It was an very quiet start to the session with an S0 noise floor from late afternoon into the early evening at my stations. I actually checked antennas to ensure there were no problems. Signals were stronger than I expected with the G2 storm that was in progress and the East / West path dominated although a number of reports were made by stations in the North. It wasn’t quiet everywhere and Roger, VK4YB, reports the worst storms seen in 50-years in southern Australia where the entire region has lost power. He adds that his S-meter was “pinned”. It was also reported to be noisy in the southeastern US at K4LY / WH2XZO where storms persisted through the afternoon.
The geomagnetic storm has thus far peaked with a Kp of 6 although Laurence, KL7L / WE2XPQ, reported a local K-index of 8 near Anchorage yesterday afternoon. The Bz has pointed to the South during the entire session and solar wind is currently averaging 620 km/s. The Kyoto DST values suggest that, while impacted, conditions may not be as poor as the profoundly disturbed conditions reported by the Australian DST, at least not at mid and low latitudes:
Ken, K5DNL / WG2XXM, reports that he decoded eight WSPR stations including WH2XCR at 6007 km. He was decoded by 43 unique stations, including +9 dB S/N at ZF1EJ/1.
Doug, K4LY / WH2XZO, reports a noisy night where he decoded seven WSPR stations and was decoded by 27 unique stations.
Larry, W7IUV / WH2XGP, reports that he decoded eleven WSPR stations using the new eastern 800-foot long BOG and did not decode VK4YB until he switched to the western Flag receive antenna this morning. He was decoded by 36 unique stations and reports that either activity or conditions were down at his QTH:
Ward, K7PO / WH2XXP, received reports from JA1NQI-2 and JH1INM in addition to VK4YB and much of North America:
Roger, VK4YB, had the distinction of being decoded by two new countries during this session, ZL2FT and JH1NM, the later coming from the first transmission after switching the antenna to the North. Roger provided the following statistics:
“Tx 2*wh2xgp (-21) 2*va7mm (-28) 13*ve7bdq (-20) 5*wi2xjq (-24) 19*ve7sl (-20) 3*wd2xsh/20 (-24) 14*we2xpq (-21) 18*wh2xcr (-21) 1*jh1nm (-27) 28*zl2ft (-21)
Rx 2*wh2xgp (-24) 8*wh2xxp (-23) 8*wh2xcr (-17)”
Steve, VE7SL, reports “A very interesting night…hrd by 27, hrd 13. Hrd VK4YB 19 and first timer VK3ELV…hrd Merv XCR 58 times with 15 spots below -9 … also 21 spots from ZF1EJ/1 (-14 best) and two spots from Merv on his ground mounted antenna… this with K hovering between 4 and 5…Roger approached CW levels at -20 briefly.”
Steve also presented an interesting anomaly that has me wondering if it is related to our “mystery signals” seen near 1630 Hz and also generally to the West. He explains:
“John … I’m attaching a screen grab of a signal that I often see when TP condx are favorable. It often fades-up in the hour or so before local sunrise so I suspect it is towards the west.
I wonder if you might add it to the daily blog and see if anyone recognizes it or has an idea.
At first I thought it might be a digital signal but on further examination it looks like possibly an AM signal with upper and lower sidebands as there appears to be a weak central carrier at around +1810 which would make it ~476.0 KHz. Perhaps it is an NDB in Asia?”
Phil, VK3ELV, received first time reports from ZL2FT and received reports from JH3XCU from late in the previous session:
Neil, W0YSE/7 / WG2XSV, submitted the following “receive-only” WSPR and JT9 statistics from the session:
Rick, W7RNB / WI2XJQ, reports that propagation appears to be improving at his QTH, with stronger decodes for VK4YB (previously reported). He provided the following statistics for unique stations that decoded him and that he decoded:
I briefly operated JT9 during the evening hoping to catch WG2XSV’s remote access receiver shortly after sunset in Vancouver. Given the geomagnetic activity, it was expecting too much. Signals at W5EST were better than the previous session, however, and WSPR was very good for domestic paths with many CW level’s achieved. Morning CW was normal and QRN was very low. WSPR stations received at my stations can be viewed here and stations hearing my signal can be viewed here.
There were 99 WSPR stations listed on the WSPRnet activity page at 0400z. K1GTK, K5URU, and K5JM were identified as “new” receive stations. Welcome aboard!
Regional and continental WSPR breakdowns follow:
Eden, ZF1EJ, had very good success during this session, decoding VE7SL and WH2XCR on both of his receiver / antenna combinations:
Laurence, KL7L / WE2XPQ, was under aurora through this session as the G2 storm raged on. Curiously signals had less of a problem getting into the auroral zone than getting out, which Laurence refers to as the “diode effect”:
Merv, K9FD/KH6 / WH2XCR, experienced very good East / West propagation, with reports into WA3TTS in Pennsylvania and KU4XR in Tennessee. Four stations were decoded with the 80-meter dipole laying on the ground:
Jim, W5EST, presents a discussion that he shared with Joe, NU6O / WI2XJQ, entitled “PARALLEL-RESONATED MF LOOP WITH TUNING IN THE SHACK”:
“Joe NU6O WI2XBQ wrote us about his loop antenna in light of a 1942 book chapter on aircraft direction finder (ADF) loop antennas.* Joe writes:
‘Low impedance loops are used on aircraft for ADF beacon receivers where the loop must be tuned remotely. I have been using one of these since before I got on 630m. See 1st photo. Low impedance loops feature remote tuning, small size, and good performance. In my coastal environment electronics outside will not survive one good storm. It’s impossible to keep water out if it’s blown sideways several days. That was a big reason to go with the remote tuning and preamp.
The low impedance concept uses a small loop of few turns coupled by a cable to a step up transformer. The transformer serves two purposes, to match the low impedance to a FET (vacuum tube grid in the book) preamp, and to multiply the tuning capacitor reactance which is placed on the secondary side of the transformer.
The loop inductance is made about 20uH for the LF-MF band. In my case this is a two-feet-diameter shielded single turn. The text reasons that the best loop is a single turn (pp. 120,124).
The cable is important because the capacitance in a long run limits the high frequency tuning limit. Cable capacitance is the worst with 50 ohm cable, 75 ohm is better. The 110 ohm balanced variety is the lowest pF per foot I could find that is commonly available.
I am using a shielded balanced 110 ohm AES* digital audio cable, which has very low capacitance pF per foot. It also keeps everything balanced from the loop to the input of the preamp. With 50′ of cable I can tune my 2′ loop from VLF to 850Khz.
The primary of the matching transformer should have the same inductance as the loop. This worked out to 3 primary turns and 30 secondary turns on a random high-Mu core from the junk box. The secondary is 30 turns, which allows the loop to be tuned from about 300Khz to 850Khz with a 365 pF variable capacitor.
I have tried using a bigger loop, but no improvement in performance other than greater output level was noted. In fact preamp intermodulation (IM) spurs from local BC stations became an issue with the big loop.’
Jim W5EST: Please tell where the loop is mounted?
Joe WI2XBQ: My loop is mounted up on a 10′ section of tower as far away as possible from my and other houses and overhead electrical wires. See 2nd photo. Electrostatic noise is rapidly attenuated by distance from the source. On top of a house is a very poor location due to the house wiring radiating noise, which can even originate from other houses connected to the same AC power distribution transformer.
Jim W5EST comments: Joe’s e-mail and reference helpfully emphasize the importance of the matching transformer design and cable capacitance back to the shack to accomplish convenient remote tuning in the shack. The shack’s tuning capacitor parallel-resonates the circuit across a high-impedance preamp/rx input. Thanks to the wide bandwidth of his loop circuit, Joe can study and compare 630m 475 KHz long-path propagation with that of NDBs (non-directional beacons) around 300-400 KHz and broadcast station DX signals at the low-end of the broadcast band 530-850KHz.
His receiving system approach points to a loop design choice of parallel resonance vs. series resonance. In the series approach, not used there, an outdoor tuning capacitor series resonates the loop itself and steps up a resonated, mostly resistive, impedance to match a cable that matches the RX back in the shack.
In the parallel-resonant remotely tuned approach of Joe’s e-mail, the loop is radically unmatched to the cable’s characteristic impedance. But for receiving at MF that’s ok since the cable simply amounts to an equivalent cable capacitance as Joe points out. The transformer in the shack steps up the loop inductance and steps down the cable capacitance. Thanks to the parallel resonance because of the tuning capacitor in the shack, the RF signal voltage gets magnified for the very-high impedance input of the FET preamp.
The issue of preamp IM spurs: that brings up a design choice of preamp or no preamp. What’s a “best” loop design probably will differ depending on preamp or no preamp. Without a preamp, the loop may need more turns to provide sufficient signal voltage to overcome local noise and RX noise. At the same time, with no preamp, IM spurs are probably less likely since the resulting antenna circuit of all passive components is inherently linear. If the receiver system has a 50Ω input impedance, rather than very high impedance, then connect the tuning capacitor other than directly across such a 50Ω input.
Jim W5EST: Should a loop be shielded? (book, p. 119.) Since your single-turn loop is shielded, I presume the loop shield connects to the balanced cable shield.
Joe WI2XBQ: The single turn connects to the balanced cable and the loop shield to the cable shield. The gap in the shield is at the bottom. This is the design from the ARRL handbook, but it is not the best design for noise rejection, the gap should be at the top. One advantage with the bottom gap, however, is it causes a distortion in the pattern that gives a deep null one side only so a noise source can be nulled, and still receive at 180 deg.
Normally if there is a “ground” at both ends of a balanced shielded cable, only one end should be grounded. In the case of say a microphone where the source is floating above ground, both ends of the shield are connected. The loop is isolated from ground by a short piece of PVC pipe, so both ends of the shield are connected. This was the lowest noise configuration.
I do not recommend using a coaxial cable as common mode noise WILL be a problem, even with an isolated ground at the loop. CAT 6 Ethernet cable is a very good choice for this application; a shielded version is ideal. The pF per ft. is as good as the expensive digital audio cable.
By the way, for other projects, the magnetics used for Ethernet interface are fantastic isolation devices for receiving use. They are dirt cheap or free if you recycle them off old cards. They have a wide band 1:1 transformer and choke balun with a center tap to drain off common mode noise. (100Khz to 350 Mhz!)
Jim W5EST commenting: A grounded conductive shield that forms an incomplete turn can electrostatically isolate the loop by diverting stray capacitive displacement currents from local QRN sources to ground while the loop itself responds to the electromagnetic field of each remote 630m station. If the loop is mounted high up, keep the inductive reactance of the ground lead small enough to avoid floating the shield. If a shielded multiturn loop, amply space the shield from the loop turn(s) to minimize capacitive shunting high loop-end turns to low loop-end turns.
What loop antenna experiences can other readers tell us? Send us your words of wisdom!
* P.C. Sandretto. (1942). Principles of Aeronautical Radio Engineering. New York: McGraw Hill Book Co. pp. 110-127. http://www.tubebooks.org/Books/pare.pdf
** https://en.wikipedia.org/wiki/AES3 (scroll 20%)”
Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD gmail dot (com).