The forecast geomagnetic storm arrived during the late afternoon in North America, upsetting magnetometers and sending K-indices and solar wind upward and Bz to the South. DST values also “tanked” on the arrival. I suspect this event will continue to rage on through the day and we will see values exceeding current highs for the event.
Even with this elevated geomagnetic activity, the band showed signs of propagation early in the evening. WD2XSH/15 was reported at my station before sunset in what was likely a storm-induced enhancement. His signals were at audible levels on a number of occasions during the period and noise levels, at least in the central US, were very quiet.
Band activity was relatively high although storms and overnight storm threats continue to plague a number of areas. John, WA3ETD / WG2XKA, reports “pop up”-type storms that manifest almost out of no where. Those type of weather patterns send me into dry dock as well.
Jeff, VE3EFF, is reported by Phil, VE3CIQ, to have improved his signal again by increasing total power out to 20-watts. Jeff’s system uses a 10-meter tall vertical with top loading that yields a full quarter wavelength. Phil notes that Jeff plans on upgrading his power to 100-watts next.
Phil, VE3CIQ, is “hanging in there” and doing pretty well from the higher latitude location that he operates from under the current geomagnetic conditions:
Neil, W0YSE/7 / WG2XSV, had a strong night from the Pacific Northwest:
Mike, WA3TTS, had a strong night of transcontinental activity from WH2XGP and has been making some comparisons after his recent lightning strike:
Larry, W7IUV / WH2XGP, reports that he decoded seven WSPR stations and was decoded by fourteen unique stations. He indicates that the band was down from yesterday which only make sense given the current geomagnetic storm conditions and his higher latitude location. He will be doing some work in the shack and may be QRT for a few days while that work is completed.
Steve, VE7SL, reports that he decoded seven WSPR stations and was decoded by ten unique stations.
Ken, K5DNL / WG2XXM, reports that he decoded three WSPR stations and was decoded by eighteen unique stations including thirty decodes from WH2XCR(6007 km) and five decodes from VA7BBG(3200 km).
Luis, EA5DOM, reports that he has installed a grabber at his station:
“Hi AllI have set a “crude” grabber for MF WSPR, MF Opera8 and LF Opera32Update is not very fast at the momentReceiver SDR Perseus with SDR Console (multi VFO) and MiniWhip antennaat IM98WX73 de LuisEA5DOM”
Drax, KB3X / WI2XJW, has been working to get his station operational using WSPR for system evaluation. He is currently using a 55-foot DX Engineering vertical that is re-purposed from 160-meters with loading and matching. He reports that he has a 400-foot beverage available for receive and has considered building a receive loop.
Eric, N6SPP, joined us again during this session from California and provided a number of reports for stations in the Pacific Northwest.
Regional and continental WSPR breakdowns follow:
There were no reports from the trans-Atlantic, trans-African, trans-Equatorial or Caribbean paths during this session.
Laurence, KL7L / WE2XPQ, operated two receivers, with KL7L using the W1VD probe and R75 and WE2XPQ operating (presumably) with the 400-foot loop. Playing host to auroral activity characterized Laurence’s session, where the K index spiked to eight:
Merv, K9FD/KH6 / WH2XCR, was decoded by my station seven minutes after local Texas sunrise today, which is something that has not happened in several months. Merv also had a number of interesting reports in Australia although a few storms off of the eastern coast may have impacted reception of his signal. Station S/N and number of decodes are steadily improving:
Jim, W5EST, presents, “PART 5 THEORY JUNGLE SAFARI: E-REGION O/X WAVE TRAJECTORIES IN 630M NIGHT”:
“The last two blog days have illustrated how the E-region inhales and exhales, so to speak, by day and by night. E-region thickness “inflates” by day and thins out by night. The plasma frequency rapidly rises with altitude inside the E-region, which corresponds to diverging refractive index values guiding the power in your 630m RF into O-waves and X-waves.
Yesterday, I illustrated how the E-region probably slants or tilts around sunrise SR and sunset SS. That slant favors the night side and can provide propagation enhancements for 630m experimenters.
Today, we will see theory predict 630m X-waves generally have longer E-hop distances than 630m O-waves. The difference narrows to the extent 630m RF travels more nearly parallel to the GMF at altitude in the E-layer overhead a geographic place where a sky reflection occurs.
Let’s take a tour of trajectories your 630m O-waves and X-waves theoretically take as they execute nighttime sky wave reflections in the E-region. Today’s illustration shows X-wave and O-wave refraction/ reflection trajectories inside the E-region.
I calculated those X/O trajectories using: 1) an estimated 10° grazing incidence angle per Note 1*, 2) a refraction law, Snell’s Law, Note 2**, 3) Chapman theory as blogged Aug. 1 to estimate plasma frequency for Appleton-Hartree (AHL) to use at each altitude, and 4) corresponding refractive indices from AHL per July 28 blog graph.
For single-hop or multihop E-layer reflection at 100 km altitude, each hop covering any hop distances in a range 1200-2200km reaches the E-layer at an incidence angle 10°-12° from the horizontal. (See “ 10° ” lower right in the illustration.) The remarkable constancy of the incidence angle (per Note 1*) is due to the curvature of the earth. Corresponding TX antenna RF launch angles range 0° to 7°, typical of most 1-Ehop and 2-Ehop 630m paths across N. America and across the Europe region. DX paths involving higher numbers of hops feature similar launch angles. Having an extensive radial field beneath a 630m vertical transmit antenna significantly augments 630m RF radiated at these low launch angles.
O-waves execute concave arcs that traverse increased vertical distance up into the E-layer, and increased horizontal distance across it, the nearer to parallel to GMF they are. (See low-lying dashed O-wave curve for GMF angle 45°.) Incident RF at 10°-12° from the plane of E-layer contours only penetrates as a grazing O-wave 2 km to 5 km into the bottom of the E-layer: about two kilometers (GMF angle 90°) to five kilometers (GMF angle 0°) penetration. Plasma frequency less than about 170 KHz is sufficient to reflect the 10°-12° incident O-wave at whatever GMF angle.
Estimated horizontal distance along which the 10°-incident 630m O-waves arc in the E-region increases from 40 km to 90 km for ray-GMF angles 90° (~E/W ray) down to 0° (~N/S ray).
630m X-waves incident at 10°-12° drill much farther up than O-waves do, about 14 km up, into the E-layer where the plasma frequency is 475 KHz. This happens regardless of orientation angle of the X-wave ray to the GMF, according to my calculations based on Appleton-Hartree (AHL).
The X-waves travel convex up to a cusp where they reflect down symmetrically and convex and exit at the same angle (e.g., 10°-12°) away and down to complete a hop. However, if the E-layer electron concentration diminishes plasma frequency below 475 KHz, then the 630m X-waves are predicted to drill through the entire E-region and ascend to the nighttime F-region where they may importantly supplement or even make possible long-path propagation on 630m.
Plasma frequency may vary in different regions of the globe. For instance, I have wondered if the equatorial Pacific region on the path between N. America and Australia might be such a place where F-region propagation is occurring on at least one hop, see this blog May 14 and its literature. E/F ducting is another possible explanation of the success 630m stations have demonstrated.
The distance that 630m X-waves travel horizontally within the E-layer varies oppositely from the way O-wave distance varies with angle between the 630m ray and the GMF. For 630m RF incident at 10°, estimated X-wave horizontal distance increases from 80 km to 130 kilometers for GMF angles 0° (~N/S ray) to 90° (~E/W ray) respectively. Each horizontal distance diminishes somewhat as the incidence angle goes to angle 12°, at which incidence angle the X-wave horizontal distance varies from 70 km to 110 kilometers.
For most ray-GMF angles, 630m X-waves have longer E-hop distances than O-waves. 630m X-waves traveling nearly parallel to the GMF feature about the same E-hop distance as the O-waves. If 630m X-waves can reach the F-region, they will far outdo the O-waves on hop distance.
Although the propagation arrows depict transmission from a TX at right over to reception at left, the propagation curves can also represent reception at right from a transmitter at left. In such case, a distant transmitter at left (not shown) sends rays at different launch angles that arrive at essentially the same angle of incidence at left but displaced from each other horizontally in the E-region as shown. Then separate arcs from the X-wave of one of those rays and from the O-wave of the other ray arrive together and combine at lower right in a receiving antenna of the TX/RX station there.
Effective height of reflection is the height of a reflection “point” as if an ascending RF ray and descending reflected ray were extended to a point of intersection inside the E-region. Per the faint dashed lines in the illustration, the effective heights of 630m O-wave and X-wave reflection differ significantly.
If you have a GMF-based propagation modeling software package that covers 630m, I’d be most interested to check these spreadsheet-calculated results against your software results. Write us at this blog to compare results, which I have checked to the best of my ability.
Keep in mind that a GMF storm will vary the pertinent gyrofrequency at E-region altitude and vary all the results somewhat. Moreover, an off-vertical tilt or a lateral skew of the E-layer can result from vertical and/or horizontal non-uniformities of electron concentration at the scale of a wavelength or more in the E-layer. That means that the actual angle of reflection can differ somewhat from the angle of incidence.
Temporary ionospheric disturbances (TID), atmospheric gravity waves (AGW), an oncoming terminator, or other dynamics may also alter either or both the angle of incidence of 630m (by tilting the E-region there) and the angle between ray and GMF. A lateral skew reflection can make the ray-GMF angle differ as between the ascending and descending parts of the ray path inside the E-region. So the calculations are just a start.
So far this theory jungle safari has explored the E-region mostly. I hope a future blog post can consider the similarities and differences of D-region behavior compared to the E-region using Appleton-Hartree to estimate losses and refractive index and consider whatever existing theory of D-region electron concentration and thickness can tell us.
*NOTE 1: HOW TO ESTIMATE RF INCIDENCE ANGLE “A” AT E-REGION
For E-hop distances 200km up to 1000 km the corresponding launch angles 45° down to 9° go inversely with distance. The corresponding E-layer incidence angles go 46° down to 13.6° w.r.t. horizontal. Paths 1200 km to 2240km have launch angles go from 7° down to 0° while the E-layer incidence angles stay nearly the same: from 12° down to 10°. Email us if you want an exact calculation procedure for any E or F hop altitude besides the assumed 100 km altitude.
**NOTE 2: O/X TRAJECTORIES FROM SNELL’S LAW
- Informed by the literature, enter an assumed value of maximum E-layer plasma frequency and its altitude (e.g., 600 KHz, 110 km). Spreadsheet Chapman’s equation (Aug. 1 this blog) in ¼ km altitude increments (or smaller) from an altitude where plasma frequency is about one-tenth (45 KHz) of operating frequency to an altitude at which plasma frequency becomes same as operating frequency (475.5KHz). I incremented from 86.25 km to 100.25 km using index values i=1 to 57. Even though the altitude increment 0.25km is less than 630m, the calculations amount to acceptable averages across the 630m wavefront at each altitude.
- Based on the plasma frequency at each altitude, spreadsheet Appleton-Hartree (AHL, July 28 this blog) to obtain the refractive index-squared n2 for the O-wave at each altitude. Do the same thing for the X-wave. Take the square root of each value to get refractive index n itself for O-wave and X-wave.
- For the lowest altitude “0” in step 1 enter your angle of incidence A’0 referenced to the vertical as computed from Note 1 above.* (e.g., 10° from horizontal is 80° from vertical).Assume 1.0 for refractive index of altitudes lower than the lowest altitude in the spreadsheet. Constrain RF ray refraction (July 27 this blog) from contour i to contour i+1 to follow Snell’s Law based on the refractive indices n in step 2 found for each altitude. For the first, lowest-altitude contour,
sin A’1 = ( 1 / n1) sin A’0
For successively higher altitudes up to the reflection altitude, repeatedly calculate refractions until sinA’i+1 reaches 1.0 or until plasma frequency reaches 475.5 KHz (e.g. 100 km), whichever happens sooner.
sin A’i+1 = ( ni / ni+1) sin A’i
- Determine each horizontal distance Δx increment traversed by the O-wave and X-wave as it rises in altitude in fixed increments, for instance Δy=0.25, according to:
Δxi+1 = Δy sin A’i+1 / sqrt(1- sin2A’i+1).
Accumulate (sum up) the horizontal distance Δx increments to obtain horizontal distance x as a function of altitude y up to the altitude at which reflection occurs. Do this for the O-wave and X-wave.
5. Line-graph the horizontal distance x as a function of altitude y to get half of each trajectory of O-wave and X-wave. Copy/paste to a slide program like PowerPoint. Copy, image-reverse, and juxtapose the O/X half- trajectory graphs each to itself in the slide program to visualize the entire trajectories of O-wave and X-wave as illustrated.”
Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD gmail dot (com)!