Due to the intensity of the current geomagnetic storm I opted to take a passive approach to this session, letting WSPR run its course. QRN was almost non-existent at my station but Doug, K4LY / WH2XZO, reported once again the presence of extremely noisy thunderstorm conditions in the southeastern US. Roger, VK4YB, also reports lingering storms off of the eastern coast of Australia. He adds that the storms that resulted in power outages in southern Australia during the previous session contained over 80000 lightning strikes according the meteorological service. He rated this session a “code 4”.
Persistent storm levels continue to impede the geomagnetic field with Kp-indices up to 6 and solar wind velocities up to 737 km/s according to Solarham. The Bz continues to point to the South and has been relatively steady. DST values are sharply negative:
Ward, K7PO / WH2XXP, was decoded by 43 WSPR stations including VK4YB and WE2XPQ, both paths that have been impacted by the recent geomagnetic storms. Ward reports that it was not a very good night:
Larry, W7IUV / WH2XGP, reported poor conditions from Washington state. He decoded nine WSPR stations and was decoded by 31 unique stations including ZF1EJ. He was listening on the eastern BOG overnight and switched to the western flag to listen for VK4YB.
Roger, VK4YB, was successfully decoded by several stations on the North side of the Equator and submits the following statistics and details for the session:
“Rx 4*wh2xxp (-23) 3*wh2xcr (-19)
Tx 1*ve7bdq (-30) 2*ve7sl (-26) 2*w6xy (-27) 3*wd2xsh/20 (-24) 1*we2xpq (-25) 22*wh2xcr (-4)”
Phil, VK3ELV, received reports from JH1INM after the reporting period during the previous session:
Ken, K5DNL / WG2XXM, reports that he decoded seven WSPR stations and was decoded by 38 unique stations including two-way reports with WH2XCR. Ken received 83 decodes from Merv with a best at 0 dB S/N at a distance of 6007 km.
Joe, NU6O / WI2XBQ, posted a couple of comments and observations on propagation this morning in the ON4KST chat/logger:
Rick, W7RNB / WI2XJQ, reports that he decoded eight WSPR stations and was decoded by seventeen unique stations:
As I mentioned at the beginning of this summary, I took a passive approach to this session, not running any CW or JT9 in the evening, relying solely on WSPR. The early evening seemed to yield the best northern reports, presumably due to a few periods of less active geomagnetic conditions. Overnight CW level reports were generally observed from stations within 1000 miles although the East / West paths also yielded two-way CW level reports, most notably, at WH2XCR during the early morning hours. My morning CW sked was normal and no other QSO’s were completed in approximately 12 minutes of CQing prior to the beginning on my sked. 160-meters was a bust this morning with no peak for E6AC or H44GC on CW. My WSPR receive reports can be viewed here and my WSPR transmit reports can be viewed here.
I did not take a census of active stations last night but judging from the WSPR map, activity was high again. N6LQB was a new receive station during this session. Welcome aboard!
Regional and continental WSPR breakdowns follow:
There were no reports from the trans-Atlantic or trans-African paths.
Eden, ZF1EJ, once again decoded WH2XCR on both of his receivers on a path that has historically very difficult:
Laurence, KL7L / WE2XPQ, continues to experience disturbed conditions and reports full-sky aurora and 28 degrees Fahrenheit. He reports a few decodes for WH2XXP early in the session. In spite of the high absorption, VK4YB and WH2XCR were decoded during the session. Laurence adds that HF is nothing but hiss at the moment:
Merv, K9FD/KH6 / WH2XCR, can hear again! He reports that he built a relay box and is now listening with his transmit antenna. He did very well, decoding a number of VK’s, including first time reports for VK7TW. Merv was also decoded by JA1NQI-2, ZF1EJ (previously reported) and stations in the East, including KU4XR and W3PM. As expected, QRN is significantly higher on the transmit antenna but signals were big so it was not a problem. Merv submitted a screen capture, shown below, of his console from near 0700z showing the 30 dB over S9 noise beginning to distort the waterfall near the edges:
Jim, W5EST, presents this discussion entitled, “PART 5: 630M RX MAG LOOP W/O HI-Z PREAMP: CONDUCTOR OPTIMIZATION”:
“Starting Sept. 19 my blog posts have discussed magnetic loop receiving antennas for 630m and LF/MF generally. Today, I summarize some modeling for conductor optimization in an antenna of the type that has an outdoor-resonated main loop, a smaller coupling loop, and no preamp.
The planned optimization: Optimize the main loop part of the RX loop using a specified conductor weight limit (this blog, Sept. 26). Subject to a given conductor weight W, I wrote a formula* for RF signal power output of a resonated nearly-circular main loop to a load that matches the metal resistance. The result favors large loop diameter, small wire size, and enough turns to constitute conductor weight W. Optimum RF signal power plateaued at the smaller wire diameters.
For the type of antenna in question, the model result makes sense because it included skin effect in the conductor metal resistance. Skin depth at 630m is about 0.10 mm in copper wire, see: https://en.wikipedia.org/wiki/Skin_effect (scroll 60% & 40%). From an RF viewpoint, only an outer 0.1 to 0.2 mm of copper wire carries almost all the RF current.
For wire diameters exceeding AWG#26 wire ~0.4 mm, the copper metal inside the RF skin is providing helpful structural support and tensile strength, but not reducing the RF resistance. https://en.wikipedia.org/wiki/American_wire_gauge . Use small wire sizes but big enough to resist wind buffeting, ice storm accumulations and hailstone hits. See two loop antennas with thin wire #20 (0.8mm) and #22 (0.64mm) at http://members.shaw.ca/ve7sl/loop.html (tic-tac-toe wood lattice, open-air 13-14 turns).
Given a largest acceptable loop diameter for your QTH and smallest physically satisfactory wire size at least as thick as AWG#26, you wind the conveniently least number of loop turns needed to easily receive 630m signals without a preamp—up to about a dozen turns on 630m with 8-foot loop diameter.
The optimization ignores loop self-capacitance which increases with the number of turns and decreases with wire diameter. However, you can independently constrain self-capacitance by spacing the turns at least about 5x the insulated conductor diameter.**
Compare today’s design-specific loop optimization with yesterday’s Sept. 28 blog of a shack-tuned outdoor one-turn loop with shack preamp. Do you have still other loop antenna experiences?
NOTES: * Main loop conductor volume N(πD)(πd2/4) equals weight W divided by metal density. Antenna voltage divided by arriving RF magnetic field H: V/H = N(πD2/4)(2πf) μ0. At 630m, that’s 2.96 N D2 v/(A/m). Conductor resistance to RF is largely skin effect for wire diameters over 4x skin depth, but is nearly DC resistance for wire diameters less than about skin depth. ρ: DC resistivity (Ω-m). N turns. D & d: loop & wire diameters. δ: skin depth =√[2ρ/(2πfμ)], ρCu=1.68×10-8 Ω-m and ρAl =1.58 ρCu. f: frequency. μ: magnetic permeability of air. Hyperbolic tangent tanh gets involved. Rmetal = [ρN(πD)/(πd2/4)][(d/4δ)/tanh(d/4δ)]. At resonance to cancel reactance and with coupling network matching the metal resistance, write power output Popt into the coupling network as half of ratio normalized voltage-squared to 2x metal resistance: Popt = (V/H)2/(4 Rmetal). Combine all the equations to get: Popt = k W D2 tanh(d/4δ) / d.
[References on request.] Conclusion: Given a conductor weight W and loop diameter D, optimum antenna power output increases to a plateau as wire diameter decreases toward zero. The wire diameter smallness is limited by physical strength considerations, not RF performance.
** Nikolova 2014, pp. 14-15, scroll 75%. Proximity effect on turns increases RF resistance and shunt capacitance. In the p. 15 graph, for spacing/diameter ratio c/b =5 it’s small.
Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD gmail dot (com).