The band continues to produce results, for better or worse, as the days get longer and the noise level increases. My station was at least able to remain in receive-only mode overnight after a hopeful beginning to the evening was crushed by the trains rain showers that tend to update the system impedance when unsupervised for several hours at a time. The morning CW sked was scrubbed at 1015z because of an approaching lightning-rich line of storms. Tomorrow may be better but I tend to be a bit optimistic.
Geomagnetic conditions have been elevated but quiet although G1 storm levels are expected within the next 24-48 hours. The Bz continues to point to the North which may be providing some relief from the elevated solar wind velocities which persist above 400 km/s in the moderate category.
John, WA3ETD / WG2XKA, was testing at QRP levels overnight with good results and presents these details:
Phil, VE3CIQ, reports consistency over the previous sessions and notes the value of good antennas, citing the performance of the QRP activity at WG2XKA:
Neil, W0YSE/7 / WG2XSV, indicates that the band has been favoring specific directions over recent session and provides these statistics:
Wolf, DF2PY, reports that he was CQing on 472.5 kHz CW at 1839z. No details of any QSO’s generated from this operating session but European stations should listen for him during the evenings as he has been active.
Dick, W7WKR / WD2XSH/26, reported to the 600-meter research group email list that he is on the air again after some station improvements and provides additional evidence of the importance of a quality radial system:
Regional and continental WSPR breakdowns follow:
There were no reports from the trans-African or trans-Atlantic paths. UA0SNV and ZF1EJ were present during the session but no reports were indicated.
Laurence, KL7L / WE2XPQ, reported yesterday that his QTH is already not seeing full darkness, as the greyline is now at Nautical and Astronomical twilight. Laurence was reported by WH2XCR (two-way reports) and was decoded by VE7BDQ and WH2XGP.
Merv, K9FD/KH6 / WH2XCR, received reports from two stations in Australia, two stations on the US mainland and WE2XPQ in Alaska. Its been an interesting couple of weeks for Pacific signals and I appreciate Merv’s diligence in activity.
Jim, W5EST, presents additional comments on yesterday’s topic in “PART 2: CLASS D AMPLIFIERS FOR MF/LF”:
“PWM and 10x switching as discussed under the heading for Class D on May 18, this blog, are seen in audio amplifiers, but not familiar on ham/experimental MF/LF.*
Today let’s look at an example MF/LF Class D pulse amplifier. See its MF/LF push-pull amplifier schematic (13.8vdc, 100w) at http://www.g0mrf.com/classd.htm . **
An input flip-flop circuit responds to input at twice (2X) the output frequency to generate staggered non-overlapping pulses that ultimately drive push-pull PA FETs. The action resembles two people alternately pushing a child’s playground swing (LPF) from each end of its travel to reach desired height (power output) in the presence of friction (the antenna load).
To eliminate harmonics, the antenna system load receives amplifier’s RF power via an LPF L1-L2, C1-C3 or another suitable LPF design. The MF/LF Class D amplifier delivers two pulses of energy to the LPF per RF cycle instead of Class C’s one per cycle.
Tell us your experiences with amplifiers at MF/LF. TU & GL!
*Thanks to John WG2XKA WA3ETD for encouragement on today’s topic. Any errors are mine.
**Also, see http://www.w1vd.com/137-500-KWTX.html (Scroll 30%, click for its schematic, LPF is outboard, not shown.)”
Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD <at> gmail dot (com)!