Terman's graphs show that T/A sig levels are strongest during peaks of the
solar cycle. Whereas the correlation that Laurie described is T/A success
when sunspot numbers are low.
My guess is that both are probably true, i.e. on average T/A signal levels
are better during the active part of the cycle, but conversely weak signals
are more likely to be disrupted during the active part.
We will probably find that at the low point of the cycle chances of getting
across are worse but consistently worse, if you follow me.
Send a cool gift with your E-Card