Report

Space weather: solar flux 105, 10 below its 90-day average of 115. Maximum usable frequency 10 megahertz, measured by the Idaho Falls ionosonde via KC2G: long-distance paths open through 40 meters, 30 meters marginal, 20 meters and up closed. Critical frequency 3.2 megahertz, too low for NVIS right now. K index 5, minor geomagnetic storm. No significant flares. Data from NOAA.

Geomagnetic storms can open aurora on 6 and 2 meters. Point north and listen for raspy, buzzy signals. 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 7:08 AM, sunset 6:48 PM, day length 11 hours 40 minutes. Moonrise 12:27 AM at 58 degrees, east northeast; moonset 3:40 PM at 299 degrees, west northwest. Waning crescent, 38 percent lit. The Orionid meteor shower peaks Wednesday, October 21, a meteor scatter opportunity on 6 and 2 meters. Moonbounce: the moon peaks today 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.

Rooftop solar inverters shut down at sunset, often lowering the HF noise floor for the evening. They come back on at sunrise.

Amateur satellite passes for the next four hours. AO7, linear transponder: at 8:14 AM rising in the north northeast, 86 degrees, overhead. AO 91, FM: at 9:49 AM rising in the south, 33 degrees. The ISS, FM crossband repeater, when active: at 10:30 AM rising in the southwest, 85 degrees, overhead. For the next pass, AO 91: uplink 435.25 megahertz with a 67 hertz tone, downlink 145.96. 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 15 hours ago: Newer data is not yet available, and conditions may have changed. 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 6 PM: ducting likely on 70 centimeters, 65 percent; a slight chance of ducting on 2 meters, 15 percent. Southern California coast, peaking around 3 PM: ducting likely on 70 centimeters, 75 percent; a chance of ducting on 2 meters, 30 percent. Nothing toward Hawaii.

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

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 18 degrees Celsius. Dew point 12 degrees Celsius. Relative humidity 68 percent. Wind calm. Barometric pressure 1012 hectopascals, normal. Visibility 16 kilometers.

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: Partly sunny. High near 29 degrees Celsius, with temperatures falling to around 25 degrees Celsius in the afternoon. West northwest wind 0.4 to 5.4 meters per second. Tonight: Mostly clear, with a low around 16 degrees Celsius. West wind 0.0 to 4.0 meters per second. Monday: Sunny. High near 28 degrees Celsius, with temperatures falling to around 24 degrees Celsius in the afternoon. West wind 0.0 to 4.5 meters per second.

Tide predictions for today at the San Francisco Embarcadero gauge. Low tide at 12:34 AM, minus 0.02 meters. High tide at 8:16 AM, 1.42 meters. Low tide at 12:48 PM, 1.00 meters. High tide at 6:32 PM, 1.72 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 1.0 meters, slight seas, dominant period 8 seconds, from the northwest. Wind at the buoy 2 meters per second from the west northwest. Ocean water temperature 15 degrees Celsius. San Francisco Bay water temperature 19 degrees Celsius. Golden Gate currents: slack water at 9:03 AM, then maximum ebb 0.8 meters per second at 11:39 AM, then slack water at 2:32 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 6 micrograms per cubic meter, rated good. Ozone is 6 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 2.4, near Alum Rock. No earthquakes of magnitude 6 or greater worldwide. Seismic data from earthquake.usgs.gov.

Secure radio equipment and shelving. A falling power supply or radio can take your station out of action at the moment it's needed most.