I just wanted to ask something about FREQ Bands and how they work?

In the Day the Bands LF/MF will not pass through the D Layer of the Ionosphere and get absorbed.

The Bands that will pass through are UHF/VHF/SHF/EHF.

So am I Right in the Day nothing will come back down and skip?

 

What does AI have to say?

At night, the D layer disappears. Signals below 2MHz gets reflected.

3 to 30MHz gets refracted off E and F layers.
15-30MHz skip is possible during daytime.

https://www.qsl.net/4x4xm/FAQ/What-is-Skywave-Propagation.htm

 

I just wanted to ask something about FREQ Bands and how they work?

In the Day the Bands LF/MF will not pass through the D Layer of the Ionosphere and get absorbed.

The Bands that will pass through are UHF/VHF/SHF/EHF.

So am I Right in the Day nothing will come back down and skip?

No, that is not right. Radio Amateurs are able to work longer distances during the day and during the night.
Of course, conditions vary, and the mechanism of propogation varies a fair amount. So, "Never Say Never" is what applies. Certainly the solar radiation does cause a layer of greater ionization, and that does tend to provide a more reflection. BUT that is not the whole story. This is definitely an area where the simple answer is simply wrong. Consider that the amount of water vapor present also has an effect.

 

Then there is electromagnetic noise... The lower bands can become nearly unusable in the summer months due to the noise generated by lightning discharges. Then there is Earth created Geomagnetic noise and Solar noise from the Sun's various emissions both normal emissions and those from Solar Flares and Coronal Mass Ejection emissions and their effects on the Earth's Geomagnetic emissions and the various layers of our atmosphere. Along with the man-made soup of electromagnetic emissions. In the HF world Solar Weather is an important part of spectrum usability along with the Earth's Geomagnetic conditions.

 

Certainly NOISE also has a big effect on what frequencies can be best used for communications. That is totally correct. And much of the noise is beyond human control. And a whole lot of it is cyclic and varies with the time of day, and the frequency being considered. So the effect on a specific frequency is variable.