Report

Space weather: solar flux 105, 10 below its 90-day average of 115. Maximum usable frequency 13 megahertz, measured by the Idaho Falls ionosonde via KC2G: long-distance paths open through 30 meters, 20 meters and up closed. Critical frequency 4.1 megahertz, so 80 meters is good for NVIS. K index 3, active. No significant flares. Data from NOAA.

Coronal holes become more common as the cycle declines, bringing geomagnetic activity that repeats about every 27 days, one solar rotation. If conditions are disturbed today, watch for a repeat in about four weeks.

Sun and moon, Pacific Daylight Time: sunrise 7:07 AM, sunset 6:50 PM, day length 11 hours 43 minutes. Moonset 2:56 PM at 304 degrees, west northwest. No moonrise today. Last quarter moon, 42 percent lit. The Orionid meteor shower peaks Wednesday, October 21, a meteor scatter opportunity on 6 and 2 meters. Moonbounce: the moon peaks tomorrow at 8:07 AM, 76 degrees high and 3 percent closer than average, a good time to listen for EME signals on 2 meters and up.

VHF and UHF tropospheric enhancement is often strongest from sunset to early morning, when a nighttime temperature inversion forms.

Amateur satellite passes for the next four hours. No passes above 30 degrees in the next four hours. Frequencies and live status at amsat.org/status. Pass predictions at n2yo.com.

Satellite tip: image satellites are receive-only. An FM receiver and a phone app such as Robot 36 can decode their pictures; set the app to the satellite's mode, or let it detect the mode automatically.

DX activity, via the cluster network and hamqsl.com. None spotted by West Coast stations right now. No aurora or 6 meter E-skip.

Tropospheric ducting, from balloon soundings 7 hours ago: No ducting strong enough for amateur VHF or UHF bands over Oakland. K6EEG's experimental tropo forecast, based on NOAA atmospheric model data, for the next 12 hours. Bay Area coast, peaking around 11 AM: ducting likely on 70 centimeters, 75 percent; a chance of ducting on 2 meters, 30 percent. Southern California coast: a chance of ducting on 70 centimeters, 35 percent. Nothing toward Hawaii.

Events. The California QSO Party, now under way, California stations in demand. IARU Region 1UHF/Microwaves Contest, now under way. VHF-UHF FT8 Activity Contest, on Wednesday.

Club and community announcements. The SF Amateur Radio Club meets on the third Friday of each month, 7 PM at the Randall Museum. Visit sfarc.org for more details.

Check into a local net this week. Regular net practice is what makes emergency nets work.

Current weather conditions at San Francisco International Airport: Clear. Temperature 72 degrees Fahrenheit. Dew point 57 degrees Fahrenheit. Relative humidity 60 percent. Wind calm. Barometric pressure 29.84 inches of mercury, normal. Visibility 10 miles.

Batteries and radios in parked cars degrade in heat. Keep go-kit batteries somewhere cool.

National Weather Service forecast. Tonight: Partly cloudy, with a low around 62. West southwest wind 0 to 3 miles per hour. Sunday: Partly sunny. High near 85, with temperatures falling to around 77 in the afternoon. West northwest wind 1 to 12 miles per hour. Sunday Night: Mostly clear, with a low around 61. West southwest wind 0 to 9 miles per hour.

Tide predictions for today at the San Francisco Embarcadero gauge. High tide at 7:11 AM, 4.4 feet. Low tide at 11:12 AM, 3.5 feet. High tide at 5:11 PM, 5.8 feet.

Ocean and bay conditions. No marine advisories in effect. From the San Francisco buoy, 18 nautical miles west of the Golden Gate: significant wave height 4 feet, slight seas, dominant period 9 seconds, from the west northwest. Wind at the buoy 10 knots from the west northwest. Ocean water temperature 60 degrees Fahrenheit. San Francisco Bay water temperature 68 degrees Fahrenheit. Golden Gate currents: slack water at 3:01 AM, then maximum flood 1.9 knots at 5:40 AM, then slack water at 9:03 AM.

Air quality for field operations, from the Bay Area Air District's San Francisco Arkansas Street monitoring station. Fine particulate matter, PM2.5, is 14 micrograms per cubic meter, rated moderate. Ozone is 15 parts per billion. Nitrogen dioxide is 22 parts per billion. For more information visit the Bay Area Air District or openaq.org on the web.

Sign up for your county's emergency alerts, such as Alert SF in San Francisco. Hams are often among the first to relay that information.

Seismic awareness for emergency communicators: no Bay Area earthquakes of magnitude 2.5 or greater in the past 24 hours. Largest in California in the past 24 hours: magnitude 2.4, near Alum Rock. No earthquakes of magnitude 6 or greater worldwide. Seismic data from earthquake.usgs.gov.

After a strong earthquake, check in on your local emergency net, and keep transmissions brief to leave room for emergency traffic.