Thursday, August 1, 2013

2013 Digital EME Contest

This was my first EME (earth-moon-earth) contest and I had a lot of fun but not much sleep!  The moon rose above my local hills past midnight local time, so on both days I was up the whole night long trying to make contacts.  The contest involved trying to make as many different contacts on the 2-meter (144 MHz) band as possible, using digital modes, and with one strict requirement:  all contacts must be complete two-way exchanges using only signals reflected off of the moon.

Out of the 29 QSO's, eight were new initials (stations not previously worked), including a new country (Uruguay) and two US states.  The most exciting contact was a local California station (Stanford W6YX), with very strong direct signals but also with a very weak lunar echo trace visible. Once the lunar echo was strong enough to decode, we could complete the QSO!

Below is the contest log:

Date            Time    Call    Grid    Sent    Rec'd
7/27/2013       6:50    UA3PTW  KO93    "O"     "O"
7/27/2013       7:56    I2FAK   JN45    "O"     "O"
7/27/2013       8:14    EB5EEO  IM98    "O"     "O"
7/27/2013       8:51    I3MEK   JN55    "O"     "O"
7/27/2013       8:57    DD0VF   JO61    "O"     "O"
7/27/2013       9:15    DL4KUG  JO64    "O"     "O"
7/27/2013       9:51    CX2SC   GF25    "O"     "O"
7/27/2013       10:05   WZ5Q    EM30    "O"     "O"
7/27/2013       10:18   CT1HZE  IM57    "O"     "O"
7/27/2013       10:49   K3RWR   FM18    "O"     "O"
7/27/2013       10:55   NZ5N    EL96    "O"     "O"
7/27/2013       11:06   AD4TJ   FM08    "O"     "O"
7/27/2013       13:43   K9MRI   EN70    "O"     "O"
7/27/2013       14:05   VK5APN  PF95    "O"     "O"
7/27/2013       15:01   W8WN    EM77    "O"     "O"
7/27/2013       15:25   KD9NH   EN44    "O"     "O"
7/27/2013       16:50   HL5QO   PM42    "O"     "O"
7/28/2013       7:18    HB9Q    JN47    "O"     "O"
7/28/2013       8:16    RU1MS   KO48    "O"     "O"
7/28/2013       9:01    OK1KIR  JO70    "O"     "O"
7/28/2013       9:11    UR7D    KN18    "O"     "O"
7/28/2013       9:15    F1DUZ   IN97    "O"     "O"
7/28/2013       9:44    G4SWX   JO02    "O"     "O"
7/28/2013       10:19   SM4GGC  JO69    "O"     "O"
7/28/2013       13:53   KE7NR   DM33    "O"     "O"
7/28/2013       14:00   VE1KG   FN84    "O"     "O"
7/28/2013       15:41   JA5EEU  PM63    "O"     "O"
7/28/2013       16:49   K5DNL   EM15    "O"     "O"
7/28/2013       17:36   W6YX    CM87    "O"     "O"

Here is a screenshot from a typical QSO.  This one is with VK5APN in Australia.  At 1402z you can see the trace that decoded as KB5WIA VK5APN PF95, when he replied to my CQ call.  At 1404z you can see the characteristic shorthand notation of "RO", where he acknowledged my OOO signal report.  And at 1406z you can see the shorthand notation for "73", indication completion of the QSO.  The lower left window is the WSJT9 software display from the FT-817ND analog radio, and the middle window is the MAP65 display from the FunCube Dongle Pro+ software-defined radio.

And next is a screenshot of the W6YX QSO.  In the SpecJT waterfall window, you can see the strong direct terrestrial JT65B signals clearly at about DF=80Hz.  At around -285Hz you can see a very faint trace, which decoded as KB5WIA W6YX CM87 at time 1731z.  The dT of the decoded trace is 2.0 seconds, in line with the expected 2.5-second round-trip of radio signals to the moon and back (the WSJT9 software clock is about 0.5 seconds behind the MAP65 clock, you can see this in the VK5APN windows above).  The Astronomical Data window in the upper right shows that the expected doppler shift between KB5WIA and W6YX was -369Hz at that instant.  The observed doppler shift of the faint trace is -285Hz - 80Hz = -365Hz, pretty much exactly as expected and further confirming the weak trace as a lunar echo.  Also of interest is the diagonal trace at 1733z, veering off the main sync line to the upper left; this is likely an airplane echo, doppler-shifted by the relative speed of the aircraft between the two stations.  To me, these QSO's are even more fascinating than EME DX contacts to the other side of the world -- since you can literally "see" the radios hearing signals coming direct through the air, the signals bouncing off of airplanes, and signals literally bouncing off the moon.

The MAP65 waterfall display (receiving signals from the FunCube Dongle Pro+) was really useful -- it helped to keep an eye on what signals were strong enough for easy decodes, and at times the messages display was full of QSO information.

All in all, it was a fun contest!  I'm pretty happy to make 29 unique QSO's via radio signals reflected off the moon, all in a single weekend!

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