Report

Space weather: solar flux 105, 9 below its 90-day average of 114. 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 4.0 megahertz, so 80 meters is marginal for NVIS. K index 4, 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 7:08 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, 32 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.

Grayline enhancement on 80 through 40 meters is strongest within about half an hour of sunrise and sunset.

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: the ISSAPRS digipeater is on 145.825 megahertz. Packet stations can send position reports through space.

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 16 hours ago: Newer data is not yet available, and conditions may have changed. over Oakland, a duct at 800 to 1100 feet, 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 5 AM: ducting expected on 70 centimeters, 90 percent; a chance of ducting on 2 meters, 50 percent. Southern California coast, peaking around 11 PM: ducting expected on 70 centimeters, 95 percent; ducting likely on 2 meters, 65 percent. Pacific Northwest coast, peaking around 11 PM: ducting likely on 70 centimeters, 75 percent; a slight chance of ducting on 2 meters, 25 percent. 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, 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.

Current weather conditions at San Francisco International Airport: Clear. Temperature 73 degrees Fahrenheit. Dew point 52 degrees Fahrenheit. Relative humidity 47 percent. Wind calm. Barometric pressure 29.90 inches of mercury, normal. Visibility 10 miles.

National Weather Service forecast. Tonight: Mostly clear, with a low around 61. West southwest wind 0 to 9 miles per hour. Monday: Sunny. High near 81, with temperatures falling to around 75 in the afternoon. West northwest wind 0 to 10 miles per hour. Monday Night: Mostly clear, with a low around 60. West southwest wind 2 to 9 miles per hour.

Tide predictions for today at the San Francisco Embarcadero gauge. Low tide at 12:34 AM, minus 0.1 feet. High tide at 8:16 AM, 4.7 feet. Low tide at 12:48 PM, 3.3 feet. High tide at 6:32 PM, 5.6 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 3 feet, slight seas, dominant period 15 seconds, from the south southwest. That's long-period ground swell. Wind at the buoy 10 knots from the west northwest. Ocean water temperature 61 degrees Fahrenheit. San Francisco Bay water temperature 67 degrees Fahrenheit. Golden Gate currents: maximum ebb 3.1 knots at 11:14 PM, then slack water at 4:09 AM, then maximum flood 2.1 knots at 6:50 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 6 micrograms per cubic meter, rated good. Ozone is 46 parts per billion. Nitrogen dioxide is 7 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 2.5, near Pinnacles. 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.