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The K7RA Solar Update


Average daily sunspot number dropped from 24 during the previous seven days, to 5.6 in the current reporting week, February 15-21. That average is so low because no sunspots have been seen since February 17, and no new sunspot regions were observed since February 4. Average daily solar flux dropped to 70.1 in the current period from 77.4 in the previous week.


Based on the latest 45-day prediction for solar flux, I expect sunspots to re-appear by March 2 or 3, when solar flux is expected to increase suddenly.


Predicted solar flux is 68 on February 23 to March 1, 69 on March 2, 76 on March 3-12, 74 on March 13-14, 72 on March 15, 70 on March 16-25, 72 and 74 on March 26-27, and 76 on March 28 through April 8.


Predicted planetary A index is 8 on February 23-25, then 12, 16 and 8 on February 26-28, 5 on March 1-3, 8 on March 4, 5 on March 5-13, then 10, 8, 12, 16, 14 and 12 on March 14-19, 8 on March 20-22, 5 on March 23-30, 8 on March 31 and 5 on April 1-8.



Greg Andracke, TI7/W2BEE, wrote from Costa Rica, where he is vacationing: "Now on the air with a 124.5-foot sloper antenna. I am working CW only when not in the pool! I will be in Playa Garza, Guanacaste, Costa Rica until about March 15. If anyone needs a CW contact, e-mail me at: I'm not running pileups; just chatting with folks. Made only a few contacts during ARRL International DX contest because I couldn't get antenna installed until about 3 hours before the competition was over.”

Greg has a fascinating career filming documentaries. See


A new space weather video from Dr. Tamitha Skov last week:



Paul Gray, N0JAA, of Melbourne, Florida wrote: “Late winter/early spring is generally the time of year in Florida when we typically experience tropospheric ducting. his year is no exception. I have experienced a good amount of ducting on 2-meters so far. I don't have sideband capability on that band currently, so my experience is limited to FM repeaters and simplex. On 2 meters through 70 centimeters, tropospheric ducting in Florida occurs mostly in the late evening and overnight hours. The 6-meter band, at least in my experience, does not appear to be significantly affected by tropospheric ducting. 


“Over the last week or so, I have been receiving a distant repeater on my club's repeater frequency of 146.610 MHz (W4MLB) in Melbourne. I have been able to receive and, after a fashion, carry on contacts with, several stations on the K4GSO repeater. The trick is to let each repeater drop before responding, but it can be done. Considering that 2 meters is basically line of sight, plus or minus a few miles beyond the horizon, and the distance between Melbourne and Ocala is approximately 150 miles, this is a good feat, especially with a 5-W handheld transceiver and a 1/2-wave mag-mount antenna! I would consider this DX on 2 meters.”




Geomagnetic activity forecast for the period February 23 to March 20, 2018 by F.K. Janda, OK1HH.


“Geomagnetic field will be:

Quiet on February 25-26, March 1, 6, 10, 12-13, 19-20,

Mostly quiet on February 27, March 2, 7, 11,

Quiet to unsettled on February 23-24, March 3, 5, 8, 15-16,

Quiet to active on February 28, March 4, 9, 17-18,

Active to disturbed on March 14.


Amplifications of the solar wind from coronal holes cannot be predicted for the period until March 10, but I do not expect any significant upsurge. Then solar wind will intensify on March 18-20.



- Parenthesis means lower probability of activity enhancement.

- With regard to ongoing changes, current forecasts remain less reliable, especially in the first half of March.”



Tomas Hood, NW7US, who edits the Propagation column in CQ was interviewed by Eric Guth, 4Z1UG, for Eric’s podcast QSO Today:


If you change the end of the URL from nw7us to k7ra, you’ll hear me being interviewed about two years ago.

For more information concerning radio propagation, see the ARRL Technical Information Service at For an explanation of numbers used in this bulletin, see


An archive of past propagation bulletins is at More good information and tutorials on propagation are at


Monthly propagation charts between four USA regions and twelve overseas locations are at


Instructions for starting or ending email distribution of ARRL bulletins are at


Sunspot numbers for February 15-21, 2018 were 15, 12, 12, 0, 0, 0, and 0, with a mean of 5.6. 10.7 cm flux was 72.5, 71.5, 69, 70.3, 69.1, 70.5, and 67.6, with a mean of 70.1. Estimated planetary A indices were 11, 7, 12, 14, 17, 5, and 4, with a mean of 10. Estimated mid-latitude A indices were 6, 7, 10, 14, 11, 3, and 3, with a mean of 7.7.