12 JT65 – Moon bounce Blue line is the time difference – know it is off the moon Red line is the sync line – nice narrow spike is good. Green line is just noise. Upper left moon info. Note at time slide was made the moon was below horizon. The signal and decoded data windows are from a recorded wav file of QSO with DK1CO. This was a good copy and it was 23 dB under the RX noise. A very strong signal!

13 W5UN This is a very large EME station. Many beginning EME ops have their first QSO with W5UN. In my first QSO with W5UN the amplifier blew up half way during QSO. QSO finished with 50W and single 13 El yagi with no elevation.

14 W9XT “QRP” EME Station Equipment: Yaesu FT-847 All mode transceiver
Mirage B2518G 150W 2M amp Cushcraft 13B2 13 element Yagis (2) CATV 75Ω hardline Dell PC running XP Unified Microsystems SCI-6 PC I/F Plans for 2012: Increase to 4 Yagis KW amp

15 W9GA EME Station Equipment: 144 system:
Kenwood TS-711 2M All mode transceiver Henry M 700 W amp 2 X 9 el M2 Yagis, hand aimed (not shown) M2 preamp Laptop PC 50 MHz system: Yaesu FT1000MP mkV w/FTV1000 H.B. KW amp with a pair of 3CX800s 2 X 6M5X vertically pol, with elevation PC with WSJT Antennas on 144 similar to W9XT, but are set up for temporary use on a mast on back porch. 50 meg system permanent, and used also on E skip. Although 50 meg antennas are vertical, they work well on E skip (and F2) due to ionospheric rotation. Not so good on tropo however.

16 50 MHz EME antenna 50 Megahertz; pair of vertical polarized M2 5 elements, with elevation via rotor and crank. Tropo antennas for higher bands in middle

17 QSLs received Left and center column are 144 EME qsls; right column is 50 EME qsls.

18 Scatter Modes Lots of propagation modes
F2 – Regular HF propagation mode if high solar levels Es - Common in spring months JT6M lets you make contacts when there is not enough signal to make CW & SSB QSOs I have not used this mode very much. There are other ways to make contacts, but many 6M ops really like it.

19 JT6M – Scatter modes (6M) This is from an attempt to work K7BV. I copied him fine but I had high SWR on my antenna and the rig cut back power. We never made the QSO. The burst was probably from a small meteor. JT6M will also work with meteors as well as other scatter propagation.

20 Ping Jockey A lot of schedules for WSJT modes are made on Ping Jockey.

21 Slide deck will be put up on
WSJT Resources WSJT Download: N0UK Ping Jockey page: Unified Microsystems: Inexpensive PC sound card to radio interface kit ON4KST chat page: Slide deck will be put up on WSJT Summary Lot of fun Technology available only to NASA 10 years ago. Enables small stations to make contacts only big guns could do before

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