Question T3C09
From subelement T3 - T3C
What is generally the best time for long-distance 10 meter band propagation via the F region?
Why is this correct?
Answer A is correct because the 10-meter band requires enhanced ionospheric ionization for F-region propagation. During high sunspot activity, increased solar radiation creates maximum ionization during daylight hours (dawn to shortly after sunset). The other choices are wrong because: B suggests nighttime propagation when solar ionization is reduced; C and D involve low sunspot periods when insufficient ionization exists for reliable 10-meter F-region skip.
Memory tip
Remember the pattern: higher frequency HF bands (like 10 meters) need MORE ionization, so they work best during peak solar conditions AND peak solar hours. Lower frequency bands can work with less ionization, making them better for nighttime. This sunlight-frequency relationship helps predict propagation across all HF bands.
Learn more
The 10-meter band sits at the boundary between HF and VHF frequency privileges, requiring maximum ionospheric enhancement for reliable DX communication. During sunspot maxima, the enhanced F-region ionization during daylight hours can support propagation on frequencies up to 50 MHz. This creates exciting opportunities for worldwide communication on 10 meters using modest power levels and simple antennas, making it popular for DXpeditions and contest operations.
Think about it
Why do you think 10-meter propagation is so dependent on sunspot activity while 40-meter propagation works well even during sunspot minimums?