6m- Randomly opened, in random directions. I think this happens more in the day, but I'm not a 6m expert. Strictly speaking this is VHF, not HF, but it's often included on HF rigs.
10m- This is more consistently opened, especially in times of higher solar activity. Evening tends to be the best time, at least that's what I've found, but this is a daytime band.
12-17m- These are traditional daytime bands, usually opened. The longer the band in this window, the more reliable it is, and the more likely it is opened night or day.
20m- Can be opened day or night. This is the most reliable band for dx.
40m- Daytime is opened in a "local" area, give or take 500 km or more with a good set up. Night time opened worldwide.
80m- Similar to 40, but even more extreme.
160m- This one is only opened at night, and tends to be a more local area. Not unlike 6 meters, strictly speaking this is MF rather than HF, but it's often included on HF rigs.
Very good band breakdown. Looking to get into 6m eventually. I have a radio that does it, but it's a QRP rig, so only 5 watts RF. Better suited to a quiet mountain top and a long wire antenna.
Long being a relative term on 6m when a buddy pole Dipole is only about 9.5 feet. I love the randomness of the 50Mhz band but if I'm looking to contact you on the west coast from the Midwest I better understand that 40m might not be the ideal band to use at noon. Better to try 20 or higher, 17? 15? Or if we're looking at the time zone difference it's 21:00 here but 19:00 there, maybe a better idea is to swing lower to 75m LSB and give you a call.
@Patriotic Trucker I have made a few 75m contacts at about 6;30pm Pacific Time with my Atlas 210x and an Outbacker antenna in the backyard. Talked to hams in Oregon, Washington, Sacramento, and Ogden, Utah using about 95W rf. But it was difficult as the noise level here is about S9. Looking forward to getting out of the city and moving up onto a hill where my Mom has some property. Should be much quieter radio wise up there.
For those who may not know but CB is located between 10 and 12 meter ham bands. CB behaves very much the same way and the use of the sidebands is very popular for long distance CB contacts. A "good" Choice for a CB is any choice that has SSB capabilities such as a Galaxy 959, uniden 980, cobra 148GTL and gtldx (discontinued?)
I have the uniden 980 it's been peaked and tuned by a reliable radio shop ,installed an Astatic noise cancelling microphone. On a good day or night I can receive and transmit out past 3 miles in ether direction. Using a 4 ft. Antenna and rg58 coaxial cable.
On the CB , don't know about the USB or LSB , haven't been able to find another person who has that capability on their radio.
@Steven Stanford right now is a bad time to play as the solar Activity is very low, you've probably heard Bear talk about the grand soloar minimum. It plays havoc but generally follows an eleven year cycle when the magnetic poles of our star flips