Autumn has arrived in the northern hemisphere but here in Texas it does not feel like it as temperatures have returned to the mid-90’s F. That means more noise from air conditioning motors and general stress on the power grid which seems to contribute to noise as ground level transformers can be heard buzzing and arcing inside their enclosures. Fortunately we cool off this weekend although the accompanying storms may complicate operating. Overnight the north central US continued to experience big storms as they migrated into the Midwest. Ken, SWL-EN61, reported from Indiana that he was using the indoor receive antennas once again and that the outdoor antennas were completely saturated with noise.
Geomagnetic conditions have returned to quiet levels with a Bz that is pointing to the North. Solar wind velocities are down from the previous session, averaging 450 km/s. DST values have smoothed and continue near nominal levels.
Trans-Atlantic propagation was split between WE2XGR/3 and WD2XSH/17. Its nice to see North American signals being reported in Europe again:
Trans-Pacific propagation was also good, most notably the higher latitude opening between Larry, W7IUV / WH2XGP, and JA1NQI-2:
Larry also reports that he decoded nine WSPR stations, excluding VK and eastern stations likely due to high noise. He was decoded by forty unique stations including a number of eastern stations, VK4YB, ZF1EJ, and the previously reported decode from JA1NQI-2:
Ken, K5DNL / WG2XXM, reports that he decoded four WSPR stations and was decoded by forty unique stations including VK4YB and KL7L:
Ward, K7PO / WH2XXP, was decoded by 45 unique stations including three VK’s. VK4YB decoded Ward at 1330z, 12 minutes after local sunrise:
Roger, VK4YB, reports the following receive statistics: “Rx: 3*WG2XXM (-23) 14*WH2XGP (-21) 42*WH2XXP (-12) 37*WH2XCR (-15)”. He adds that Laurence, KL7L / WE2XPQ, was visually identified at least six times but no decodes resulted. Roger reports the following statistics of his signal’s reception by DX: “Tx: 14*WE2EPQ (-23) 7*KL7L (-24) 2*WH2XCR (-27)”
Phil, VK3ELV, received two additional reports from JH3XCU late in the previous session:
John, VK2XGJ, reports “I started printing at 0954 z WH2XCR and WH2XXP at 1012 z with regular prints of WH2XCR, WH2XXP, and WH2XGP up until 1618 z.” Apparently there was an upload problem of some type during this session and this raw data was not processed by the WSPRnet database.
Neil, W0YSE/7 / WG2XSV, initially reported that overnight he was operating at 2% transmit cycle, focusing on reception but a follow up indicates that he was actually receive-only overnight after turning off the power supply following a CW QSO on 80m. The following reports of his signal are from prior to the CW QSO:
Rick, W7RNB / WI2XJQ, reports that he was also transmitting for a limited time but submitted the following statistics:
Several new or newer WSPR receive stations were observed during this session including N9XG, N7DTP, and WA6JBZ. Welcome aboard!
Regional and continental WSPR breakdowns follow:
There were no reports from the trans-African path.
Eden, ZF1EJ, decoded identical stations on each of his receivers during this session, including WH2XGP in Washington state and WE2XGR/3 currently located in Maine:
Laurence, KL7L / WE2XPQ, reported the well known bug when using CAT with the current alpha version of WSJTx. He transitioned from WE2XPQ/1 to WE2XPQ and used the Marconi-T for transmitting and “ACESHIGH” probe for reception with WSJTx for WSPR. KL7L was designated for receive-only, using WSJTx for JT9 and WSPR2 for WSPR with the R75 and “AMRAD/W1VD” probe. Laurence indicates heavy rain overnight:
Merv, K9FD/KH6 / WH2XCR, had a strong night with reports from JA1NQI-2, Alaska, “lower-48” and four-VK stations. VK4YB was the only VK, however, to be reported near sunrise in KH6:
Jim, W5EST, continues his thoughts about loops with “PART 3: 630M RX MAG LOOP OPTIMIZATION. TURNS?”:
“Why not endlessly wind loop turns on the largest loop diameter your QTH space allows? One prominent reason is: Turns add wire weight. More turns make your antenna more time-consuming and unwieldy to construct, and to raise and support. If you use plastic-insulated antenna wire to reduce rain and snow static, the additional turns with their insulation add still further weight.
More loop turns N in the best case do yield more induced RF antenna signal voltage at 475 KHz. However, in signal dB you reach a point of diminishing returns where the antenna is delivering sufficient signal strengths so that receiver noise is overcome and receiver gain is sufficient for reception. Best case S(dB) increases as 20log10NAf, where N is loop turns, A is loop area, and f is frequency. The incremental benefit of adding each turn is only
ΔS(dB) =20log10(1 + 1/N).
More loop turns mean more loop inductance and consequently require lower capacitances to resonate the loop. At 630m if there are too many turns, two things may happen: Air variable capacitors having small enough capacitance and sufficient low-end adjustability to resonate the antenna may not be readily available. Additionally, more loop inductance in some designs may raise the antenna Q so high that bandwidth narrows to extent that the antenna is tuning-wise unstable and difficult to adjust and maintain on-frequency in windy conditions.
Moreover, with more turns the resonating capacitance becomes less widely different from stray capacitances to the antenna from elsewhere. Electric fields of local QRN can more readily couple noisy displacement currents through such stray capacitances into the high inductance loop and even through an antenna coupling and isolation transformer.
Moreover, many loop turns introduce turn-to-turn capacitance which somewhat shunts the turns and diverts and reduces the net antenna output current responsive to a given induced RF antenna signal voltage at 475 KHz.
So, provide sufficient turn spacing to keep the capacitive reactance of each loop turn high compared to the inductive reactance per turn at the operating frequency. In my opinion, for a 630m multiturn loop, space the wire centers laterally at least five (5) wire diameters to keep the turns capacitance under control. If you have a better rule of thumb, let us know.
At higher MF frequencies the shunt reactance of the turns capacitance falls–with additional undesirable signal-shunting impact. For the various above reasons, an outdoor mag loop at higher MF generally has a single turn. At 630m, loop turns may range up to perhaps a dozen. At 2200m and other LF, still more turns may be ok, subject to diminishing returns of signal dB.
At LF and VLF, the loop inductive reactance is desirably low, while the capacitive reactance shunting the turns is desirably high and reactance of QRN stray capacitances is high with less impact. Since LF/VLF frequencies are low, the induced EMF is lower than at MF. There, more turns may sometimes be justified to acquire sufficient signal dB for the receiver.
In another blog post, let’s consider loop wire/conductor sizes and cross-sections. GL!”
Finally here is a tip for using the search feature on this website: When searching for a specific date, try the numeric format “mmddyy” where “mm” is the two digit month, “dd” is the two digit day, and “yy” is the two digit year. For example, when searching for February 1, 2016, enter “020116”. The search engine is not extremely robust so using alpha-formatted dates may or may not yield the desired results.
Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD gmail dot (com).