The evening portion of this session, at least in North America, began with a strong shock wave that rocked the geomagnetic field and sent the K-index to 6. Protons were elevated in excess of 60 protons/cc, the Bz was pointing very strongly to the North, at 12+, and solar wind velocities continue above 550 km/s. DST values saw the characteristic increase before significantly decreasing:
If you have never heard a shock wave impact the GMF on the air, its pretty trippy and I highly recommend. Merv, K9FD/KH6 / WH2XCR, reports his experience to the shock wave while on 20-meters:
Even with the arrival of this strong shock wave, the band conditions in the South were very good. As I have referenced in the past, the onset on storm conditions, at least here, almost always yield interesting, sometimes very good, propagation particularly when proceeded by very quiet geomagnetic conditions. Its as if a spark ignites flammable material. It certainly breaks up the monotony of July! During this session, I decoded WI2XFI (W8RUT), which may have been the first time I received him if memory serves me. Its certainly the first time in many months at the very least.
Roger, VK4YB, reports that his noise floor is at -86 dBm and absolutely no QRN in Northwestern Australia. Roger notes, “3 nights with very low noise has resulted in no RX spots at all. People are still hearing me. Very strange.”
Ken, K5DNL / WG2XXM, reports that he decoded three WSPR stations and was decoded by twenty unique stations including sixteen decodes from WH2XCR.
Larry, W7IUV / WH2XGP, reports that he had computer problems overnight but that the situation is resolved now and he is back.
Neil, W0YSE/7 / WG2XSV, reports that he was on the air again after a few days hiatus for rig repairs. He had a good session but reports that it might have been better if he had remembered to increase the WSPR transmit percentage from 12% to 17% at bed time. Neil offers these statistics:
Phil, VE3CIQ, reports a very noisy start to the session with up to 250 static crashes per minute. The session turned out relatively typical once the noise cleared. Phil notes an interesting effect where he hears WG2XKA at sunset near -15 dB S/N but is not heard at John’s station until about one half hour later when he is also reported at -15 dB S/N. This behavior repeats on a regular basis. Phil is located West and North of John so perhaps this figures in. I have observed similar behavior with other signals moving East near sunset:
Regional and continental WSPR breakdowns follow:
There were no reports from the trans-Atlantic, trans-African, or trans-Equatorial paths. While there were no reports from this station, JV1AC, in Mongolia, appears to have been listening. At first glance it would seem that this station is bogus. There are no reports or profile on WSPRnet and QRZ does not yield any information on the station. What sets this station apart from a typical noise-generated bogus call sign is that for the call sign to show on the WSPR map without any reports (which would otherwise suggest a bogus noise generated call sign), the WSPR software would have to be reporting that the station is active. There is no way of knowing without an IP address whether the station is actually listening from Mongolia. This one bares watching in the future. It could be a prankster or an actual station.
In the Caribbean, Eden, ZF1EJ, reports WG2XXM and WG2XIQ:
Laurence, KL7L / WE2XPQ, reported VE7SL, WG2XSV, and WH2XCR overnight:
Merv, K9FD/KH6 / WH2XCR, had a nice session in spite of the active geomagnetic field and experienced two-way reports with Roger, VK4YB. David, VK2DDI, reported that earlier in the evening he had already decoded Merv 12-times. Reports were also received by John, VK2XGJ. This was another successful session:
Jim, W5EST, presents, “DIODE EFFECT, DIRECTIVE PATH: 630M GOING ACROSS EQUATOR?”:
“For clarity in the future, I’ll try to consistently use “diode effect” or “directive” regarding a radio path that’s one-way. “Reciprocal” and “reciprocity” both pertain to a distinct electric circuit and electromagnetics concept as discussed July 18, this blog.
Thanks to Roger VK4YB for this contribution:
‘Jim, Did we have diode effect on 14 July? At 11:40z everything appears normal. I am exchanging near equal SNRs with Merv. From 11:50 to 12:04z there is enhanced propagation but only in the direction of VK to KH6. By 12:14 propagation returns to normal. At the peak of the abnormality, there is a 20dB difference in path loss between the two directions.
TABLE: 630M SNR SEQUENCES, HAWAII AND QUEENSLAND, 14 JULY, 2016
Time(Z) VK4YB->XCR XCR->VK4YB XCR->VK2DDI XCR->VK2XGJ
12:12 -19 -29
11:54 -24 -26 -27
11:48 -28 -24
11:38 -15 -25 -26
I am a firm believer that radio paths are not always reciprocal, as evidenced by the TABLE. Reports you may hear, like “I called a station who was 59+ and he continued to call CQ,” are unpersuasive, however.
Possible mechanisms for diode effect: Devices do exhibit directionality, e.g. hybrid transformers, coax and waveguide directional couplers, hybrid rings, magic tees, circulators and isolators. These are linear devices and some consist of nothing more than metal tubes with holes in appropriate places.
I can imagine ducts in the ionosphere which might travel parallel to one another. There might be coupling points along the ducts. If the phase relationship between the coupling points is fortuitous, signals will enhance from one direction but cancel from the other.
A waveguide isolator is a one way, two port device. Usually it is a 3 port circulator, in which the third port is terminated and hidden inside. Powerful ferrite magnets enable Faraday rotation to occur. Port 1 circulates to port 2, and port 2 circulates to port 3, where the energy is dissipated. If a signal were to be injected in port 3, it would emerge at port 1.
Can Faraday rotation occur under the influence of the earth’s magnetic field? Learned sources say “yes”. Suppose Station A transmits in the direction of Station B. Say the direct path is not favourable. An oblique path may be open to a location where some form of rotation is operating to steer it back toward the receiving station B. When Station B replies, the path is open to the rotation area, but, alas, the rotation is in the same sense (i.e. clockwise or anticlockwise depending on the direction of the magnetic field) and so the signal is rotated away from the open path back to station A. Station B’s signal is rotated somewhere else and may be picked up by Station C or dissipated. So Station B can hear Station A, but Station A cannot hear Station B.
This is, of course, pure conjecture. Is it perhaps the sort of thing that might happen? — Roger’
Jim W5EST replying: I’d observe that XCR sunrise (SR) at 1557z is almost 4 hours later than Roger’s tabulated SNR sequence so we can rule out pre-SR enhancement.
Regarding the stations A and B scenario that Roger poses, I think it might happen, whether or not on the Queensland-Hawaii path. Let me just add a bit more to the hypothetical description. RF shoots power to lots of possible paths at once. Suppose when station B replies, the path is also open to a skew area on the opposite side of the great circle from the skew area that was mentioned. The skew overhead such an opposite geographic location can have the same sense (counterclockwise or clockwise). That way, RF signal power can get skewed/steered back toward station A. So skew might happen without amounting to a diode effect. In that case, that opposite-side return path may avoid any diode effect until something happens to path losses and degrades that opposite-side path.
An underlying question asks “How, though, do we attain some confidence our propagation description is a correct one?” In yesterday’s Alaska scenario, we’d get some confidence about skew by comparing SNRs from an omni against SNRs from a loop like Laurence did, and tabulating the SNR sequences in columns like Roger’s table today, except the respective columns of SNRs would pertain to the omni and the loop.
Roger analogized to various microwave devices and their properties. For a reference, see Pozar (2012) pages cited in the endnote.* Directional couplers are directional even when they are linear devices. Further, they are reciprocal (pp. 318, 322) unless they have ferrites, plasma, or active devices in them. So path directionality is really what we are “on about” with diode effect.
Our topic of diode effect in radio propagation primarily considers directionality, as Roger emphasizes. This is path directionality, which is a separate idea from directional antenna patterns. In our global propagation environment, GMF does of course permeate ionospheric plasma regions. We are interested in determining whether and when paths are directional on 630m.
Faraday rotation rotates the polarization of the RF signal ray component that’s propagating parallel to the GMF. Polarization is the electric field orientation in 3D that’s rotating around the direction of propagation as its axis.
Skew is a change in the direction of propagation of the signal ray such as by reflection or refraction. In reception with directional antennas, if a signal is received at a compass heading that greatly departs from great circle heading, that’s a sign of skew. Physically, I’d particularly regard a reflection as skew when there occurs a hop reflection from a non-horizontal contour surface of the ionosphere anywhere along the path.
For more, see discussion and Figure 3 halfway down in:
1999. Luetzelschwab K9LA. Skewed Paths to Europe on the Low Bands. CQ 8/1999.
I believe Carl’s article indicates there could be a “mid-latitude trough” not only on the transatlantic path but also the Pacific ocean path from WA to AK (WA-AK portion of Fig. 3.)
What about paths between Hawaii and Australia? I’ve discussed a possible F-hop somewhere around the equatorial anomaly (this blog May 14) among E-hops elsewhere. Roger seeks to describe a way whereby ducting could explain a diode effect in long-path 630m propagation. As far as I know, 630m still poses us a mystery in this area. Taking a cue from the above CQ article, consider critical frequency plots in the equatorial Pacific that give horizontal gradient information. http://www.spacew.com/www/fof2.html Critical freq fof2 contours for whole world. (It’s real time, so view it at prop time of interest.)
O/X waves can be produced by an RF signal propagating in plasma and where the RF signal ray or component propagation direction lies perpendicular to the GMF. An O-wave may reflect in a different direction than the X-wave. An ionospheric region may reflect (or not reflect) either wave, O or X, differently depending on its polarization and the angle of the GMF relative to the contours of that region, not to mention the orientation of contours of that region relative to horizontal.
The XCR-vk4yb and VK4YB-xcr paths transit low and mid latitudes where the GMF is more nearly horizontal and parallel to the direction of propagation. So Faraday rotation there is possible. GMF strength is moderate, 30-35uT at XCR and equator, rising to 50uT in Queensland. https://www.ngdc.noaa.gov/geomag/WMM/DoDWMM.shtml (click total intensity map). The gyrofrequency for equatorial sky reflections remains above 475 KHz, per the following calculation:
Gyrofrequency (KHz) = 30 uT x 28 KHz/uT = 840 KHz.
On top of all that info, we know the ionosphere contours evolve, and their ionization levels vary by time of sunset and during evening and night. Kp and Ap and ring current Dst change, and even severe GMF storms happen. SNR variations occur due to so many factors that one can also ask if a transitory instance of path directionality is merely statistical happenstance when few SNR samples occupy the sequence!
You can see why many 630m operators may prefer to improve and persistently operate their stations to develop the actual SNR information, rather than get deep into theory! As we know, some theory can help up to a point. If you didn’t know Ohm’s Law, you could waste a lot of time when you design and build circuits. Some theory-based intuition can help us assess whether various forms of propagation make sense or not. I’ll venture into Appleton-Hartree in another blog post, but with the goal of keeping it as useful and oriented to 630m operators as possible.
*Pozar, D.M. (2012) Microwave Engineering. 4th ed. NY: John Wiley & Sons. Full text on web:
318, 322 Power Dividers, Directional Couplers (reciprocal)
333 Waveguide Directional Couplers
343 Quadrature Hybrid
362-3 180° Hybrid
465-7 Faraday Rotation in Ferrite
469-471 O/X waves in Ferrite
475-6 Resonance Isolators
479-480 Field Displacement Isolators
482-3,5,6 Ferrite Phase Shifters
487 Ferrite Circulators
Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD gmail dot (com)!