No sunspots over our reporting week, December 20 – 26, so compared to the previous 7 days average daily sunspot number declined from 3.4 to 0. Average daily solar flux was 70, down slightly from 70.4. Average planetary A index increased from 4.1 to 4.3, while average mid – latitude values went from 3 to 4.

Predicted solar flux is 69 on December 28 – January 4; 72 on January 5; 70 on January 6 – 13; 69 on January 14 – 18; 71 on January 19 – 26; 72 on January 27 – February 1; 70 on February 2 – 9, and 69 on February 10.

Predicted planetary A index is 8, 12, 8, 12, and 10 on December 28 – January 1, 5 on January 2 – 4, then 10, 10, and 8 on January 5 – 7; 5 on January 8 – 12; 8 on January 13; then 5, 5, and 12 on January 14 – 16; 5 on January 17 – 19; 8 on January 20; 5 on January 21 – 23; then 8, 12, 10, and 8 on January 24 – 27; 5 on January 28 – 29; 10 and 12 on January 30 – 31; 10 on February 1 – 2; 8 on February 3, and 5 on February 4 – 10.

Geomagnetic activity forecast for the period December 28, 2018 to January 23, 2019 from F.K. Janda, OK1HH:

• Geomagnetic field will be:
• Quiet on January 10 – 12, 22 – 23
• Quiet to unsettled on January 13, 19
• Quiet to active on December 28, 31, January 1 – 2, 9, 20
• Unsettled to active on December 29, (30,) January (3 – 5,) 6 – 8, 14, 17 – 18, 21
• Active to disturbed on January (15 – 16)
• Solar wind will intensify on December 28 – 31, January 1, (3 – 4,) 5 – 7, (8, 13 – 14,) 15 – 16, (17 – 19) 

Parenthesis means lower probability of activity enhancement.

Al Brown, W1VTP, of Manchester, New Hampshire sent this email:

“I manage The Vermont Net on 3,975 kHz at 2330 UTC. We have been having propagation issues since November. I recall similar difficulties back in 2009 and it straightened out somewhere around mid Feb 2010. I have used the foF2 map put out by the Australian government for some time, but it doesn’t always make sense. I understand that Amateur Radio operators are mostly interested in DX propagation, but some of us have regional nets with average distance of 100 miles.

“Do you have any other explanation where I could predict propagation for a given night? I’m thinking it may have something to do with a disturbance in the magnetosphere and the effect of coronal dark holes when pointed at earth but do not have any reference material to back that up.

“The closest thing I have is that foF2 map but it doesn’t always work out that way.”

We covered the same issue in this bulletin in the past. This happens when sunspot numbers are too low to support local propagation on 75/80 meters. We might think of local nets in that part of the spectrum using groundwave propagation, but for wider coverage beyond line-of-sight it depends on high angle signals reflecting back from the ionosphere.

This is why NVIS antennas are useful. When I asked K9LA about this, Carl responded: “The MUF can be low enough that high angle 75/80-meter signals go thru the ionosphere at night during the winter (especially at solar minimum). As you know, with high-angle signals, the MUF is pretty close to foF2, so foF2 could be a good indicator. You may have to modify foF2 a bit based on distance. And having an ionosonde near you would be best.”

Here is a site with a number of links to ionosondes:

http://giro.uml.edu/IonogramMovies/

Note the link to Millstone Hill, which may be the closest ionosonde to W1VTP.

Click on the MHJ45 link.

Clicking on that link goes to a page with ionosonde data from 1992 to 2018.

If you click on 2018, it will take you to links for all 12 months of the year. Click on December, and click on the latest date, and you will see links for every 15 minutes of the day. I clicked on the latest one, which was for 0930 UTC at the time. It showed the foF2 value at 2.45 MHz, which is too low to support local high angle coverage for 75 meters, but 160 meters should work.

I see there are links to ionosondes at Wallops Island (Virginia), Boulder (Colorado), Eglin AFB (Florida), Idaho National Labs, and many other locations around the globe.

K9LA suggested that the net could QSY to 160 meters when this happens.

This is the ionogram I am looking at currently.

You see MHz on the X axis and timing on the Y axis. A chirp signal is swept across the HF spectrum, and the wispy looking echoes are what comes back. The various timings reveal the elevation of ionized layers. This tool should help to get a handle on this propagation problem.

From 0000 – 2359 UTC on January 1, is the annual ARRL Straight Key Night operating event.

Tamitha Skov put out this video shortly after ARLP051 was released last week, so this is a little out of date. Check here for her more recent dispatches.

For more information concerning radio propagation, see the ARRL Technical Information Service at http://arrl.org/propagation-of-rf-signals. For an explanation of numbers used in this bulletin, see http://arrl.org/the-sun-the-earth-the-ionosphere.

An archive of past propagation bulletins is at http://arrl.org/w1aw-bulletins-archive-propagation. More good information and tutorials on propagation are at http://k9la.us/.

Monthly propagation charts between four US regions and 12 overseas locations are at http://arrl.org/propagation.

Instructions for starting or ending email distribution of ARRL bulletins are at http://arrl.org/bulletins.

Sunspot numbers for December 20 through 26, 2018 were 0, 0, 0, 0, 0, 0, and 0, with a mean of 0. The 10.7-centimeter flux was 69.8, 71.1, 71, 70.2, 69.5, 69.6, and 68.7, with a mean of 70. Estimated planetary A indices were 12, 5, 3, 3, 4, 4, and 3, with a mean of 4.9. Estimated mid – latitude A indices were 9, 4, 3, 3, 3, 4, and 2, with a mean of 4.