Report

Space weather: solar flux 105, 10 below its 90-day average of 115. Maximum usable frequency 26 megahertz, measured by the Idaho Falls ionosonde via KC2G: long-distance paths open through 15 meters, 12 meters marginal, 10 meters and up closed. Critical frequency 7.8 megahertz, so 80 and 60 meters are good for NVIS, 40 meters marginal. Daytime absorption limits 160 and 80 meters to short range. K index 1, very quiet. No significant flares. Data from NOAA.

Lower solar flux means the maximum usable frequency drops, so 20 meters becomes the main daytime DX band, and 40 and 80 meters do more of the work at night.

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, 47 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.

Moonrise or moonset is a few hours away. At low moon elevations, reflections off flat ground or water in front of a horizontal antenna can add several decibels, an advantage for coastal stations.

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: AMSAT's live status page shows which satellites are working. Check before a pass, and log your own reports to help others.

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: over Oakland, a duct at 210 to 560 meters, good for 2 meters and up. A matching duct over Vandenberg suggests a path to Southern California. K6EEG's experimental tropo model, from NOAA data, for the next 12 hours: Ducting continues along the Bay Area coast, strongest around 6 PM, and the Southern California coast, strongest around 3 PM. Ducting developing along the Pacific Northwest coast after 6 PM. Nothing toward Hawaii.

Tropo openings favor horizontal antennas. For CW, try 144.05 to 144.1 megahertz on 2 meters, and 432.1 on 70 centimeters.

Events. The California QSO Party, now under way, California stations in demand. IARU Region 1UHF/Microwaves Contest, now under way. IARU Region 2 Area GHFSSB Contest, now under way.

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.

Many handhelds can receive NOAA Weather Radio. Program the local channels.

Current weather conditions at San Francisco International Airport: All values in SI units. Temperature 22 degrees Celsius. Dew point 17 degrees Celsius. Relative humidity 73 percent. Wind calm. Barometric pressure 1012 hectopascals, normal. Visibility 16 kilometers.

Batteries and radios in parked cars degrade in heat. Keep go-kit batteries somewhere cool. Know how long your backup power lasts. Test it under real load, not just with a meter.

National Weather Service forecast. Values converted to SI units. Today: Sunny. High near 30 degrees Celsius, with temperatures falling to around 27 degrees Celsius in the afternoon. North wind 0.9 to 4.5 meters per second. Tonight: Mostly clear, with a low around 17 degrees Celsius. West southwest wind 0.4 to 4.0 meters per second. Sunday: Mostly cloudy. High near 29 degrees Celsius, with temperatures falling to around 24 degrees Celsius in the afternoon. Northwest wind 0.4 to 4.5 meters per second.

Tide predictions for today at the San Francisco Embarcadero gauge. High tide at 7:11 AM, 1.35 meters. Low tide at 11:12 AM, 1.08 meters. High tide at 5:11 PM, 1.77 meters.

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 1.1 meters, slight seas, dominant period 8 seconds, from the southwest. Wind at the buoy 3 meters per second from the northwest. Ocean water temperature 15 degrees Celsius. San Francisco Bay water temperature 19 degrees Celsius. Golden Gate currents: slack water at 1 PM, then maximum flood 0.7 meters per second at 3:44 PM, then slack water at 5:36 PM.

Air quality for field operations, from the Bay Area Air District's San Francisco Arkansas Street monitoring station. Fine particulate matter, PM2.5, is 13 micrograms per cubic meter, rated moderate. Ozone is 23 parts per billion. Nitrogen dioxide is 16 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.

If you smell gas, leave first. Use radios and phones only after you're at a safe distance.