Its not too often that I don’t report at least one stations during the session. Storms made listening almost impossible here in Texas, even resulting in the scrubbing of my morning CW sked. Paths to quiet areas were good, however, so propagation was there.
Geomagnetic activity is elevated but quiet levels although the Bz is pointing to the South and solar wind velocities exceed 600 km/s in conjunction with a geoeffective coronal hole. DST values have been negatively impacted:
Phil, VE3CIQ, started the session with storms but had a nice finish with transcontinental reception reports:
“Turned up the gear right after the storm passed over, didn’t expect the receive side would work this well. Tx side was was surprisingly good as well for reduced power.”
Roger, VK4YB, reports very quiet band conditions with “noise levels at -85 dbm, about 3 dB higher than yesterday but still quite good.”
David, VK2DDI, reports four early decodes of WH2XCR, the best at -20 dB with low noise conditions in VK2.
Neil, W0YSE/7 / WG2XSV, reports that he decoded VE7BDQ, VE7SL and WH2XGP and was decoded by WE2XPQ 4 times, VE7BDQ, VE7SL, and WH2XGP.
Larry, W7IUV / WH2XGP, reports that he decoded five WSPR stations and was decoded by thirteen unique stations. No VK stations reported his signal during this session and Larry feels like conditions in the Pacific Northwest were poor.
Steve, VE7SL, also reports marginal conditions in British Columbia due to no open path to WH2XCR. Steve reports that he decoded five WSPR stations and was decoded by five unique stations.
Regional and continental WSPR breakdowns follow:
There were no reports from the trans-Atlantic, trans-African, and trans-Equatorial paths.
In the Caribbean, Eden, ZF1EJ, reported my stations:
Laurence, KL7L / WE2XPQ, had a much better session, reporting a number of stations in the Pacific Northwest and WH2XCR in Hawaii:
Merv, K9FD/KH6 / WH2XCR, experienced a more challenging path to the higher latitudes but continues to see persistent results to Oceania:
Jim, W5EST, presents “PART 2: THE DIODE EFFECT, FACT OR LORE ON 630M & OTHER WISDOM”:
“Today’s dialog summarizes the e-mail conversation I was privileged to have with Laurence WE2XPQ after he wrote in recently. Some points in 2015 from e-mails between John WG2XIQ and me are included as if part of the same conversation.
Laurence XPQ: Alaska’s ionosphere is often disturbed or at least more “sick” than at mid latitudes…most of the time I’m fighting additional attenuation. I’ve seen Oregon’s Rudy WD2XSH/20 here at 9+ CW but most of the time he’s -10 on WSPR.
Suppose I transmit (all things being equal) the same ERP into the ionosphere, say a launch site 5Kms up, that way clearing Earth effects and ground losses into the ionosphere above AK. The question is this–Will the received level in Arkansas AR be the same as if you did the same in the opposite direction. Does my disturbed ionosphere for the first say 1000Kms “attenuate” my signal more in one direction so as its weaker, than if you launch the same from your QTH? That is, even though your transmit signal has a cleaner start and then only encounters more loss for the final 1000 kilometers? Or would the signal levels be the same? Do I get more loss on the AK to AR path than you would on the AR to AK path. Eliminate solar or local QRN from the equation, eliminate East/West changes in field losses.
Jim w5est: Big reciprocity question! Diode effect–so much to learn about it. Combined TX power P and antenna gains G on the path each way would need to be comparable to test whatever answer one gives.
PTX1 + GTxAntenna1 + GRxAntenna2 ~= PTX2 + GTxAntenna2 + GRxAntenna1
Preferably the band noise at the stations’ receivers RX1 and RX2 would be nearly the same as well. Otherwise, the WSPR decoder’s threshold itself introduces a diode effect in the sense that Station 1 could decode Station 2 but Station 2 could not decode Station 1. What’s your experience?
Laurence XPQ: I have seen the diode effect on HF especially from this latitude and up to 87°N. latitude and especially when working across two sections of the Auroral curtain – where the initial launch point is very close but South of the first section of Oval. But I think for MF what seems like diode effect is mostly noise and or path/local parameters.
Working to and from the East coast on any LF, MF, or HF back to the East coast from here is very difficult. For the same distance the more pleasant path goes to NM and TX. I cannot launch a signal in most directions except VK/KH6/BY that really isn’t below 6 degrees in elevation. But most of those paths have a reasonable probability of low angle path merit instead. Only on the days when we have a mix of rays of more “mid” and “higher” multihop do I appear to do well DX-wise. Akin to last night where my 10ft loop was far superior to the E-probe that’s normally better on average. Also, in reality the first 10 miles are over poor ground. So low angle radiation isn’t my forte here!
Jim w5est: Regarding your reciprocity or diode e-mail, I answer from several angles but based on a lot less experience than yours. First, as far as I know, a short answer says that theoretically for antennas in free space, the SNRs for transmissions at the same time will be the same by a reciprocity theorem based on Maxwell’s equations. Reciprocity applies even if the antennas have different radiation patterns. If the transmissions are not simultaneous, the physical conditions of the path need to be precisely identical at the forward and reverse transmission times.
Second, a longer answer confronts questions like: What happens when the ionosphere is involved (RF interacting with dissipative plasma having imperfectly uniform contours, particles raining down, not to mention auroral absorption)? What about Faraday rotation due to the geomagnetic field permeating that plasma? Then what’s the effect on the hypothetical signals going in their opposite directions ? What about the O and X waves and gyrofrequency in all this? Again, as far as I know, the reciprocity theorem still applies even though the geometry, etc, is messy. The whole path is a linear system and reciprocity is a linear system property. But perhaps I’m not understanding the theory right, or it doesn’t apply to our reality?
The ionosphere can go nonlinear if the transmit power is strong enough and/or frequency is low enough. VLF/ELF can greatly speed up free electrons at altitude. What’s called the “Luxemburg effect” was path nonlinearity observed with very powerful broadcast stations in Europe. On 475KHz with our low EIRP and weak signals because of long paths like TA, and New England to Hawaii, I just can’t believe we’re driving the ionosphere nonlinear.
Third, A further answer says that with WSPR and JT9 you aren’t receiving the other station when you are transmitting, and propagation variations can make the SNRs different in their nearby time slots. Band noise sources will be differently distributed geographically and may be stronger at one station than another, making the SNRs almost certainly differ somewhat. But you knew all that already. Yesterday’s blog gave a XGP-XJM JT9 vignette where that may be exactly what happened over a first few minutes and then straightened itself out a few minutes later and they completed the QSO. If so, you could call that a diode effect or a nonreciprocity for our 630m practical purposes without inconsistency with antenna and propagation reciprocity in the theory. But what was weird there was that the blogged instances had persistence and hardly appeared to be due to 1-minute QSB or 2-minute QSB going in and out.
Fourth: Last November on some low-noise nights, I also tried to approach the path/reverse-path question statistically to see if the spread of SNRs on 630m is different as between the forward and reverse paths between stations. The WSPR database was sufficient to let me observe the SNR spread encompassing the middle 50% of decodes ranked by SNR. Computing SNR difference numbers that way, antenna variations and local QRN differences get mostly cancelled out. I looked at 1-hop paths in the lower 48 states and generally the SNR spread was the same each way. This was not always the case, however. I inquired in a couple of cases and found that often some change in local QRN was happening overnight at one of the stations that widened the SNR spread, like a noisy TV being used in the evening and not the rest of the night
Laurence XPQ: Most if not all of my diode experiences are on HF, and if not all have been with the diode reverse-biased on my side! …I receive very well but I believe most of the issues are related just to higher receive noise levels at the far end. But perhaps some other issue is attenuating my launch signal at low angles. And somehow the incoming rays aren’t attenuated as much as they have a ride on the last hop at some wave angle that exceeds the mountain cutoff (knife edge) inbound. But this angle isn’t attainable by my transmit array for some reason… I’m postulating.
Jim w5est: Speaking of antennas, what can you say comparatively?
Laurence XPQ: The issue of the E-probe RX signal being better (S/N) for the first 20 minutes at sundown compared to the 10ft LNA’s multiturn loop is and remains intriguing. I’ve seen this from East coast 74kHz and now from Arizona’s WH2XND. On other bands my E-probe reigns supreme. I’ve yet to place and build a loop array that beats them. But as we know it’s all related to location, local magnetic/electric field (near/far). For this location the probe wins – simple as that. Except (!) of course in relation to high level specular noise levels from one direction which isn’t in the plane of the loop and can be nulled out. That situation I have at 74kHz.
Jim w5est: Do you know of any literature that supports something like the diode effect?
Laurence XPQ: West-to-East being better than East-to-West is of interest to see if reported VLF results extend higher…Here’s an abstract:*
“Daytime attenuation characteristics have been computed by comparing the amplitude spectra of atmospheric waveforms recorded at four widely separated stations. The results of these attenuation measurements are presented for the band of frequencies from 3 to 30 kc/s and involving distances of 1000 to 10,000 km. Nonreciprocity is evident from this study. Attenuation rates over sea water for east-to-west propagation were about 3dB/1000 km greater for frequencies below 8 kc/s, and about 1db/1000 km greater for frequencies above 10 kc/s, than for west-to-east propagation. East-to-west attenuation rates over land were about 1 dB/ 1000km greater than for over sea water.”
Jim w5est: Thank you! On the web that leads forward to another abstract** too:
“The World Wide Lightning Location Network (WWLLN) is used to measure the normalized lightning electric field at three network stations in order to examine the sferic attenuation between the stroke and the station. The electric field measurements are normalized to the radiated very low frequency (VLF) stroke energy to allow direct comparisons of the many stroke-station paths seen by WWLLN. Comparing past theoretical results and models show that WWLLN observes a stronger dependence of VLF propagation on magnetic azimuth compared to past work. The average attenuation over the water of eastward-propagating sferics is found to be 1.13±0.35 dB/Mm during the day and 0.71±0.68 dB/Mm at night, with westward-propagating sferics having average attenuation rates of 2.98±0.68 dB/Mm and 2.66±0.39 dB/Mm for day and night, respectively.”
John XIQ (2/2/15)…In the higher latitude paths it seems that Laurence’s diode effect could be applicable. Why would a signal would “skip in” and not “skip out”. …what if several factors are at play? Like a lock and all the pins have to get hit for the door to open. What if 3 out of 4 conditions are needed for propagation to occur?
Jim w5est: Something like an ionospheric template that has absorption holes and reflective patches that need to match up with the signal ray for good propagation. Diode effect, if it exists consistently over some part of a season, would predict negative correlation between SNRs E-W vs. W-E. If diode effect lasts only a few minutes at a time, then transcripts or vignettes like the ones in yesterday’s blog can help document the diode effect.
John XIQ: Can you say more about negative correlation and diode effect?
Jim w5est: For many fall/winter nights, make a 4-quadrant chart for XKA into XCR (Yes/No) versus XKA TA (Yes/No) same night. Put counts of how many nights Yes-Yes, Yes-No, No-Yes, No-No into the chart cells. If roughly equal counts occupy all four quadrants (within statistical confidence chi-square based on number of counts), then there’s no evidence of any special effect. A physical effect would be indicated if XKA into XCR Yes/No correlated with XKA TA No/Yes respectively.
Jim w5est: Any closing remarks you’d like to give us? Thanks for your contributions!
Laurence XPQ: Just finished winding a 940mm sided square ELF loop with 925T – that keeps me busy! Cheers!
* Abstract: W. L. Taylor. (July, 1960). VLF attenuation for east-west and west-east daytime propagation using atmospherics. J. of Geophysical Research65(7): 1933–1938. http://onlinelibrary.wiley.com/doi/10.1029/JZ065i007p01933/abstract
** M. L. Hutchins, M.L., Jacobson, A.R., Holzworth, R.H., & Brundell, J.B. (9/2013). Azimuthal dependence of VLF propagation. J. of Geophysical Research: Space Physics 118(9): 5808–5812. Abstract: http://onlinelibrary.wiley.com/doi/10.1002/jgra.50533/full “
Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD gmail dot (com)!