Report

Space weather: solar flux 105, 10 below its 90-day average of 115. Maximum usable frequency 16 megahertz, measured by the Idaho Falls ionosonde via KC2G: long-distance paths open through 20 meters, 17 meters and up closed. Critical frequency 5.1 megahertz, so 80 meters is good for NVIS. K index 3, unsettled. No significant flares. Data from NOAA.

The declining phase of the solar cycle often brings some of the cycle's strongest flares and geomagnetic storms, so VHF aurora openings on 6 and 2 meters are still very possible.

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, 43 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.

After sunrise the D layer builds, and 160 and 80 meters go quiet on daytime paths within an hour or two.

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: on 70 centimeter downlinks, Doppler shift is about plus or minus 10 kilohertz. Start high at rise and tune down through the pass.

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 5 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 3 AM: ducting expected on 70 centimeters, 85 percent; a chance of ducting on 2 meters, 45 percent. Southern California coast, peaking around 12 AM: ducting expected on 70 centimeters, 85 percent; a chance of ducting on 2 meters, 40 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.

Current weather conditions at San Francisco International Airport: Clear. Temperature 75 degrees Fahrenheit. Dew point 57 degrees Fahrenheit. Relative humidity 54 percent. Wind calm. Barometric pressure 29.82 inches of mercury, normal. Visibility 10 miles.

Know how long your backup power lasts. Test it under real load, not just with a meter.

National Weather Service forecast. Tonight: Mostly clear, with a low around 62. West wind 0 to 5 miles per hour. Sunday: Partly sunny. High near 83, with temperatures falling to around 75 in the afternoon. Northwest wind 1 to 10 miles per hour. Sunday Night: Mostly clear, with a low around 61. West southwest wind 2 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 12 knots from the northwest. Ocean water temperature 61 degrees Fahrenheit. San Francisco Bay water temperature 67 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.

If you feel a strong or long-lasting earthquake near the coast, move to high ground immediately. Don't wait for an official tsunami warning.

Air quality for field operations, from the Bay Area Air District's San Francisco Arkansas Street monitoring station. Fine particulate matter, PM2.5, is 9 micrograms per cubic meter, rated good. Ozone is 25 parts per billion. Nitrogen dioxide is 15 parts per billion. For more information visit the Bay Area Air District or openaq.org on the web.

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 2.9, near South Lake Tahoe. No earthquakes of magnitude 6 or greater worldwide. Seismic data from earthquake.usgs.gov.

Know your local emergency net frequencies, and test your radios on battery power regularly.