Truthfully it was a big night just about everywhere. Reports had a high variability over the entire session, but there were plenty of big signals to go around. The activity in the Pacific is a big deal because the path between Japan and Alaska and Australia and Alaska have only been observed recently and much of that is afforded to active stations, whether they be transmitting, receiving or both. It pays to listen!
The trans-Atlantic path cannot be neglected as its large-scale appearance has been rare recently. The path from DK7FC to WG2XPJ in Vermont yielded six reports, with one or two reports each going to WE2XGR, WE2XGR/3 and WG2XKA. John, WA3ETD / WG2XKA, noted that the noise level was extremely low through the session. Perhaps this is key to all of these reports.
The geomagnetic field was generally quiet after a period of instability yesterday and the Bz was slightly south-pointing with solar wind below 400 km/s.
John, WA3ETD / WG2XKA, also noted the following:
John also noted the presence of VE3OT’s ‘MP’ QRSS beacon on 475 kHz again after successful cross band QSO’s during the activity weekend. John provided the following screen capture:
Neil, W0YSE/7 / WG2XSV, noted that he would be operating a JT9 beacon on 474.2 kHz + 1200 Hz until at least 0500z and provided the following report this morning:
Toby, VE7CNF, noted in the ON4KST chat/logger that he was hearing Neil’s JT9 at -6 dB S/N at 1026z.
WSPR activity was actually down compared to the previous session where only 71 MF WSPR stations were reported on the WSPRnet activity page as of 0150z. Its possible and likely that the number was significantly higher but after a long day I did not stay up late to take another census. KE3PL returned for the session after a hiatus, as did Roger, ZF1RC, joining us again after being away for a few weeks. We were also joined by W6WGF and AE2EA, neither of which have I observed in the past upon inspection of the operator roster. Steve, W6SJP/BY, and UA0SNV, were also in attendance during the session but no WSPR reports were recorded in the database.
Regional and continental WSPR breakdowns follow:
There were no reports from the trans-African path.
Roger, ZF1RC, returned after being away for a few weeks and joined Eden, ZF1EJ, to provide reports from the Caribbean.
DK7FC was the golden boy on the trans-Atlantic path, with reports from WG2XKA, WG2XPJ, WE2XGR, and WE2XGR/3.
Laurence, KL7L / WE2XPQ, won the triple crown over night, receiving reports from JE1JDL, JH1INM, and JH3XCU on a path that has largely been non-existent at best and uncharacterised in terms of data gathering at the very least. Laurence also had reports from WH2XCR as well as West Coast and Pacific Northwest stations. KL7L was designated for receive-only.
Not to be outdone, Merv, K9FD/KH6 / WH2XCR, put on a show of his own, with reports from JA1NQI-2, JH3XCU, VK2XGJ, WE2XPQ, KL7L and reports for Phil, Vk3ELV.
Additionally, Phil, VK3ELV, was reported by JH3XCU and JH1INM, with some reports late in the previous session.
Laurence, KL7L / WE2XPQ, provided this updated additional information about Phil’s station from an email correspondence with him following yesterday’s very long trans-Pacific opening:
Additional anecdotes, comments, information and statistics:
Joeseph, NU6O / WI2XBQ, reports that he sent pictures of the burned Delrin insulator to DX Engineering, the supplier of the 43-foot vertical that he uses and they were “horrified”. Joe is working on a solution to get back on the air and indicates that he has plans to experiment with alternative loading methods shortly.
Jim, W5EST, continues his thoughts on antenna matching, SWR and how both are impacted by a change in frequency:
630M TX FREQUENCY CHANGE: RE-MATCHING TX ANTENNA & SWR
Mismatch means reflected power. Reflected power heats up your TX power amplifier and steals watts from your MF/LF TX antenna system, not good. How much reflected power does a change to a 630m frequency off-resonance produce? The result+ comes out as: Prefl =PTPO / [(R/( L Δω))2 +1] =PTPO (Q Δω/ω)2/[1+(Q Δω/ω)2].
Suppose you’re feeding 150 watts to the example Q=100 antenna and change frequency just 1 kHz or +/-0.21%. Estimated reflected power is 6.3 watts. Change the frequency +/-2 kHz or 0.42% reflects back 22.4 watts. And +/-3 kHz means 42.8 watts reflected. It’s worth readjusting the match to the 630m antenna system.
What happens to SWR when changing 630m frequency 1 KHz or more? See the accompanying graph. First of all, I’m assuming that the antenna coupler transforms the antenna system resistance, e.g. 30Ω at resonant frequency. There’s an impedance ratio (like 5:3) to get to the feedline characteristic impedance (50Ω). When you move to a frequency off resonance, and prior to any readjustment of the antenna coupler, that coupler transforms R + jX by approximately that same impedance ratio.
The off-resonance antenna reactance X = 2LΔω, say 12.6Ω at +/-1 kHz from resonance. On the way to SWR, use any of the three quantities X/(2R) = LΔω/R = Q Δω/ω = e.g. 0.21 at +/-1 kHz. The SWR is then written out in terms of any those three equivalent expressions. For instance, in terms of antenna Q, SWR for fractional % frequency departures is approximately++ this:
SWR ~ 1 + 3 Q |Δω| /ω .
The SWR in the Q=100 antenna turns out to be about 1.5 : 1 at +/-1 kHz from antenna resonant frequency. |Δω| means absolute value of frequency departure, always a positive number. You can see that the higher the antenna Q, the faster the SWR goes up.
Now let’s get a bit clearer what we mean by SWR on 630m. The usual picture of SWR has a transmission line of substantial electrical length, wherein you divide maximum RF voltage somewhere on the line by the minimum RF voltage somewhere else. Actual variation in RF voltage depends on the electrical length of the line and the ratio of antenna system impedance to transmission line characteristic impedance (say, 50Ω).
If you feed a 630m TX vertical with 50Ω coax from a shack 40m (130 feet) away on an acreage, that’s about 1/16 the wavelength or about 1/8 turn around a Smith chart (perhaps somewhat more, depending on the coax velocity factor). Many of us may have shorter coax runs on considerably less real estate than that. So the characteristic impedance Z0=50Ω of the coax might be less important than 630m antenna system resistance R as a reference. But that’s only when you ignore the transmitter itself.
You could hypothetically deliver the 30Ω antenna resonant system resistance directly to the shack via a short run of 50Ω coax. There you could provide a TX matching network (shack antenna tuner) to match the 50Ω TX power amplifier to about 30Ω and tune out whatever Smith chart reactance the coax run introduced. If you go to a frequency off resonance in that hypothetical 30Ω system, then the SWR relative to 30Ω is what today’s graph will tell you. But if you put a 50Ω SWR meter on the coax itself, it will say the SWR is 1.67 (=50Ω /30Ω) even though the match to the hypothetical 30Ω antenna system would be perfect. Ditto for scope match+++ circuitry built for 50Ω.
So be very sure your TX power amplifier in fact either sees 50Ω or is not being forced beyond its design limits if you confront the TX power amplifier unit with something besides 50Ω. Moreover, consider how an automatic tuner and/or SWR fault detector will operate if it thinks 50Ω means a perfect match and you decide on something else.
Does your real experience call for corrections or comments to yesterday’s or today’s post? By all means, let us know. We truly value your experience, knowledge and sound common sense!
+RF voltage reflection coefficient K = (Z-R)/(Z+R), where Z = R+jX. R is antenna system resistance as reference.
Since power is proportional to square of voltage, Reflected Power/ PTPO is |K|2, (squared magnitude of K).
So: K = (R+jX – R) / (R+jX + R) = j2LΔω / (2R + j2LΔω) = 1/[(R/ jLΔω)+1].
Then |K|2 = 1/[(R/ LΔω)2+1]. We saw LΔω/R = Q Δω/ω, which leads also to |K|2 = 1/[1 + 1/(Q Δω/ω)2 ].
++If you want the full SWR formula, just e-mail me at firstname.lastname@example.org for it.
+++ See scope match article http://myweb.tiscali.co.uk/wgtaylor/LFTA.pdf by Jim Moritz M0BMU.
Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD <at> gmail dot (com)!