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More trans-Atlantic reports from DK7FC at WD2XSH/17; Higher latitude eastern path begins to open again; Geomagnetic field starting to show signs of new activity; W5EST zooms in on the T/R and QSK question

– Posted in: 630 Meter Daily Reports, 630 Meters

Quiet terrestrial weather and slightly active geomagnetic conditions resulted in a very good session here at my station in Texas with many very good and persistent signal levels observed.  Judging by the WSPR decode counts alone on transmit and receive, I would guess that at my latitude, the band is back to where it was (where it should be for this time of year) prior to the most recent geomagnetic storm.  A low latitude auroral warning has been active over the previous several sessions but that does not seem to be seriously impacting signals at my latitude.  I suspect, however, that due to the level of geomagnetic activity currently experienced, which may be giving signals here enough “spark” to propagate effectively, higher latitudes may be hampered some.  Of course the path to KL7 and trans-Atlantic openings have been more common so the higher latitude paths are not completely compromised.  Not yet anyway.

I do wonder if those storms off of the US Atlantic coast created problems for eastern US stations.  There were plenty of reports from that area overnight.

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11-hour North American lightning summary

 

John, VK2XGJ, reports that the QRN from storms in eastern Australia is abating just a bit but remaining at S7 – 8 as evening progressed.

Geomagnetic conditions have been quiet but elevated.  Elevated proton numbers were observed through much of the session and at some point overnight the Bz pushed significantly to the South.  Solar wind velocities continue to average near 370 km/s and DST values have rebounded from yesterday’s downward trend.  Solarham is reporting that we should expect storm conditions again on Nov 12, just in time for the special event.  Hopefully the timing will be such that the onset will bring us propagation advantages rather than total absorption.

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Trans-Atlantic reports were back but not as robust as the previous session, as WD2XSH/17 received DK7FC.  The report details for this opening can be viewed here.

Toby, VE7CNF, reported that he was running CW during the late evening, likely as a shake down for this weekend’s special event:  “MW CW beacon is on 476.5 kHz until 0700, 30 sec between repeats.”  At 0635z he reported that he was going to QSY to 477.5 kHz.  He returned to WSPR at 0732z, indicating very good reports with +7 dB S/N at VE6JY.

Ken, K5DNL / WG2XXM, reports that he was decoded by 49 unique stations with 85 decodes from WH2XCR and eight from WE2XPQ.

Joe, NU6O / WI2XBQ, reported an average session with nothing unusual aside from a report from WH2XCR one hour and fifteen numbers after local sunrise in northern California.

Rick, W7RNB / WI2XJQ, reports that he decoded twelve WSPR stations, two were bogus, and he was decoded by 24 unique stations.  Rick’s unique station detail summary can be viewed here.

John, WA3ETD / WG2XKA, experienced transcontinental openings at higher latitudes again.  John adds:

“A much improved session to report – the PNW opened nicely and most of the usual suspects appeared.  Noise was nominal for the season.  XKA ran considerably less power than usual due to popup rain showers and wind – thus it seems conditions were pretty good.”
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WG2XKA session WSPR activity

Neil, W0YSE/7 / WG2XSV, reports that his signal is pushing East again.  He explains:

“I was able to penetrate that RF wall to the east this session. VE4XC decoded me 9 times with a best of -21. Also Laurence(of AK) decoded me 11 times with a best of -10, and ur XIQ heard me 3 times (best of -23), and Merv, XCR, got me 24 times (best -9).”

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WG2XSV session WSPR activity

 

The trans-Pacific path’s from North America were complicated during this session and difficult to characterize (aside from calling them poor).  As John, VK2XGJ, reported earlier in this summary, noise is decreasing on the East coast of Australia but it continues to be very noisy.  That said, perhaps its not unimaginable that even WH2XXP and WH2XND are not decoded by one of the stations that seem to hear well down under.  What is curious is that WH2XGP, who hears very well in spite of living in an RF “twlight zone”, did not hear Roger, VK4YB, but Roger was reported by VE7SL.  Steve doesn’t have a clear path to VK from his location.  So there are a lot of things going on here and its probably impossible to put all of the elements in a single box – its not a black or white solution.  Steve adds that his reports of Roger occurred at the same time as the JA stations were reporting Roger so this may be a simple case of the antenna being directed to Asia rather than North America.  I am really amazed that the pattern could be that tight, however.

With all of that in mind, Roger, VK4YB, was received by JA3TVF, JE1JDL (two-stations reporting under the same call sign), and VE7SL.  Roger had no reception reports as I review the data this morning so either QRN continues to be very high, propagation is more mysterious than normal, or Roger muted his audio input on his PC.  The report details for the two JA’s and VE7SL can be viewed here.

I received a nice note from Daniele, I55387FI, an SWL located in Italy who takes a great interest in 630-meters and reports that while a small antenna is currently in use, there are plans for much a much larger antenna system in the future.  Its so nice to hear about non-hams that take an interest in radio.  In the recent months I have received a large number of non-ham SWL reports and appreciate every one of them.  It makes what seems some days like endless CQing more palatable.  Esoteric radio is alive and well.

Ron, WA4JNX, sent a note about a couple of receive antennas options on the market that work into the MW range:

“If any of the guys are interested here is some current info on a couple of LW “one and only” antennas:  First is the PK Loop.Currently $103.70 delivered by airmail from Melbourne and worth every cent:  http://amradioantennas.com/longwave_antennas.htm

Next is the RadioPlus Q-Stick, $69.50 delivered by Priority Mail from Pensacola: http://dxtools.com/QStick.htm

I have both and they work well with any portable with an internal ferrite bar ant. and LW coverage.  Both Paul and Gerry are good guys to do business with,too.  You get about 10% more gain by using them together,BTW. (inductive co-coupling effect) 73…ron WA4JNX”

I returned to CW during the evening part of the session, beginning prior to sunset and operating until full dark before transitioning to WSPR.  I started earlier than I planned on yesterday but due to the time change I am still trying to work the kinks out of the schedule.  I suspect I will be QRV by 2300z or 2315z tonight.  This morning’s CW was normal, complete with a CW sked at 1130z with WG2XIQ/1.  I CQ’ed until sunrise and QRT’ed at 1255z.  As previously reported, WSPR suggests that the band was very good.  I am sorry that I did not take better advantage in the late evening.  The time change and early wake ups have created havoc as I struggle to adjust.  Maybe some JT9 or CW in the late evening is in order tonight or tomorrow night.  It was also nice to make it to WE2XPQ, a path that has become rare.  My WSPR transmission reports can be viewed here and my WSPR reception reports can be viewed here.

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WG2XIQ 24-hour WSPR activity

 

I didn’t make a late count of WSPR stations but near local sunset there were 90 MF WSPR stations reported on the WSPRnet activity page which is notoriously low in its reporting numbers.  I can only guess that the number increased as the night progressed.  AJ8S returned for this session, hearing very well.  This may be his first reports this season.  Welcome aboard.Regional and continental WSPR breakdowns follow:

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North American 24-hour WSPR activity

 

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South American 24-hour WSPR activity

 

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European 24-hour WSPR activity

 

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African 24-hour WSPR activity

 

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Central / Asiatic Russian 24-hour WSPR activity

 

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Japanese 24-hour WSPR activity

 

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Australian / New Zealand 24-hour WSPR activity

 

Eden, ZF1EJ, is stringing together a few very consistent nights, with continued reports from New England and the Pacific Northwest.  I suppose I should be expecting more KH6 reports any day now:

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ZF1EJ 24-hour WSPR activity

 

Laurence, KL7L / WE2XPQ, indicates that he has been impacted by something overnight as European utility stations on 137 kHz has disappeared.  Whatever happened, it seems that the path to KH6 and VK4 was open, perhaps only slightly diminished from yesterday, and in addition to receiving numerous reports from stations in the Pacific Northwest, he provided reports from me and WG2XXM.  Laurence’s VK and KH6 report details can be viewed here.

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WE2XPQ 24-hour WSPR activity

Merv, K9FD/KH6 / WH2XCR, provided fourteen decodes to VK4YB and received a single decode from JH3XCU during this session.  It was a weird, uncharacteristic night for Merv.  He had a good night into mainland North America, however, with reports into VE4 and south central US.  Merv’s JA and VK report details can be viewed here.

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WH2XCR 24-hour WSPR activity

 

Jim, W5EST, presents, “PUTTING A MILLISECOND MICROSCOPE ON 630M T/R AND QSK”:

“Today I dig deeper into yesterday’s blog dialog about T/R relaying and the question of full power 630m QSK.

Regarding vacuum relay harmonics and radiating up and down a band, it was assumed that the relay is mistimed so that it cuts out a tiny fraction of a second before CW transmit power is truly off. The sudden power-off transition would cause a very hard key click that has a lot of wideband or spurious frequency content.

I think the most basic question at hand is whether 630/2200m CW QSK at full power is important enough in the first place to justify your efforts to achieve it.   For short to medium distance ragchewing andtraffic handling, try for QSK– I think there’s a lot to recommend it. Moreover, low-power 630m QSK, while not totally simple, is within many ops’ capability.

For long path work, I think a station without QSK could “surf” 630m QSB by transmitting for 5-10 seconds and listening for 5-10 seconds and capture most long path QSB fade-up wave-swell opportunities for QSOs.

That said, amateurs and experimenters are nevertheless a hearty and hardy bunch of MF/LF mountain climbers, and full power 630m CW QSK is an interesting and challenging mountain!  So let’s dig deeper into QSK with a “millisecond microscope.”

How long does it take for CW transmit power to turn truly off at a 630m transmit station? Here goes my take. If you have better wisdom, let us know.

The CW transmitter itself may have shaping circuitry to “soften” off-on-off transitions and minimize key clicks. For instance if an on-off transition takes up a fraction k ~ 1/10, one-tenth of a dit-length or space, how much is that in milliseconds?  Back of envelope, I’d guesstimate about 6 milliseconds at 20 wpm. (See endnote.*) Since the CW transmitter would be applying power during those 6 milliseconds, one could only do relaying and transitioning to RX sometime after that power had ceased.  Even at lower WPM, you’d probably still want that 6 ms amount of transition time.

Besides keying waveform shaping inside the CW transmitter, the TX antenna system involves an RLC network including the antenna tuning unit ATU, vertical antenna inductance and capacitance, and antenna resistance and grounding system resistance.  That RLC network has a quality factor Q that tells us the ratio of amount of RF energy in the system divided by the energy dissipation in each cycle.

Unlike HF, a 630/2200m TX antenna system has much higher Q than an HF antenna. When the transmitter turns off, a 630/2200m TX antenna system “rings” with RF energy for a significant length of time. How long is that?  I estimate for purposes here that a typical 630m TX antenna rings for roughly 2 ms.** Trying to turn on the receiving system during this time would risk a lot of extraneous QSK popping noises in the receiver. That means you probably need about 8 ms (i.e., 6ms + 2 ms) on 630m not only to get the TX transitioned off but also to get the antenna system energy dissipated.

At this point, T/R circuitry should start detuning the TX antenna, begin undetuning the RX antenna, and commence exposing any preamplifier and the receiver itself to the RX antenna.  All those operations can ideally be performed timewise in parallel or nearly so. Suppose that process takes perhaps another 10ms, which is probably over-optimistically brief,  but remember I’m looking for a theoretical low amount.

From the instant a dah or dit ceases, it evidently hypothetically takes 18ms (i.e., 6 + 2 + 10ms) to get T/R accomplished on 630m.  Presumably one’s ear subsequently needs significant time to auditorily sense whether another station is present, which probably takes at least roughly 40 ms. Then to get the next dit or dah started will take still another 18 ms of T/R time reversing all the steps. I’m guessing about 76 ms (i.e., 18+40+18ms) is needed for the CW spaces if a 630m station is doing full-power QSK, full break-in.

Bottom line: I deduce an upper WPM limit for 630m CW full-power QSK to be about 15 wpm.***  This result suggests that 630m CW full-power QSK up to 15 wpm is not impossible, even though it may be difficult to achieve.

On 2200 m the T/R delays would exceed those on 630 m, due to longer-duration of antenna ringing, so I’m guesstimating 10 WPM 2200m CW full power QSK is probably the maximum achievable QSK code speed on that LF band.

Please do not rely on these guesstimations if you are putting your own TX/RX station design on the line with 630m or 2200m QSK.  Do your own calculations and test with measurements at greatly reduced power first. Compare your wisdom with the most relevantly experienced operators you know.

What do your experience and knowledge tell you?  E-mail us so we can blog the best wisdom!”

*Note 1: I worked from a click bandwidth guesstimate in Hertz  Δf ~ 1/(kΔtdit).  Substitute k~0.1 and  Δtdit (sec) ~ 1.2/WPM to get Δf ~ WPM/0.12  Then at 20 wpm, the dits (and spaces) would be 60 milliseconds in duration, and soft clicks~170 Hz wide.  Suppose on-off transitions 6 ms (1/10 of 60ms).   http://www.rfcafe.com/references/qst/why-key-clicks-october-1966-qst.htm (scroll 40%).  http://www.eham.net/ehamforum/smf/index.php?topic=8534.0;wap2 ; and https://en.wikipedia.org/wiki/Morse_code (scroll halfway).
** Note 2:  Δtring (ms) ~ (Q/2πfKHz) 0.23(TPO dBm – RX acceptable dBm). With antenna/ground system Q ~ 100 at 475KHz, I estimate for example 200 watts TPO (53 dBm TX power output) and guesstimate acceptable RX dBm at -110 dBm by the time the TX antenna ringing decays.  
      Δtring  ~ 1.2 ms = (100/2π 475) 0.23(53 + 110), which I round up to 2ms.
The above formulas are based on a conversion from dBm to power and use an energy dissipation-per-radian definition of Q:  https://en.wikipedia.org/wiki/Q_factor (scroll 25%).  See also: http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0ahUKEwiCgfbR5JnQAhXJYyYKHSfVBBEQFggiMAE&url=http%3A%2F%2Fwww.ece.ucsb.edu%2FFaculty%2Frodwell%2FClasses%2Fece218b%2Fnotes%2FResonators.pdf&usg=AFQjCNGUfO4C3CIDEmsFBwdTKTIn2lBySg Based on Q, I write a declining energy equation  [1- (2π/Q)]N = [100.1 (- 110dBm) ] / TPO. Cautiously, the equation imagines the full TPO dBm of the undetuned TX antenna must dissipate to -110dBm before undetuning the RX antenna that’s in the near field. The equation left side closely tracks an exponential function (e-x) , so I convert the right side to exponential form by using 0.23. Solve for N, the number of RF ringing cycles needed to dissipate TPO RF from the TX antenna system down to RX acceptable dBm. Period (ms) of one RF cycle is 1/fKHz. Apply Δtring = N x (1/fKHz) to finally get the formula I stated first.
*** Note 3: If Δtdit (sec) ~ 1.2/WPM, then WPM ~ 1200ms / Δtdit(ms) = 1200ms/76ms = 16 wpm, which I round down to 15 wpm.

 


Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD gmail dot (com).