This was a very quiet night with only a few storms in North America. WH2XZO was at CW levels during the mid-evening and Doug indicated the same but added that QRN was increasing at his QTH near bed time, impacting S/N and ruling out a CW QSO this night. WH2XCR indicated that North American signals were very strong near his sunset but his WSPR reports here were impacted due to the strong, numerous QRO signals effectively drowning his signal out. I could generally null a few loud stations using directional loops but there would always be another loud station in Merv’s direction. It felt like I was dodging LORAN on 160m! It has the potential to only get worse as we move into Winter.
Geomagnetic conditions were quiet and became quieter as the session progressed. The Bz is currently pointing to the North and solar wind velocities are averaging 380 km/s. Protons were elevated during the late afternoon in North America, peaking at moderate levels for a few reporting periods. This may be ahead of a forecast storm on the 13th that will result from a CME on Sunday. DST levels are nominal and increasing and it makes me wonder if we are about to observe a significant decrease during this session:
John, WA3ETD / WG2XKA, reports good receiving conditions but a less inspiring session than the previous:
“The first killing frost of the fall here also cooled things off at WG2XKA. Station was spotted by 24, and heard 11 uniques. Conditions were considerably flatter than Sunday night. I have been using the 35′ LNV for RX without any preamp as there is plenty of signal from that stick with a 160:8 turn ratio transformer at the LNV…noise has been very low here forthe past two sessions.”
Doug, K4LY / WH2XZO, reports good activity and conditions, decoding eleven WSPR stations and being decoded by 34 unique stations.
Neil, W0YSE/7 / WG2XSV, is back in the saddle and I feel confident that the band is a little different from the last time he was transmitting:
Ken, K5DNL / WG2XXM, reports that he was decoded by 53 unique stations including VK4YB. His session high at VE7SL was a +7 dB S/N and +1 dB S/M at WH2XCR.
Rick, W7RNB / WI2XJQ, decoded ten WSPR stations and was decoded by 23 unique stations. Rick adds, “Conditions didn’t appear to be as good as the night before at the station but I did finally get Ken in the log — so it was a good night in that respect. A bit more noise than usual may have contributed to the overall session.”:
A WSPRnet outage impacting the West, Pacific, Oceania and Asia resulted in a number of holes in data. Roger, VK4YB, reports that his first decode for WH2XXP was at 0818z and WSPRnet did not return at his station until 1056z. He issued a “Code-4” in spite of quiet noise levels and it was decided after a discussion with Steve, VE7SL, that a CW attempt was probably not going to happen today. Roger’s reports and statistics follow:
“Rx 2*wg2xxm (-28) 1*wg2xgp (-27) 16*wh2xxp (-19) 25*wh2xcr (-16) includes missing spots.
Tx 3*wh2xgp (-26) 4*ve7bdq (-26) 6*ve7sl (-24) 1*wd2xsh/20 (-23) 7*we2epq (-26) 22*wh2xcr (-2) 1*ja3tvf (-27)”
Larry, W7IUV / WH2XGP, reports that it was not a very good night due to weather, software issues and the WSPRnet outage. He was decoded by 42 unique stations “including VK4YB, VK2XGJ, ZF1EJ, and east siders.” As WH2XGP he decoded twelve, “including VK4YB on XGP RX with omni ant.” As W7IUV he decoded eleven while listening on the western receive antenna.
Ward, K7PO / WH2XXP, reports that he was decoded by 57 unique stations including three VK stations and ZL2BCG, a new reporting station for Ward:
Ken, SWL-EN61, reports “Increased level of tx activity this year … had 15 unique stations decoded overnight, a record here.”
Mike, WA3TTS, split time on 630-meters, reporting a number of western stations during this session:
“I ran a split IF from my LF/MF converter last night on the NW EWE antenna. A dozen or so captures of XCR (best at -19) as well as captures of the NW stations. VE3CNF, VE7BDQ and a single capture from the modest power WG2XSV station. Enhancement was definitely present to capture Neil’s XSV signal. Running a split IF usually results in lower SNRs so conditions must have been pretty good to XCR. Also xx captures from XND on 75 kHz which means my local noise sources were not present or were intermittent.”
Andy, RN3AGC, reports strong QRM in European Russia and requests that stations seeking reports from his WSPR stations should “use 475600-475640 and 475740-475800.” Andy, F6CNI, reports the same.
As previously reported, the band was really in good shape with very low noise levels although there were periods of significant QSB. I regret missing Merv’s reports of CW levels of my signal and feel confident that I could have found a receive configuration that would have brought his signal to usable levels for a CW QSO. Its very difficult to predict these openings and they are generally not consistent, at least based on what we know about propagation on this band right now. My WSPR transmission reports can be found here and my reception reports can be found here.
WSPR activity was once again very high. 94 WSPR stations were observed at 0230z. KB8SPI and ZL2BCG were reported to be a new receiving stations. Welcome aboard!
Regional and continental WSPR breakdowns follow:
There were no reports from the trans-Atlantic or trans-African paths.
Eden, ZF1EJ, had another big night with reports around North America in addition to two reports for WH2XCR.
Laurence, KL7L / WE2XPQ, received a lot of reports from western North America, more than I have seen in a long time and he was also hearing well, including VK4YB and WH2XCR:
Merv, K9FD/KH6 / WH2XCR, experienced another big session with large positive and single digit number S/N reports in North America in addition to reports from Japan and Australia and first time reports in New Zealand at ZL2BCG:
Jim, W5EST, presents, “PART 2: PREAMP NOISE FIGURE–BIG FICTION?”:
“Product datasheets for preamps state their noise figure F(dB). Let’s get right to today’s question: If noise factor F is simply a ratio of SNRs, and input SNR varies, how can a preamp have any one particular dB value of noise figure F(dB) and what does it mean?
The preamp independently introduces some amount of extra output noise power Npreamp of its own. With preamp power gain G included, the SNR formula works like this:
F = (S1/N1) /(S2/N2) = (S1/N1) / [(GS1)/(GN1 + Npreamp)]
Fpreamp = 1.0 + (Npreamp/G)/N1, or Fpreamp = 1.0 + Npreamp /(GN1)
The quantity (Npreamp/G)/N1 is the preamp noise referred to its input. Noise factor Fpreamp comes out the same number whether you divide that referred preamp noise (Npreamp/G) by the input noise N1 , or instead divide Npreamp by the amplified input noise N1 due to preamp gain G.
Because extra preamp noise generally increases with preamp gain, the quantity Npreamp/G is nearly a constant. But Noise factor F further depends on the input noise power N1, which has nothing to do with the properties of the preamp. So people adopt the following fiction.
For preamp data sheets, the usual practice regards that input noise level as if it were equal to the thermal noise created at the preamp’s hypothetically impedance-matched input.* Even a resistance produces electrical noise because room temperature jostles the atoms and electrons in the resistance. All of the active and passive circuit components in the preamp are making noise themselves due to sub-microscopic processes.
Consequently, noise factor F is generally some small to moderate-sized number when you measure the preamp noise referred to its input in units of the thermal noise created at the preamp’s impedance-matched input. So you do learn something about the preamp or other circuit by stating noise factor F, or noise figure F(dB), in that way; and the fiction isn’t outrageous. But that doesn’t directly or necessarily tell you how well the preamp will perform in your 630m receiving system!
To understand preamp performance on 630m, part of the puzzle means learning how 630m band noise compares with this thermal noise. How much power does thermal noise produce in a 2500 Hz bandwidth at 290°K? (WSPR SNR is referred to 2500 Hz b.w.) It turns out the answer is -140dBm.** Can I directly compare -140dBm with the 630m band noise level on a receiver that displays dBm? Yes, but you may need to do an arithmetic adjustment first. ***
Bottom line is: 630m band noise dBm can vastly exceed the thermal noise–unless you are working with a small antenna. And many 630m operators want a small antenna precisely because of the physical convenience.
A preamp may quite substantially or only negligibly improve SNR of the entire 630m receiving system while always itself slightly degrading the SNR from whatever antenna is in use. To see why a poor preamp may help at one 630m station and even a perfect preamp might not help in another 630m station, join us again for more on this topic!
ENDNOTES: *“The noise factor is defined as the ratio of the output noise power of a device to the portion thereof attributable to thermal noise in the input termination at standard noise temperature T0 (usually 290 K). The noise factor is thus the ratio of actual output noise to that which would remain if the device itself did not introduce noise, or the ratio of input SNR to output SNR. The noise figure is simply the noise factor expressed in decibels (dB).” https://en.wikipedia.org/wiki/Noise_figure 290°Kelvin is 17°C or 63°F.
** The usual thermal noise power formula is based on a thermodynamic constant k: N = TΔf k = 290°K ×2500/sec×1.38×10-23 watt-sec/°K = 10-17watts. 10-17watts = 1.0×10-14mw = -140dBm. A web site helps simplify things to -140dBm based on -174dBm (at 1 Hz b.w.) + 34dB = 10log10(2500Hz/1Hz). http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0ahUKEwjn9faF48nPAhVEeT4KHYThDvkQFggyMAM&url=http%3A%2F%2Fnoisecom.com%2F~%2Fmedia%2FNoisecom%2FWebinars%2FNoise%2520Terms%2520and%2520Applications%2520Webinar%2FNoise_Term_FINAL.ashx&usg=AFQjCNHVB52IzCV5AKXdBlaSScSGkLoSgA&bvm=bv.135258522,d.cWw
*** Example: The Winradio G33DDC SDR receiver I use shows WSPR signal peaks standing up ~25dB higher than their WSPR SNR referenced to 2500Hz b.w. would tell you. The SDR apparently is using ~8 Hz wide signal bins because noise power increases or decreases with the bandwidth, and 25dB = 10log10(2500/8).
My SDR depresses the displayed 630m noise sea relative to dBm noise level that would be measured in a 2500 Hz b.w. The narrow 6 Hz WSPR signal peaks are not pushed down because they fit in the signal bins. (Even on XSH/15 ground wave, the signal peak does vary somewhat as its instantaneous WSPR frequency shifts with the modulation.)
So when I see noise level in dBm looking like a rough sea on the spectrum display of that SDR, the thermal noise level I compare with it should be adjusted down to -165dBm (-140dBm -25dB) in 8 Hz b.w. Even when my noise canceller nulls 630m noise level down to -142 dBm as viewed in the SDR’s 8 Hz b.w., the noise power at SDR’s input is 200 times (23dB over) the thermal noise.”
Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD gmail dot (com).