Hi everyone, I'm still pretty new to HF and trying to understand when the bands are actually going to be good for DX. I see people talking about Solar Flux Index but I'm confused about what numbers I should be looking for. I've read that 150+ is good, and some say you want it above that for several days, but yesterday I saw SFI at 140 and 20m was dead all afternoon. What am I missing here?

Also, what's the deal with the K-index? Someone told me you want it below 3 but I'm not sure how much that really matters compared to the solar flux numbers.

Welcome to HF! The key thing about SFI is that it needs to be maintained for some days to build up ionization in the F2 layer. A single day of SFI 140 after several days of low numbers won't give you great conditions. Also remember that geomagnetic activity (high K-index) can depress the MUF even with decent solar flux.

I was confused about this too when I started! Generally conditions are OK when A-index is 10 or lower, K-index is 3 or lower, and SFI above 90. But like W5XYZ said, you need sustained higher numbers for the really good DX. Check out VOACAP predictions for your specific path too.

For best conditions, solar flux should remain above about 150 for a few days with K index below 2. When these conditions have been met, check out the bands and expect some good DX to be about! Time of day matters a lot too - try again during peak hours for your target area.