This is the most excitement we have had in a few weeks. For starters, John, W1TAG / WE2XGR/3, in Maine provided decodes of Stefan, DK7FC, on the trans-Atlantic path:
Also notable was the appearance of 3B8IK on Mauritius. While this station was reporting the wrong frequency, near 685 kHz, I am hopeful that he will return and have a reasonable chance of decoding European stations much like FR5ZX did earlier this season.
This morning I observed extremely quiet conditions while preparing for my morning CW sked. The lightning map was essentially clear which was a significant difference from the evening portion of the session where lightning was spread from coast to coast.
Geomagnetic activity was elevated to unsettled levels ahead of forecast storm levels. The Kp-index was elevated for much of the session and Bz was variable from North to South. Periods of solar wind with velocities above 500 km/s were also observed, subsiding to an average of 485 km/s while this report is being assembled.
Phil, VE3CIQ, reported a noisy session with transcontinental propagation:
Neil, W0YSE/7 / WG2XSV, had a much better session, including reports to the East where David, WB0VAK,in Minnesota showed just how well a station at a quiet location can hear under otherwise noisy conditions:
In addition to David, there were and have been several very faithful stations listening from Minnesota, Wisconsin and the Daktokas and those reports and activity are very much appreciated.
Regional and continental WSPR breakdowns follow:
There were no trans-Pacific or trans-African reports during this session. UA0SNV was present during the session but no reports have been submitted.
In the Caribbean, Eden, ZF1EJ, reported WH2XZO and WG2XIQ:
Laurence, KL7L / WE2XPQ, continues to operate in receive-only capacity while decoding WG2XSV and WH2XGP:
Merv, K9FD/KH6 / WH2XCR, was QRT for this session as he hosts guests on the island.
Jim, W5EST, presents the following discussion on noise management entitled, “LOCAL NOISE CANCELLATION”:
“It’s a jungle out there,” and you live nearby! PCs, TVs, wall warts, light bulbs, fluorescent lights, motors, AC power lines, cable TV coax, DSL, etc. Imagine each such local noise source reaching out with tendrils of displacement current to grow noise and reduce SNR in your LF/MF antenna system as illustrated here.
Suppose a tall vertical antenna A1 is the receiving antenna. Local noise often originates at points in the near field region. The near field region almost entirely features reactances and works like an extended circuit. Accordingly, the schematic illustration shows a hypothetical capacitor network circuit model where stray capacitances variously couple one or more sources of local noise into the system A1 and noise antenna A2.
After local-noise cancellation in a noise canceller, best-case SNR approximates:
SNR = (S-kS) / (Nband + Nlocal – Nlocal).
The improvement in dB is roughly
Improvement = 10log10 [(1-k) (1+ Nlocal /Nband)].
Some signal power kS may unfortunately cancel, as represented by factor k. If local noise power Nlocal is large compared to band noise power Nband, noise cancellation of local noise power Nlocal can dramatically improve SNR without reducing signal power S very much. In a pathologically noisy location you might see 20dB or more SNR improvement this way on 630m!
If you do noise canceling, and your canceler arrangement yields more than 5-10dB SNR improvement, it’s probably canceling local noise, not band noise. Even if your canceller were set to a phase that could cancel band noise, the amplitude setting that cancels local noise will probably diverge markedly from amplitude scaling that would cancel band noise.
Noise canceling of local noise, as displayed on a spectrum analyzer when you adjust the canceler dials, looks like draining a bathtub and seeing kids’ bathtub toys emerge! Remember the canceler settings then may have almost nothing to do with the ones that would cancel band noise. Using a noise canceller to fight serious local noise may deliver adequate SNR performance in your region or even your continent but probably not transoceanic DX path-conquering performance.
Radiation resistance and corresponding signal S reception capability of each antenna A1 and A2 is proportional to the square of its respective height h1 and h2. By contrast, capacitance of each antenna increases directly with its height and amount of top hat and closeness to noise sources. So a small noise antenna A2 picks up mostly local noise, which is readily cancelled by a canceller circuit. Also, you can more flexibly situate a small noise antenna closer to a local noise source to attain more noise pickup into noise antenna A2 than the main antenna A1 suffers relative to that local noise source.
The versions of local noise received by antennas A1 and A2 can only be cancelled if they are correlated—scaled versions of each other, for which phasing and scaling can bring them into cancellable antiphase. If either antenna fails to pick up a local noise source, that source will be uncorrelated and not cancelled. If the noise antenna A2 picks up a local noise source that does not reach the main antenna A1, then that noise will be undesirably included in the canceler output.
Multiple sources may inject different local noises into antennas A1 and A2. Each local noise source N1, N2, N3 induces a noise voltage N11, N21, N31 in antenna A1 and another noise voltage N12, N22, N32 in antenna A2. That means antenna-specific sets of noise voltage ratios may differ, so N11: N21: N31 is different from N12: N22: N32.
In that case, each noise pair N11, N12; N21, N22; and N31, N32 in the noise canceller is still probably a correlated noise pair. Nevertheless, the noise pairs can’t all be fully cancelled with any one noise canceller setting because a setting that cancels one noise pair doesn’t fully cancel another noise pair.
It should be possible to manipulate the canceller dials to increase SNR somewhat, though. If the improvement is inadequate, relocating the noise antenna A2 by trial and error may better align its aggregated local noise pickup with the constellation of local noises being coupled into the main antenna A1. Understanding that the ratios of noises need to align can give you some intuition where a good noise antenna A2 location may be found.
Highly-linear signal antenna and noise canceller preamplifiers beneficially employ active devices such FETs and/or other active devices in circuits at the antenna or elsewhere. Residual nonlinearities may multiply out-of-band QRM signals together and produce mixing products that have frequencies equal to the sum and difference of the original frequencies of each pair of QRM signals (and/or noises) that become multiplied together.
Since broadcast band stations offer many different arithmetical possibilities involving BCB strong carriers and modulation frequencies lying 475KHz apart, active antennas with such preamps require careful design. Some noise cancellers add an adjustable BCB trap. MF/LF ops and SWLs appreciate all-passive well-matched antenna and noise canceller circuits for their inherently high linearity. But the lack of signal power gain calls for careful design in the all-passive arena too.
While noise cancellation of local noise may not be a perfect solution, it can be quite useful on 630m when implemented after all other noise reduction measures have been taken. We look forward to learning your experiences and results. GL!”
Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD gmail dot (com)!