VHF/UHF WSPR Propagation Study
Observations of Radio Propagation above 50 MHz using Dr. Joseph Taylor's WSPR (Weak Signal Propagation Reporter)
by Dr. Carol F. Milazzo, KP4MD (posted 14 June 2012) last update 21 Nov 2020 E-mail: firstname.lastname@example.org
Check William Hepburn's Tropospheric Ducting Forecasts for current VHF propagation conditions.
Propagation Study Paths
View 2 meter WSPR Propagation Study in a larger map
2. WSPR Propagation study paths. W7PUA-N6KOG 482 miles from NW Oregon to the central California valley. N6GN/K6PZB-KC6KGE 292 miles over coastal range summits. N6KOG-N3IZN 385 miles through central California valley and over San Bernardino Mountains. Interactive map link Google Earth KML file
3. The Radio Mobile Online application produced this combined coverage map for the West Coast 2 meter WSPR study group stations. At least one of our stations should be heard on 144.4905 MHz at locations from Southwest Washington state through California from Redding to the Grapevine and to San Diego. The expected signal to noise ratio is greater than -20 dB in the yellow areas and less than -20 dB in the orange areas.
4. Northern California Stations in 144 MHz WSPR Propagation Study. The path distances between Sacramento (KP4MD-WW8L), Santa Rosa (K6PZB-N6GN) and Milpitas (KI6STW) are similar. There are no apparent high elevations obstructing the path from Santa Rosa to Milpitas. Mt. Allison (Elev. 2664 ft) in the Monument Peak Ridge is 3 miles away from Milpitas and directly obstructs the path to Sacramento. The Sugarloaf Ridge and Blue Ridge-Berryessa areas average 1800-2000 ft elevation and obstruct the path from Santa Rosa to Sacramento.
5. 6 June 2012 - N6GN WSPR signals received at KP4MD. The steep diagonal traces on the waterfall are reflected signals from passing aircraft subject to Doppler shift.1 N6GN has observed that Doppler reflections near the signal frequency for about 20% of each two minute transmission window often cause WSPR signal decoding failure.
6. Time lapse screen captures of contacts among 144 MHz WSPR propagation study stations. All spot reports consisting of time, signal to noise ratio, time segment shift, frequency and drift received at the study stations are uploaded to a database at WSPRnet.org.2
Tropospheric Propagation Phenomena
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
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.
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.
25. 12 July 2012 - On http://planefinder.net N6GN noticed a FedEx flight, southbound on a path that took it about 8 miles east of Santa Rosa at about 13K feet. The plane took a turn to the east, starting about Petaluma on this path.
26. 12 July 2012 - When the FedEx plane flew overhead at 0444 UTC, a trace from KI6STW shows such a strong aircraft scatter (ACS) component that it didn't decode. Furthermore, the reason for the lack of decode was that the ACS components were quite close to transmitted frequency for a significant portion of the 2 minutes, particularly at the start. Since this aircraft was flying almost exactly along the path between the two stations, the indirect path length wasn't changing much. As the turn progressed, the path started getting longer to both N6GN and KI6STW from the aircraft and the ACS (Doppler) component dropped in frequency.
27. 12 Aug 2012 - 0725 - 1430 UTC - 144 MHz WSPR Study (Perseid Meteor Shower) A few very bright, long and steep descending Doppler echoes at 0726 and 0758 are probably aircraft scatter (ACS). The much shorter duration traces at 0916, 1052 and 1138 may be meteor echoes. The ACS echoes increase rapidly after 1250 due to local air traffic.
Aircraft Wingtip Vortices
30. 02 Oct 2012 1338 UTC - Spectran analysis of the final 80 seconds of a 2 meter WSPR signal showing the discrete tones. This signal did not decode due to the 25 Hz negative frequency drift over the period. Moving symmetric side images 35 dB down from main signal are observed. The corresponding WSPR waterfall segment is on the right.
31. N6GN engineered this GPS disciplined frequency reference for selected stations in our West Coast VHF/UHF WSPR Study Group. It provides a 10 MHz reference as well as a GPS disciplined substitute for the master oscillator or local oscillator of various commercial transceivers or transverters. The discussion thread can be read here. Leo Bodnar Electronics now sells a similar device.
32. A typical Elecraft XV144 transverter modification for the GPS10V frequency reference. The 47Ω resistor suppresses the 116 MHz crystal oscillations and Q1 functions to amplify the external 116 MHz reference signal.
33. The Elecraft XV144's internal local oscillator with crystal oven option had exhibited 3-4 Hz frequency drift during 2 minute WSPR transmissions and long term frequency instability with ambient temperature variation. This frequency instability and drift was eliminated with the GPS10 frequency reference.