Good trans-Atlantic openings existed as F5WK made a good impression with many stations in the northeastern US. Band conditions suffered here as it was a stormy evening and early morning at my station. Doug, K4LY / WH2XZO, reported very noisy conditions at sunset in South Carolina and I suspect that noise was high across the South and many areas around North America. Good propagation was reported in the West and the trans-Pacific path was once again active in spite of very high noise in Oceania.
Geomagnetic conditions ranged from quiet to unsettled to storm levels during the session. A geoeffective coronal hole is expected in the coming days which should result in the return of persistent storm conditions. The Bz has been pointing to the South for much of the session and solar wind velocities have returned to moderate levels, averaging 430 km/s. DST values have shown expected decreases:
The trans-Atlantic path was kind to F5WK who was reported by WD2XSH/17, W1TAG, WA3TTS, and two-way reports were shared with WG2XKA, who indicates that this is his first reception report in Europe this season:
WD2XSH/17 also reported PA3ABK/2 on a number of cycles during the early evening:
Ward, WH2XXP / K7PO, was decoded by 48 unique stations overnight including VK4YB and VK2XGJ. North America was very well represented also:
Roger, VK4YB, reports a very noisy night in Queensland with even the normally very strong stations not being reported over the last two hours of his operation, resulting in a “Code 4”. A major highlight for Roger was the first time report of VK4YB at WG2XSV, who was using a new receive arrangement consisting of an E-probe without a noise-cancelling system. He indicates that he will be using this arrangement for the next three weeks but with these results it may be longer. WI2XBQ also reported two-way decodes after increasing the height of his receive loop. He adds that propagation was good in all directions. Roger provided the following statistics:
“Rx 3*wh2xgp (-24) 5*wh2xxp (-22) 1*wi2xbq (-29) 7*wh2xcr (-22)
Tx 12*wh2xgp (-18) 1*va7mm (-29) 2+wi2xjq (-24) 1*wg2xsv (-27) 5*wd2xsh/20 (-21) 1*wi2xbq (-26) 11*we2xpq (-24)”
Larry, W7IUV / WH2XGP, reports that he decoded nine WSPR stations and was decoded by 43 unique stations in a session with “decent activity and so-so conditions”. Larry shared two-way reports with VK4YB:
Phil, VK3ELV, had reports from late in the previous session from JH3XCU:
Neil, W0YSE/7 / WG2XSV, had a nice surprise this morning with reception reports of VK4YB. He provided the following statistics and comments:
I was totally blown away this morning when I read on the chat site that I had decoded Roger, VK4YB. And that was on the E-probe antenna !
Yesterday I had switched out the 630m system so that I could TX and RX with the vertical on 160 meters so I was not TX-ing on 630 last night.
Rick, W7RNB / WI2XJQ, reported that he “…was heard by WA3TTS and K3SIW/1 in PA. and IL plus several others in the Midwest and Canada. Yeah! And VK4YB was in here again — !!!!”:
Mike, WA3TTS, requests that stations carefully check their transmitting frequency to ensure that they are not co-located with other stations, particularly DX stations. This can be complicated as the activity page shows an average of reported decode frequencies rather than the frequency that stations believe that they are actually transmitting on. If a receive station is not careful or has a “loose” receiver, they could blow the reported frequency by several MHz. Furthermore the active page is not extremely reliable with updates. One solution is for transmit stations to run lower transmit percentages which often negates co-location problems. There is no simple solution to this problem aside from everyone carefully watching where they are putting their signals. Mike provided the following statistics on the session from his station:
John, VK2XGJ, reports that he “…just printed WH2XCR on the system that is not set to report. I’m running two system in parallel using the Kenwood R5000 and the Icom R8500 and as I thought the R5000 would be best it was reporting. So I have now switched reporting to the R8500. First 630 m print today by the R8500 was at –28 dB 0910 z.”
Garry, K3SIW, posted the following comments on LOWFER:
“Interesting WSPR signals overnight on 474.2 kHz. WH2XGP at times was very strong as local sunrise neared (up to -5 dB SNR) and not surprisingly a couple of stations seldom decoded came through (WI2XBQ and WI2XJQ)”
Ken, SWL/EN61, in Indiana reported on the ON4KST chat/logger that he was decoding VE3CIQ at -6 dB S/N in spite of storm QRN.
Regional and continental WSPR breakdowns follow:
There were no reports from the trans-African path.
Eden, ZF1EJ, had an identical session to the previous as QRN conditions have not improved much:
Laurence, KL7L / WE2XPQ, had good coverage along the West coast of North America and reports of VK4YB who QRT’ed early due to high noise from local storms:
Merv, K9FD/KH6 / WH2XCR, reported that decodes began at sunset in KH6 resulting in good coverage along with West coast of North America in addition to Manitoba and East to Ontario. As with others operators, the path to VK was crippled by strong QRN in Australia:
Jim, W5EST, presents “PART 4A: 630M RX MAG LOOP OPTIMIZATION STRATEGY RE CONDUCTOR SIZE”:
“With a given diameter and number of main loop turns, the metallic resistance to RF and the overall weight of the main loop conductor turns are established by the conductor size. I’m ignoring an inner coupling loop for now, if any.
Is there a best wire or tubing size for the main loop? Should the conductor be copper or aluminum? Which is better: metal tubing or wire at larger wire sizes? Would PVC holding the loop wire be a better choice? Even if PVC or metal tubing is more likely to be able to support its own shape, is that enough to make either PVC or tubing preferable?
You could take issue with the premise of this post—that you should optimize an RX loop at all. Perhaps optimizing a loop isn’t critical. How about a reputedly-noisy band like 630m? Can’t you simply get rid of local QRN and receive the band noise well above the RX noise level, and beyond that no improvement in SNR is possible?
Since a goal here is to gain some design-pertinent insight into how a receiving loop works, let’s suspend judgment and see what conclusions emerge. The purpose of an antenna is to deliver reception performance, so I first consider how to convert the most arriving radio wave signal power into power for the receiver from the antenna.
A radio wave carries only a finite amount of signal power for the antenna to convert into electrical RF voltage and current. The more you load an antenna down the more current flows in it, which itself makes a magnetic field that increasingly cancels the magnetic field of the arriving radio wave. This partially self-defeating antenna action on the receiving end is another way of saying your RX loop has radiation resistance.*
OK, fine, so just couple a 50Ω receiver to match the loop radiation resistance Rrad itself, right? Maybe on HF you could, but it doesn’t work that way at 630m MF. For practical 630m magnetic loops a few meters in diameter like ones you can hope to rotate, the metal resistance** including skin effect is almost always far greater than radiation resistance* by a factor of hundreds to thousands of times. See TABLE and endnotes tomorrow.
If the metal resistance is inescapable, let’s match to that. Efficiently matching a 50Ω receiver to a loop with metal resistance of, say 1Ω to 3Ω (1000-3000 mΩ) is possible for some 630m multiturn wire loop designs in that range. But for other loop designs the metal resistance is far less—down to 100mΩ (0.1Ω) and even less. For those, your RF coupling transformer or network will almost certainly introduce large or considerable losses in the matching process, relatively speaking. In every case, we will perforce throw away almost all the arriving signal power!
If we can’t do better, can we at least do small RX loops less atrociously? If not, let’s see why not. Let’s try to penetrate this topic deeper and see what we learn.
Physically and economically we MF/LF experimenters just can’t increase the loop antenna conductor diameter and loop turns and antenna area indefinitely in hopes of matching the radiation resistance itself. Consequently, I rule out an optimization strategy based on such matching. So my plan for another blog post is: Optimize the main loop part of the RX loop using a specified conductor weight limit. Conductor weight physically loads down whatever support structure you use. Conductor weight and shape are related some way to wind loading too.
You may see a better optimization strategy or way to proceed—if so, please e-mail so we can blog it. Tomorrow’s Part 4B will blog the TABLE and endnotes. After that, I plan to work through the weight-limited optimization strategy by way of example.”
Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD gmail dot (com).