It was good to be on the air all night last night without the concern of storms popping up in the local area. The threat has shifted to the East, which was a very noisy direction to listen during this session. The eastern deficit that resulted was observable on the WSPRnet report map and Phil, VE3CIQ, noted this lack of stations in his report:
Even with the complications of QRN, the band was very open on the mainland, favoring mostly shorter paths but a few transcontinental surprises were observed. Curiously, the path moving West was lacking and was very notable in the Pacific. These are interesting times on the band and its nice to have active stations that allow these seasonal observations to be made.
Geomagnetic conditions were much quieter than in the previous several sessions and the Bz continues to point significantly to the North which is likely why the elevated solar wind velocities, currently above 400 km/s, are not globally impacting propagation as one might otherwise expect. DST values are generally improved.
Wolf, DF2PY, was QRV at 472.5 kHz CW, as reported at 1854z on the RSGB “blacksheep” reflector. Wolf has been consistent about these operating times and frequencies so please look for him. He also referenced the 472 band view grabber of Stefan, DK7FC, which can be used to determine band activity. The grabber can be viewed here.
Roger, VK4YB, submitted on the ON4KST chat/logger that Graeme, VK2FPQ, reported his SSB signal at S9+ at a distance of 877 km using a crystal set! Roger reports that Graeme is using a signal generator as a BFO into a 100-foot loop antenna. I would really like to hear more specific details about Graeme’s system.
Larry, W7IUV / WH2XGP, reports that the band was, in fact, odd over night because he did not hear many stations but was heard back East, which is often a good sign that the band is open. Larry’s report corroborates my observations of depressed conditions in the West.
Mark, WA9ETW / WI2XHJ, reports that he and Steve, WD8DAS / WH2XHY, have been performing ultra-QRP tests recently using WSPR2 generated by the Ultimate-3S. Both stations have been unsuccessful thus far in decoding one another in a currently “antenna challenged” capacity (Mark’s description) over a distance of 17 miles. Fortunately these types of tests and observations breed innovation and I expect further work will yield desired results in the near future.
Neil, W0YSE/7 / WG2XSV, also notes the slump in activity and band conditions and that was when I realized this was the weekend of Dayton so we probably have a number of ‘usual suspects’ that are on the road this weekend and not on the air. Weather around the continent is not helping the situation. Neil provided the following session statistics:
During my morning CW sked at 474.5 kHz, I was testing a pair of keyed and waveform shaped GW3UEP amps (a variation on the 3rd schematic at link) combined using the W1VD zero degree combiner in the same arrangement that I use with my non-keyed GW3UEP PA’s that are driven via the MF Solutions transmit converter. At contention was how to successfully key both amps at the same time to avoid AMing and other problems that would negate the effects of the waveform shaping. A simple available DPDT relay actuated by the bug or paddle appears to yield very good simultaneous contact closures to key the amps and no spike, harmonics, or AMing has been observed. The output waveform was excellent, yielding in excess of 240-watts into 50 ohms resistive. As the 2nd amp was retrofitted with the IRF9530 keying FET and support circuit, the heat sinking is not ideal due to a lack of space in the chassis so this may need to be addressed in the long term but after a 30-minute QSO today, the situation is manageable.
Regional and continental WSPR breakdowns follow:
There were no reports from the trans-Atlantic or trans-African paths. UA0SNV and ZF1EJ were present but no reports have been found for this session.
Laurence, KL7L / WE2XPQ, reports that he was transmitting through the entire session (receive was offline, however) but failed to receive any reports. Something really bizarre must be in progress in the Northwest.
Merv, K9FD/KH6 / WH2XCR, experienced a bizarre session as well with very limited reports in spite of operating right up to sunrise. Interestingly, the very early reports received at VK2XGJ have been absent but today John is reporting Merv quite late and sporadically. Typically by this time of the session, Roger, VK4YB, gets the last word as sunrise arrives in Hawaii. Merv did share two-way reports with Roger during this session. On the mainland US, Merv reported Larry, W7IUV / WH2XGP, but failed to be heard by Larry. Some times you just have to shrug your shoulders and move on to the next session.
Jim, W5EST, presents a dialog that he and I recently had about my obsession and utilization of the GW3UEP amplifiers here at WG2XIQ in, “PART 3: CLASS E AMPLIFIER DIALOG”:
“John WG2XIQ: Class-E amps don’t have to be turned completely off or on to work efficiently. (Or avoid violent failure!) I’ve driven GW3UEP amps with sine waves with no issues and no additional heat…
Jim W5EST: RR. I’m impressed with the experience 630m folks have accumulated.* The Sokal QEX paper deep-down may tell about ‘not completely off or on’: p. 13 col. 2, p. 17 col. 3, p. 18 col. 1. Sine wave drive is mentioned at p. 18, col. 2. Would you tell about the way you do sine wave drive?
John WG2XIQ: I drive the input of the amp with about 0.5 – 1 watt sine wave. Here at WG2XIQ, two amplifiers** split drive output. I control PA drain voltage to regulate output of the final. On the GW3UEP platform, 0 dBm (1 milliwatt) drives a squarer that yields a 12v square wave at the input of the PA.***
Jim W5EST: What other features are there?
John WG2XIQ: A 2nd harmonic trap modification at L3 improves the match. The trap is a modification of L3 on Roger’s GW3UEP design, and recommended to me by XKA who encouraged more 2nd harmonic rejection. Wound with #18 enamel wire, L3 is modified to 13 uH, or about 31 turns on T106-2 toroid instead of PVC. Across the toroid and as close to the core as practical, a 2200 pF, 2.5% minimum pulse-rated cap is placed in parallel.
Jim W5EST: How would you describe the overall performance?
John WG2XIQ: I just wind them and they just work every time, centered on the middle of the band. The trap seems to clean up potential match problems as well. The amp screams power after the mod and the 2nd harmonic is basically gone. That amp makes 100W all day long into 50 ohms, and it’s capable of power beyond the nominal design–if the power supply and the output network can handle it. The FET is less efficient over 100W but works up to some failure point. I’ve seen 150W+ with a big matching network and I stopped there.
Jim W5EST: Thanks, John. I look forward to other readers sending us more amplifier experiences too!
* Sokal, N.O. WA1HQC. (2001) Class-E RF Power Amplifiers. QEX, Jan/Feb 2001:9-20.
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=12&ved=0ahUKEwjx8tP-4OHMAhVKSSYKHbw2DggQFgheMAs&url=http%3A%2F%2Fpeople.physics.anu.edu.au%2F~dxt103%2F160m%2Fclass_E_amp_design.pdf&usg=AFQjCNEVu5gz7gsdmT5xwWtIpd8hbGx0rw including cites to Sokals’ 1975 patent and their 1975 IEEE article; and F. Raab (1977):
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0ahUKEwiU2Muys-TMAhUK7yYKHYGMCLkQFggvMAI&url=http%3A%2F%2Fwww.asudokuaday.com%2Fbloggy%2Ffiles%2Fidealizedoperationoftheclasse.pdf&usg=AFQjCNE2_M8OSwtt5PpbskhAtr7TLyxBCA and further citations in this blog May 18.
***http://www.gw3uep.ukfsn.org/100W_QTX/100WTX/PA_cmos.gif (472-479KHz. 2011.)
Compare with these two web pages:
http://www.gw3uep.ukfsn.org/100W_QTX/100WTX/100WTX_2july11.htm (Alternative keying ckt for PA, photo, scope waveforms and auxiliary test oscillator circuit.)
http://www.wireless.org.uk/qtx.htm (See construction photo based on different 2009 schematic.)”
Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD <at> gmail dot (com)!