[South Florida DX Association] ARLP005 Propagation de K7RA

[Bill Marx]

SB PROP ARL ARLP005
> ARLP005 Propagation de K7RA
> 
> Solar activity is very low. Average daily sunspot numbers for the
> week were down over 40 points to 9.1. Average daily solar flux
> dropped nearly 11 points to 80.6. Geomagnetic conditions, with the
> exception of January 26 were stable and quiet. On January 26 the
> interplanetary magnetic field, which can shield the earth from solar
> wind if it is pointing north, turned south, and the mid-latitudes
> experienced some moderate geomagnetic activity, with the A index for
> the day at 15. Polar regions saw a lot more activity, with the
> College A index in Alaska going to 36.
> 
> Currently the sun is spotless since January 29. Daily readings of
> zero sunspots could continue for another week. We will observe more
> and longer periods such as this as we head toward the solar minimum,
> still expected about to occur about a year from now. Geomagnetic
> conditions should remain quiet, and solar flux around 77. This may
> not begin to rise again until February 10.
> 
> January is over, so let us examine the average daily solar flux and
> sunspot numbers for the month compared with previous months.
> 
> The average daily sunspot numbers for the months January 2005
> through January 2006 were 52, 45.4, 41, 41.5, 65.4, 59.8, 68.7,
> 65.6, 39.2, 13, 32.2, 62.6 and 26.7. Average daily solar flux for
> the same months was 102.3, 97.2, 89.9, 85.9, 99.5, 93.7, 96.5, 92.4,
> 91.9, 76.6, 86.3, 90.8 and 86.6.
> 
> As expected, the solar cycle is declining, but there is a lot of
> variation from month to month.
> 
> Richard Buckner, who wrote the ACE-HF and ACE-HF Pro System
> Simulation and Visualization Software for propagation prediction
> mentioned in response to last week's bulletin that ACE-HF can do 160
> meter predictions, but with some limitations. He sent along a quote
> from the ACE-HF Basis for Predictions tutorial, written by George
> Lane:
> 
> "160-m Prediction Accuracy. 160-m frequencies are rounded to 2.0 MHz
> to conform to VOACAP's lower frequency limit. VOACAP 2-MHz
> predictions are reasonably accurate for NVIS and short-range
> predictions out to about 1500 km. But when path distances are very
> long, VOACAP becomes less accurate at night. At night, a residual
> E-layer exists with a MUF usually above 2 MHz. It is this phenomenon
> that permits AM broadcasts in the medium-wave bands to propagate
> thousands of kilometers during nighttime hours. VOACAP, however, is
> based on data that was collected at frequencies of 4 MHz and higher.
> Extrapolation was used to cover the lower frequencies, but funding
> limitations prevented the collection of further data to support
> those extrapolations. Unfortunately, computed absorption values are
> excessive in the extrapolations and the nighttime predictions thus
> become excessively attenuated as path distance increases. For this
> reason, 160-m nighttime predictions at long path distances should be
> used with caution."
> 
> You can find more information on ACE-HF at,
> http://home.att.net/~acehf/.
> 
> We heard again from Charles Lewis, S9SS of Sao Tome (an island off
> the West African coast, west of Gabon). On January 20 he wrote,
> 
> "I made 150 - 160M contacts last week. 51 were in North America,
> coast to coast. It was, as usual, very slow, tedious going. E-mails
> to me cited large pileups. As usual, I heard no pileup. Usually, I
> hear only one, occasionally two, stations cresting my high level
> noise. Even most "big gun" stations only get through when their
> signal is enhanced greatly by whatever propagation phenomenon. Even
> "little guns" find themselves all alone in the spotlight on my stage
> now and then, despite all the better equipped callers. There is no
> such thing as cracking the pileup on me on 160 meters since I never
> hear it."
> 
> Charles continues, "In the Stew Perry, I heard only five NA stations
> in close to three hours of listening and worked all five easily. It
> was interesting that I heard one station on and off for nearly two
> hours, while I heard the others only briefly for one period."
> 
> He goes on to say, "An interesting quirk here is a rogue LU 10 meter
> beacon that I hear often on the IARU beacon frequency for hours at a
> time when the band is so dead that I hear none of the IARU beacons.
> Weird!! I favor the W3VD beacon when I am specifically looking for
> an opening to the USA on 10M since, unlike 4U1UN, it transmits
> continuously on 10 M."
> 
> He continues, "I used to experience the antipodes enhancement
> phenomenon on the upper bands often when I was A22AA in 89-92. I
> would often work Hawaiian hams (and hear WWVH) when the bands were
> nearly in a blackout condition."
> 
> If you would like to make a comment or have a tip for our readers,
> email the author at, k7ra at arrl.net.
> 
> For more information concerning radio propagation and an explanation
> of the numbers used in this bulletin see the ARRL Technical
> Information Service propagation page at,
> http://www.arrl.org/tis/info/propagation.html. An archive of past
> propagation bulletins is found at, http://www.arrl.org/w1aw/prop/.
> 
> Sunspot numbers for January 26 through February 1 were 24, 29, 11,
> 0, 0, 0 and 0 with a mean of 9.1. 10.7 cm flux was 86.9, 83.5, 80,
> 79.5, 78.8, 77.6, and 77.6, with a mean of 80.6. Estimated planetary
> A indices were 29, 8, 6, 3, 1, 2 and 4 with a mean of 7.6. Estimated
> mid-latitude A indices were 15, 7, 4, 1, 0, 1 and 3, with a mean of
> 4.4.
> NNNN
> /EX
> 
>