I don't think this takes into account the jammers such as the Chinese
music jammer or utility jammers.
Jim
Don't know of any standard time station operating on 20MHz at
present,other than WWV. Could be some utility/service transmission.
Could be one of those guys in Cuba running one of those transmitters
built from scavenged CFL parts.
Just kidding. One of the most interesting shows on shortwave is Arnie
Coro's DX'ers Unlimited on Sunday and Tuesday night on Radio Havana.
Unfortunately, Arnie has his head up his Communist ass these days with regards to keeping
RHC's transmitter plant properly working and also with jamming other countries
transmissions.