Report

Space weather: solar flux 105, 10 below its 90-day average of 115. Maximum usable frequency 17 megahertz, measured by the Idaho Falls ionosonde via KC2G: long-distance paths open through 20 meters, 17 meters and up closed. Critical frequency 6.0 megahertz, so 80 and 60 meters are good for NVIS. Daytime absorption limits 160 and 80 meters to short range. K index 4, minor geomagnetic storm. 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, 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.

VHF and UHF tropospheric enhancement is often strongest from sunset to early morning, when a nighttime temperature inversion forms.

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: rotate a handheld Yagi as the satellite passes to follow its changing polarization. A small twist can bring back a fading signal.

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 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 8 PM: ducting expected on 70 centimeters, 90 percent; a chance of ducting on 2 meters, 55 percent. Southern California coast, peaking around 2 PM: ducting likely on 70 centimeters, 60 percent; a slight chance of ducting on 2 meters, 15 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.

Current weather conditions at San Francisco International Airport: Temperature 73 degrees Fahrenheit. Dew point 61 degrees Fahrenheit. Relative humidity 65 percent. Wind calm. Barometric pressure 29.89 inches of mercury, normal. Visibility 10 miles.

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. Today: Partly sunny. High near 89, with temperatures falling to around 80 in the afternoon. Northwest wind 2 to 10 miles per hour. 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.

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 8 seconds, from the northwest. Wind at the buoy 6 knots from the west. Ocean water temperature 60 degrees Fahrenheit. San Francisco Bay water temperature 66 degrees Fahrenheit. Golden Gate currents: slack water at 2:32 PM, then maximum flood 1.3 knots at 4:58 PM, then slack water at 6:58 PM.

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 12 micrograms per cubic meter, rated good. Ozone is 24 parts per billion. Nitrogen dioxide is 19 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.