Post by David (N4DLT) on Aug 23, 2009 7:53:27 GMT -5
The K7RA Solar Update
The quiet Sun continues to baffle us. If there are no sunspots today -- and I don't expect any to emerge -- this will be the 42nd day in a row with no sunspots; July 10 was the last day we saw any spots. There is really no way to predict when the next sunspot will appear. If we see no sunspots through the end of the month, then nearly 80 percent of 2009 so far will have been spotless. Sunspot numbers for August 13-19 were 0, 0, 0, 0, 0, 0 and 0 with a mean of 0. The 10.7 cm flux was 67.2, 67.6, 68.1, 68.8, 68.1, 67.4 and 67.1 with a mean of 67.8. The estimated planetary A indices were 5, 4, 3, 3, 3, 4 and 10 with a mean of 4.6. The estimated mid-latitude A indices were 3, 2, 1, 0, 2, 2 and 8 with a mean of 2.6.
Unsettled to active geomagnetic conditions were predicted for August 19, with a planetary A index of 20, lowered to 15 by August 17. As seen here, the planetary A index rose to only 10 on August 19, and 11 on August 20. The current prediction from the NOAA Space Weather Prediction Center shows a predicted planetary A index of 5 for every day through the end of August. Geophysical Institute Prague also predicts quiet and stable geomagnetic conditions through the rest of the month.
The summer sporadic-E season appears over, or at least there were no reports this week. There is a shorter, less intense winter sporadic-E season, and December's ARRL 10 Meter Contest often benefits from that mode.
George Munsch, W5VPQ, who lives in Medina County just west of San Antonio, Texas (EL09ok), sent comments responding to Pat Dyer's (WA5IYX, who is about a dozen miles east of W5VPQ, in EL09ql) remarks about digital vs analog television as VHF propagation indicators. George wrote: "I have not had the pleasure of meeting Pat Dyer, but have followed his exploits on monitoring commercial signals for many years. Some early background on TV allocations may give some perspective.
"Back after WW2, Ken Bullington's 1947 Smooth Earth Models were just about all the FCC and anyone else had to use for VHF propagation predictions. Ham reports of extended propagation were dismissed, or downplayed as rare. So the initial table of VHF TV allocations was developed. After a few stations were finally constructed along the Gulf Coast, the extent of commonplace temperature inversions, and thus extended VHF propagation, became horribly evident. Florida stations were often stronger than 'local' Texas stations. So, the 'Freeze' happened: No new VHF TV licenses were issued for several years in the 1950s until a new allocations table could be worked out. Even so, interference problems continued to July 2009. I would occasionally catch UHF openings where every UHF channel (except 39) displayed a signal of some kind and VHF interference could make the low channels unusable. In the early days of (ham) VHF FM, one Saturday I listened to a new repeater being set up and mobiles going out to range check. I called in from my mobile and told them they were full quieting in San Antonio. This kind of broke up their party, as they were in Fort Walton Beach, Florida.
"Fast forward to DTV. I have a converter that scans the spectrum and records station information whenever it is 'off' (Hisense DB-2010). So far, several New Orleans stations have appeared on the list. I haven't tallied the list lately, but many of the VHF and most of the UHF channels are now represented. Houston stations are regularly seen, and often in the mornings, local stations do not manage the 15 dB margin over the distant signals and are unavailable. I thought that the locals were having transmitter problems until I fired up the spectrum analyzer. Big noise there, but the TV refuses to present a picture. Again, the FCC ignored the real world in developing the allocations table, putting too many co-channel stations in ducting range of each other. Since I have an unamplified 10 way distribution system off my antenna, I don't have quite the sensitivity that Pat does, but I still see a lot of out of area digital stations."
Thanks, George for the fascinating comments. George refers to Ken Bullington's 1947 Smooth Earth Models, an early model describing a simplified method for calculating propagation over a theoretical smooth spherical earth on frequencies above 30 MHz.
Carl Luetzelschwab, K9LA, has a new propagation column in the September issue of World Radio Online. This month's column concerns making propagation predictions for the public, and whether to assume small station or big station capabilities when making the calculations. You can download it for free to get to the table of contents -- just right-click on the four sections numbered at the left to download.
In response to the mention in last week's bulletin of the K7JA and K6CTW televised victory with Morse code over text messaging, Tom Segalstad, LA4LN, mentioned a similar demo that he and LA8AJA did for Norwegian television. You can watch the "Eksperimentet" here on a children's science program called Newton. Tom wrote: "We asked if the Morse receiver could copy the message by ear and reproduce it from memory, but that was not accepted. In that case, we could have exchanged the Morse message much faster. Next we asked if the receiving ham could type the received message into a computer, because that would also permit a faster exchange, but that was not accepted either; the message would have to be recorded by handwriting. Then we would be limited to the speed of the receiver's handwriting, which is 30 words per minute. We objected that this was not reasonable, because the receiving SMSer would not have to write down the message, but our objection was overruled."
The Morse code message was transmitted at a speed of 150 characters per minute, and was completed in 45.5 seconds. The SMS message was completed in 2 minutes. The conclusion was that the Morse code exchange won with a wide margin. The received message was controlled vs the original, and was found to be identical. "But even though the Morse code is faster, the cell phone is much smaller than the radio," says the anchor. But LA4LN replies that your use of cell phone is restricted to where you have coverage by an operator company, while Amateur Radio telegraphy has no limits -- even from a desolated island in the Pacific Ocean. "Can you flirt on Morse code?" the female SMSer asks. "Sure", LA4LN answers, "On Morse code we can transmit the code 88, which means love and kisses. 88 was chosen because it pictures the cross section of kissing lips."
I didn't know this about 88 having a graphic reference, but you can watch LA4LN explaining it with the aid of his hands, while saying something in Norwegian which sounds to me like "octo octo."
Amateur solar observer Tad Cook, K7RA, of Seattle, Washington, provides this weekly report on solar conditions and propagation. This report also is available via W1AW every Friday, and an abbreviated version appears in The ARRL Letter. Check here for a detailed explanation of the numbers used in this bulletin. An archive of past propagation bulletins can be found here. You can find monthly propagation charts between four USA regions and 12 overseas locations here. Readers may contact the author via e-mail.