This session was just “OK” with really nothing to write home about. The band was open but the distances covered really depended on the ability of the receiving station to discriminate storm noise, which was more wide spread than in previous session. This session was representative of Spring/Summer band conditions. The reality is that the conditions should stabilize some once Summer arrives and high pressures settles in. Until then, sit back and enjoy the bumpy ride and don’t forget to unplug the coax as storms approach.
Geomagnetic conditions were quiet. The Bz has been pointing to the North and the solar wind velocity averaged 330 km/s through the session, in the low range. The Kyoto DST report was unavailable this morning but the Australian DST suggests otherwise “normal” conditions.
Phil, VE3CIQ, had a bit of excitement when he first looked at the WSPR map for his activity overnight when he saw a report from the Pacific ocean. Unfortunately it turned out to be a phantom. Phil reports otherwise local signal. During the evening Phil observed a thumping noise at 474 kHz from his switching power supplies which impacted his ability to use his E-probe and likely compromised his ability to hear WH2XGP on the transcontinental path if open. Phil’s cure was to add a 1K resistor across the supply output “to raise the charge pump cycle” a bit. The noise is now gone when listening on the E-Probe. That’s a valuable technique for anyone plagued with some types of noise. Phil’s session map is shown below:
Neil, W0YSE/7 / WG2XSV, provided these comments on his session activity:
Regional and continental WSPR breakdowns follow:
In the Caribbean, Eden, ZF1EJ, reported WH2XZO in South Carolina:
Laurence, KL7L / WE2XPQ, reports that his area experienced multiple wide spread power outages during the session due to an accident involving power poles. Subsequently this impacted life in many ways during the evening and overnight, in spite of generator and battery power. He was successfully decoded by WH2XGP while power was available and he reported this morning that power returned at 0818z:
Merv, K9FD/KH6 / WH2XCR, in Hawaii was QRT during this session.
Jim, W5EST, provides the following discussion entitled, “PART 4: COMBINING TX VERTICAL AND SHORTER RX VERTICAL”:
“Using EZNEC Demo I modeled a 50’ tall 1.5” dia. TX vertical overtopped with 2×100’ #12 (0.0833” dia. uninsulated) hat wires slanting to 30’. A 20’ tall 0.5” dia. RX vertical had 2×25’ hat wires slanting to 10’. (4 segments each vertical, 3 segments each hat wire. Copper loss included.) Real/High Accuracy ground.
50mS/m “Real, High Accuracy” ground represents a radial system shared by both antennas for low-angle long path work. Because of the lower height of the RX antenna, the Source Amplitude is 11x multiplied in the model specification. The vertical TX and RX antennas are only 50’ apart, so the real estate footprint is favorable.
By trial and error, I set the phase of the small antenna to 190° and obtained a unidirectional pattern. This way I attempt to employ a modeling program to simulate the action of a noise canceller with a taller vertical and shorter vertical connected to its inputs.
The solid angle A at 3dB down is A ~= (40° x 132° cos(40°/2))/57.32 = 1.51 steradians. Beamwidth Figure of Merit is 2π/1.51~= 4.2. That’s a considerable improvement in noise rejection capability compared to 1.3 for a vertical. Compared to a vertical alone, the beam is lowered from about 50° to 40° so that high angle regional storm static rejection improves. The unidirectional feature also improves rejection of band noise N off the back and sides. Moreover, using the TX antenna’s radial system to underlie the RX vertical provides good low angle reception of signal S down to about 1° elevation. In this way, SNR = S/N improves.
Murphy’s Law guarantees these advantages are exaggerated compared to the results you will obtain with a real system. First of all, a vertical is high-impedance in the sense that local noise can readily couple via stray capacitances into the antenna system. However, as noted in the blog May 24, several operators are obtaining good results from some vertical antenna constructions. One needs to have each vertical in this noise cancelling duo working well by itself before there’s much hope of improvement cancelling them in tandem. See the literature links for various phaser noise cancelling arrangements including one similar to the modeled system.*
Ground wave noise from the outlying locality will arrive at this noise cancelling antenna duo as well. However, such noise would have arrived at a single vertical antenna constructed over a good ground/radial system anyway. Also, it’s possible that a unidirectional loop would achieve similar RX results and be no more difficult to construct at some distance from the TX vertical.
The demands on phasing and possibly-needed preamplification will also introduce departures from the calculated results. Nevertheless, the exercise of studying and computing a cancellation pattern for this antenna duo is a helpful step toward a deeper understanding of possibilities and pitfalls in the band-noise cancellation field on 630m.
Have you tried some noise cancelling system or have related wisdom for us to blog? Do you have “shootout” results involving an RX loop competing with other MF/LF antennas? We look forward to your stories!
*Dallas Lankford. (2012) Tests Of New Active MW Antennas.
Dallas Lankford. (2008, 2011). Small Amplified Vertical Antenna.
See some Dallas Lankford passive phasers:
Antennas and active circuits with a commercial noise canceller: See manual p. 20, 21, 22, 27, 28. Pages 19-20 show short RX vertical phased against a taller TX vertical.
Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD gmail dot (com)!