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 5.5 megahertz, so 80 meters is good for NVIS, 60 meters marginal. Daytime absorption limits 160 and 80 meters to short range. K index 4, minor geomagnetic storm. 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 7:08 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, 36 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 9:02 AM, 71 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. SO 50, FM: at 12:07 PM rising in the southwest, 44 degrees. For the next pass, SO 50: uplink 145.85 megahertz with a 67 hertz tone, downlink 436.795. Send a 74.4 hertz tone briefly first to start its timer. Frequencies and live status at amsat.org/status. Pass predictions at n2yo.com.

Satellite tip: keep FM satellite contacts short, callsign and grid square, so everyone gets a turn.

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 250 to 330 meters, good for 33 centimeters and up. No matching ducts along the coast or toward Hawaii, so the enhancement is likely local. K6EEG's experimental tropo forecast, based on NOAA atmospheric model data, for the next 12 hours. Bay Area coast, peaking around 10 PM: ducting expected on 70 centimeters, 85 percent; a chance of ducting on 2 meters, 45 percent. Southern California coast, peaking around 1 PM: a chance of ducting on 70 centimeters, 50 percent; a slight chance of ducting on 2 meters, 10 percent. Nothing toward Hawaii.

Tropo openings favor horizontal antennas. Calling frequencies, upper sideband: 144.2 and 432.1 megahertz.

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.

Check into a local net this week. Regular net practice is what makes emergency nets work. Test your go-kit monthly, and rotate batteries and supplies.

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 1013 hectopascals, normal. Visibility 16 kilometers.

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 0.9 meters, slight seas, dominant period 15 seconds, from the south southwest. That's long-period ground swell. Wind at the buoy 2 meters per second from the north northwest. Ocean water temperature 16 degrees Celsius. San Francisco Bay water temperature 19 degrees Celsius. Golden Gate currents: maximum ebb 0.8 meters per second at 11:39 AM, then slack water at 2:32 PM, then maximum flood 0.7 meters per second at 4:58 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 16 micrograms per cubic meter, rated moderate. Ozone is 13 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.

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.

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