The details for March 7, 2016 can be viewed here.
This session was another perfect storm situation, so to speak, as geomagnetic storm levels were observed again and terrestrial storms increased QRN and lightning risk for transmitting and receiving stations alike. Stations in the Northeast were subjected to another ice storm. It seemed like a lean session but seemingly very high receive station activity. Today’s report will likely be short and sweet.
Geomagnetic conditions continue at unsettled levels with a late afternoon peak to storm levels. The Bz continues to show variability but has remained near the centerline through the excursions. Solar wind velocities approached 600 km/s but decreased this morning, averaging 580 km/s. DST levels continue to suggest disturbed band conditions although the Kyoto index seems to be somewhat more optimistic than the Australian index. Unsettled conditions continue for now.
There were no trans-Atlantic reports during this session.
Chris, G3XIZ, reported that PI4DWN was calling CQ on 472.5 kHz at 1245z. Chris called the station but received no response. Noise is probably elevated everywhere. Tis’ the season.
Paul, N1BUG, reported that the session started out quiet but became very noisy as darkness moved West. He decoded nine WSPR stations overnight.
Al, K2BLA / WI2XBV, reported high noise during the evening but indicates that QRN was slightly improved this morning. Al was decoded by 25 unique stations including WH2XCR and two VE7 stations. He decoded six WSPR stations.
Rick, W7RNB / WI2XJQ, reports that the session was poor with only a few reports making it into the upper Midwest during the session, which is remarkable in and of itself given the noise emanating to the South of the region. Rick provided reports for seven WSPR stations and was decoded by 29 unique stations and indicates that coverage from Alaska to San Diego and Hawaii were strong. Rick’s unique report details can be viewed here.
John, VE3EAR, reported on LOWFER, “For the second time this season I’ve logged ZF1EJ in WSPR-2 mode. It’s nice to get a decode from a station off the continent, but I’m still after that elusive T/A.”
Larry, W0OGH, located in Arizona, reported that band conditions were poor with high noise. Larry reported seven WSPR stations (287 decodes) between 0336z and 1500z. Larry’s statistics follow:
After 1324Z only WH2XXP & WH2XGP were captured
0336Z WH2XXP -1 DM33, 115 captures
0340Z WH2XGP -26 DN07, 83 captures
0610Z WI2XJQ -24 CN87, 28 captures
0752Z WD2XSH/15 -25 EM34, 30 captures
0826Z WH2XCR -25 BL11, 16 captures
0922Z WG2XSV -17 CN85, 12 captures
1022Z WI2XBV -18 EL99, 3 captures
Trans-Pacific report details, excluding KL7 and KH6, can be viewed here.
Roger, VK4YB, indicated that “Propagation had a similar pattern to last night, but much weaker, with fewer spots and the return of moderate QRN. 630m/160m tests with VE6XH continue, 160m 7 spots, best -18, 630m 3 spots, best -27.” He received reports from VE6XH, VE7BDQ, and VE7SL. He provided reports for WH2XGP and WH2XXP.
Ward, K7PO / WH2XXP, received reports from 59 unique stations including JA1NQI, VK4YB, and ZL2AFP.
Larry, W7IUV / WH2XGP, provided reports for 42 WSPR stations and was received by eight unique stations including VK4YB and ZL2AFP. As W7IUV, Larry provided reports for six WSPR stations.
Joe, DF2JP, reported wind problems so his evening and overnight kite antenna experiment has been scrubbed. He will reschedule as soon as the winds permit.
Because of approaching storms, I briefly called CQ on 474.5 kHz CW starting around 0048z as the station was configured for CW from my activity yesterday morning. QRN was high and while I switched receive antennas almost constantly, no additional stations or QSO were reported. I secured the stations shortly after 0100z. I expect to be QRV tonight as the weather system has passed. I may start on CW, transitioned to WSPR later in the evening.
Regional and continental WSPR breakdowns follow:
Eden, ZF1EJ, provided reports for seven WSPR stations and was reported by nineteen unique stations including two-way reports with WH2XCR.
Laurence, KL7L / WE2XPQ, received reports from JA1NIQ during the pre-dawn period of this session and continued up to sunrise. He also provided reports for VK4YB and shared two-way reports with WH2XCR. Attenuation continues making for difficulty in moving signals into and out of Alaska. DX report details can be viewed here.
Merv, K9FD/KH6 / WH2XCR, experienced a relatively consistent session compared to recent nights, sharing two-way reports with VK4YB, WE2XPQ and ZF1EJ while receiving reports from ZL2AFP, 7L1RLL4, JA1NQI, PA1PKG, JE1JDL, and JH3XCU. North America was limited by noise, particularly in the central and eastern US although WH2XZO provided reports for Merv which is remarkable given the level of storm activity to Doug’s West and Northwest. WI2XBV was reported by Merv but that report may have come this morning as Al reported that he shut his station down overnight due to QRN. Merv’s DX report details can be viewed here.
Jim, W5EST, presents, “GET A GRIP ON 630M GROUND WAVE”:
“When it comes to ground wave, perhaps you’re like me – I’ve spent most of my radio life simply taking for granted that there’s ground wave and there’s sky wave, and each act in their own ways. From a reception point of view, I just think of ground wave as what’s about same signal strength day and night on a short path and what’s daytime strength on a non-prop-event daytime at somewhat farther distances. One can receive ground wave, say, within a few hundred kilometers of a TX station especially on LF/MF.
Today, let’s see if we get some deeper insight into what ground wave is and how it works. If you have better information and additional reference citations, please send them for this blog!
In today’s illustration, I plotted daytime 630m morning receptions March 6, 2017, at various distances out to 1200 km. On the WSPR database, SNR for a given path stabilizes about an hour after eastward station sunrise. I determined and plotted the median SNR for daytime decodes (Endnote 1*) by each receiving station vs. path distance after adjusting for TX power dBm of whatever TX station across the USA was being decoded.
Naturally there’s a great deal of numerical uncertainty introduced by different ops’ TX power estimation plus inherent variation in RX antennas and intervening terrain resistivity along the paths. Band noise variations, not to mention local artificial QRN, further vary the SNRs even though I used a Doppler radar web site to avoid confusing nearby storm effects with good SNR data indicative of signal strength.
A family of theoretical power-adjusted ground wave loss curves (Endnote 2**) correspond to various amounts of equivalent loss fraction per path kilometer. The theoretical curves are overlaid as illustrated on the actual 630m information derived from the WSPR database (spreadsheet available on request).
GW Path Loss (dB) ~ = – 4.34 ε (r2 -r1) – 10 log10 (r2 / r1) dB
ε is a ground loss dissipation constant roughly centered at 0.5%-per-km and spreads between 0.1% / km and 1.0% / km as shown in blue. Its value probably depends in general on LF/MF frequency band in use as well as terrain of a path. The log distance ratio term tells us that every doubling of distance involves 3dB more loss, which means more steeply significant ground loss per km at closer distances to the TX station. Since the formula compares dB between different distances instead of predicting power-adjusted SNR data vs. distance, I positioned the path loss curves up and down vertically on the illustration to encompass most of the data points.
What does all the information mean? I think it tells us that 630m TX station operators are not only quite willing to run their stations 2-3 hours after sunrise; they do so. About 22 RX operators are out there actually receiving daytime 630m transmissions in North America, and that’s probably a conservative estimate. GL with your 630m daytime experiments!”
* Endnote 1: These were morning limited-time SNR numbers, and a trend into midday SNRs might also be present especially at the longer distances, http://njdtechnologies.net/022217/ . Median morning SNR is used as a proxy for g.w. signal strength here. Morning SNR variations ranged ~6-8dB on most of the paths exceeding 600 km. If ground wave interfered with sky wave to cause the variations, then g.w. strength was similar to sky wave strength at those longer distances, and the median roughly measures the g.w. component. If band noise caused the variations instead, the median is still a reasonable if imperfect comparative g.w. strength measure.
** Endnote 2: Ground wave power density p(r) at any particular radius r is the total radiated ground wave power p0 divided by the circumference of the g.w. wavefront at that radius:
p(r) = p0(r) / 2πr
The rate of change of power density p(r) versus radius has a first negative component due to the distribution of the radiated power over an ever-increasing circumference of the wavefront, and a second negative component due to the power losses in the dissipative earth on which the wave travels. Taking a derivative gives:
d/dr (p0(r)/2πr) = -p0(r)/2πr2 + (1/2πr) d/dr(p0(r))
Assume that uniform ground conductivity dissipates a small fraction ε of the total power reaching any particular radial distance r so that d/dr(p0(r)) = – ε p0(r). I assume the fraction per km is constant as the wavefront tilts https://en.wikipedia.org/wiki/Surface_wave#Radio_propagation
(scroll ¼). But its constancy is certainly not exact over nonuniform ground and possibly not exact over even uniform ground in a rigorous electromagnetic math solution. In terms of power density at distance r, rewrite by substituting p(r) = p0/2πr:
d/dr p(r)= –(1/r)p(r) – ε p(r). ( ε is assumed constant)
Divide both sides by p(r):
(1/p(r)) d/dr p(r) = –(1/r) – ε .
Integrate both sides from one radius r1 to another radius r2 :
ln p(r2) -ln p(r1) = -(ln r2 – ln r1) – (ε r2 – ε r1)
Exponentiate and simplify by recognizing properties of logarithms and e=~2.71828, the base of natural logarithms:
p(r2) / p(r1) = r1 / r2 e – ε (r2 -r1)
Convert to dB path loss:
GW Path Loss (dB) = 10 log10 p(r2) / p(r1) = 10 log10[ r1 / r2 e – ε (r2 -r1) ]
Rewrite as a sum of dB:
GW Path Loss (dB) = -10 log10 (r2 / r1) – 4.34 ε (r2 -r1)
where 4.34 is 10 log10(e).
Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD gmail dot (com).