Tropospheric Propagation Phenomena

VHF/UHF WSPR - Tropospheric Propagation Phenomena

11 June 2012 0700 UTC - N6GN signals tonight are up to -10 dB SNR, after the winds have calmed, I suspect we are now seeing some enhancement from the tropo predicted by Hepburn.

7. 11 June 2012 0700 UTC - N6GN signals tonight are up to -10 dB SNR, after the winds have calmed, I suspect we are now seeing some tropospheric enhancement predicted by Hepburn on http://www.dxinfocentre.com/tropo_wam.html3


Hepburn Tropo Index 1200 UTC June 14, 2012.

8. Hepburn Tropospheric Index 1200 UTC June 14, 2012.


Hepburn Tropo Index 1200 UTC June 15, 2012.

9. Hepburn Tropospheric Index 1200 UTC June 15, 2012.


10. WSPRnet Spot Reports of KP4MD Signal to Noise Ratio (SNR) at N6GN June 11-17, 2012. Compare with the previous Tropospheric Forecast Maps for those dates. The dip in signal strengths on 15 June appears to coincide with the absence of tropospheric enhancement over the signal path on that date.


Early morning heating of the upper troposphere over a valley as a source of propagation enhancement. The temperature inversion at the boundary of the warm air and the cool air can support VHF and UHF radio wave propagation to hundreds of kilometers beyond the line of sight.

11. Early morning heating of the upper troposphere over a valley as a source of propagation enhancement.4 The temperature inversion at the boundary of the warm air and the cool air can support VHF and UHF radio wave propagation to hundreds of kilometers beyond the line of sight.


View from 5500 foot elevation in the Sierra Nevada Mountains of a temperature inversion over the San Joaquin Valley in central California.

12. A view from 5,500 feet elevation in the Sierra Nevada Mountains of a temperature inversion over the San Joaquin valley in central California.


The circuit between KP4MD in Sacramento and KI6STW in Milpitas is usually blocked by a ridge of mountains near KI6STW

13. The circuit between KP4MD in Sacramento and KI6STW in Milpitas is usually blocked by the Monument Peak mountain ridge near KI6STW.


Monument Peak, Mt. Allison (2700 ft elevation) and Mission Peak are 3 miles away from KI6STW and lie directly in the path toward Sacramento

14. Monument Peak, Mt. Allison (2700 ft elevation) and Mission Peak are 3 miles away from KI6STW and lie directly in the path toward Sacramento.


15. On 2 July 2012 KP4MD's 144 MHz WSPR signals at KI6STW were up from -28 at 0216 UTC peaking to -19 dB SNR at 0500-0700 UTC, concurrent with Hepburn's forecast predicted tropo enhancement in the Sacramento Valley at 0600 UTC.


2 July 2012 0000 UTC - Tropo forecast before enhancement event. http://www.dxinfocentre.com/tropo_wam.html

16. 2 July 2012 0000 UTC - Tropo forecast before enhancement event.
http://www.dxinfocentre.com/tropo_wam.html


2 July 2012 0600 UTC - Tropo propagation enhancement forecasted in the Sacramento valley at the time KP4MD signals peaked at KI6STW. http://www.dxinfocentre.com/tropo_wam.html

17. 2 July 2012 0600 UTC - Tropo propagation enhancement forecasted in the Sacramento valley at the time KP4MD signals peaked at KI6STW. http://www.dxinfocentre.com/tropo_wam.html


2 July 2012 1200 UTC - Tropo propagation enhancement in the Sacramento valley abated concurrent with the decline of KP4MD signals received at KI6STW. http://www.dxinfocentre.com/tropo_wam.html

18. 2 July 2012 1200 UTC - Tropo propagation enhancement in the Sacramento valley abated concurrent with the decline of KP4MD signals received at KI6STW. http://www.dxinfocentre.com/tropo_wam.html


4 July 2012 - First 144 MHz WSPR contacts established over 290 mile circuit with KC6KGE in Taft, California

19. 4 July 2012 - First 144 MHz WSPR contacts established over 290 mile circuit with KC6KGE in Taft, California.


5 July 2012 - Further 144 MHz WSPR contacts established with KC6KGE in Taft, California

20. 5 July 2012 - Further 144 MHz WSPR contacts established with KC6KGE in Taft, California.


19 July 2012 - Strong 2 meter WSPR signals received at KP4MD from KC6KGE in Taft, CA 265 miles away. Hepburn predicted tropospheric enhancement around station KC6KGE in Taft, California at 1800 UTC on 18 July and again at 0600 UTC on 19 July

21. 19 July 2012 - Strong 2 meter WSPR signals received at KP4MD from KC6KGE in Taft, CA 265 miles away. Hepburn predicted tropospheric enhancement around station KC6KGE in Taft, California at 1800 UTC on 18 July and again at 0600 UTC on 19 July.


22. 18 July 2012 - KC6KGE's 144 MHz WSPR Signal to Noise Ratio at KP4MD was up from -33 dB at 1040 UTC peaking to -18 dB SNR at 1726 UTC, and again to -10 dB at 0314 UTC on 19 July 2012.


18 July 2012 - Hepburn predicted tropospheric enhancement around KC6KGE's area on 18 July 2012 at 1800 UTC. http://www.dxinfocentre.com/tropo_wam.html

23. 18 July 2012 - Hepburn predicted tropospheric enhancement around KC6KGE's area on 18 July 2012 at 1800 UTC. http://www.dxinfocentre.com/tropo_wam.html


19 July 2012 - Hepburn predicted tropospheric enhancement around KC6KGE's area again on 19 July 2012 at 0600 UTC.

24. 19 July 2012 - Hepburn predicted tropospheric enhancement around KC6KGE's area again on 19 July 2012 at 0600 UTC. http://www.dxinfocentre.com/tropo_wam.html


REFERENCES

  1. Aircraft Scatter (ACS), Larsson I, SM6FHZ
  2. WSPRnet.org
  3. Hepburn's Tropospheric Ducting Forecasts
  4. California Temperature Inversions, Iacobellis et al.
  5. 144 MHz Propagation Study across the Alps
  6. 144 MHz WSPR Operations in Australia

LINKS

  1. 2 Meter WSPR Discussion Group
  2. 144 MHz WSPR Study Photo Album
  3. 144 MHz WSPR Study Spot Database
  4. 144 MHz WSPR Study Videos - KP4MD
  5. 144 MHz WSPR Study Videos - KC6KGE
  6. 144 MHz WSPR Study Videos - N6GN
  7. 2m WSPR (Radio Stability (M1GEO)
  8. Australian 2m WSPR Group
  9. Idiot's Guide to 144 MHz WSPR (VK3BQ)
  10. WSPR Propagation Study Paths Map
  11. Google Earth KML File
  12. Current WSPRnet 144 MHz Spot Reports
  13. WSPR Spot Report Analysis Spreadsheet with Charts

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