Elevated solar wind velocities and an unsettled geomagnetic field don’t negatively impact lower and mid-latitude reports on the band however the dataset is limited due to an WSPRnet maintenance outage after 0700z. A number of stations provided direct email reports of their session activity, for which I am very grateful.
John, WA3ETD / WG2XKA, received the only trans-Atlantic reports for the session from DL4RAJ and DK7FC/p, which is Stefan’s elevated remote receive location in the woods outside of Heidelberg. John provided the following comments and activity map:
Roger, VK4YB, provided the following comments of his activity during the WSPRnet outage:
Berndt, VK5ABN, posted similar comments of his activity during the session:
Neil, W0YSE/7 / WG2XSV, provided the following statistics for the session based on what was uploaded by around 1400z.
Ken, K5DNL / WG2XXM, reports that he decoded five WSPR stations, including WI2XFI who is operating at 200 mW ERP and yielding -18 dB S/N in Oklahoma. Ken was decoded by 29 unique stations including SWL/K9 in Indiana at +15 dB S/N and positive S/N reports from KU4XR in Tennessee who was likely listening on the “tree-tenna”.
Mark, WA9ETW, reports a slightly better session compared to recent sessions with six unique WSPR stations decoded.
Phil, VE3CIQ, reports that he decoded WG2XKA, WI2XFI, WH2XZO, WG2XXM, and WG2XIQ during the session.
Regional and continental WSPR breakdowns follow:
There were no reports from the trans-African path. UA0SNV was present from Asiatic Russia but no reports were found in the WSPRnet database.
As previously reported, WG2XKA received the only reports on the trans-Atlantic path during the session from DL4RAJ and DK7FC/p.
Laurence, KL7L / WE2XPQ, experienced a good session with reports of Roger, VK4YB, from Alaska and Roger and Phil, VK3ELV, from Hawaii.
In Hawaii, Merv, K9FD/KH6 / WH2XCR, received reports for VK4YB, as previously reported during the outage. Merv also received reports from VK2XGJ and provided reports for VK3ELV.
Jim, W5EST, provided this viewpoint, entitled, “DISPLACEMENT CURRENT ADDS 630M ANTENNA CREATIVITY”:
“Visualizing antenna fields and displacement current can help you generate ideas for antenna geometries to analyze with antenna modeling and calculation programs. I was inspired to think about this topic by the post from Doug WH2XZO that he blogged April 10. (Any errors here are mine though.) I’ve illustrated a variation on the inverted-L antenna theme and discuss it later below.
The last few days, I’ve surveyed some fundamental ideas about MF/LF antennas. The antenna gets the RF ready to launch by putting perpendicular magnetic and electric fields in phase in a ratio E/H that somewhat matches to 377Ω impedance of free space. (This blog April 21.) “Launching RF” invites us to increase the radiation resistance and the antenna efficiency. Recall that displacement current phase is 90° from the phase of electric field E, because displacement current involves rate of change of electric field E.
Getting E and H fields in-phase therefore means positioning the antenna’s displacement current to have a significant spatial separation from the magnetic field H. That separation presages the onion-layered geometry the displacement current and the magnetic field H will need to have to regenerate each other and thereby propagate outward on their way to the sky.
A hatless, short vertical antenna launches RF to some extent. You can increase its radiation resistance by including a horizontal top hat to distribute the displacement current somewhat farther away from the magnetic field-generating vertical conductor itself. That repositioning moves the displacement current incrementally nearer the quarter-wavelength separation from the H field that it needs to have inside the radio wave after launch. (April 20, this blog.) Thinking this way brings an additional perspective to top hats, which likewise improve degree-amperes in the vertical (April 4, this blog).
Moreover, considering the antenna fields and their phasing gets us thinking about the question of what parts of the antenna are really “pulling their weight” and what parts are mostly sitting there not doing much. If USA amateurs become allowed by FCC to use MF/LF, can we recommend any more efficient TX antenna than today’s top-hatted vertical? What’s the best economy and height, least real estate footprint, and easiest construction? Have we considered many alternatives and streamlined the ones we have?
For instance, are sections of the top hat closest to the vertical antenna top point doing much to position the displacement current there in a way that launching radiation? If not, doesn’t that mean that the ends of the top hat invite us instead to pay attention to their design geometry?
Thinking about displacement current and fields brings a magnifying glass to the design of the grounding system and its radials too. Are sections of the radials closest to the vertical antenna base doing much to help launch radiation or are they shunting displacement current unnecessarily? Where indeed should most of the copper in the radials be located? If we redistribute or redesign the radial layout, can we launch more radiation than we forgo? After all, ground resistance might nevertheless worsen in an otherwise well-intentioned redesign.
What about the vertical antenna conductor itself? Generally its magnetic H field lines are nearly circular in shape as if formed on concentric cylinders, see illustration. Would we be better off running two vertical wires upward and fanning them out perhaps three yards from each other to make the magnetic H lines more flatly oval? Would that beam out RF enough better to justify the inconvenience getting two verticals up.
Today’s illustration shows one 630m antenna concept example. One well-grounded outlying conductor segment is ready to receive displacement current. A parallel central radial, likewise well grounded, parallelizes earth resistances between it and the outlying conductor segment. System ground resistance is likely substantial anyhow, so it needs to be offset by improvement in the antenna radiation resistance.
To increase radiation resistance, augment the top hat with a T-shaped end aligned overhead with the outlying conductor segment of the grounding system. This contributes a curtain of displacement current showering down vertically at some distance from the vertical antenna.
Does this antenna have directivity? If so, then plan for a desired direction of the top hat. If the antenna has increased directivity, then an amateur should be careful to stay within an applicable legal limit on EIRP. (FCC ham allocation of 630m is still pending in USA. Part 5 station licenses often allow a more generous power limit and may define it by ERP or by TRP instead of EIRP.)
Will the illustrated 630m antenna yield advantages over an ordinary inverted-L? Hopefully yes, but perhaps the more important point is that considering displacement current and antenna fields helps you deepen your antenna experience. If an antenna design doesn’t work as well as you expected, why does it underperform? If another antenna design works really well, why does it work better? This interchange of practical antenna experience with mental pictures of displacement current and antenna fields helps you build a more realistic knowledge how both antennas and fields really work in practice.
Tell us your antenna stories and tips! Let’s blog them!”
Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD <at> gmail dot (com)!