Lower power consumtion in battery operated radio's.
Easy maintenance (tube replacement).
Best listening pleasure & nice woodcase.
No damage through Electromagnetic pulse (EMP).
"Magic eye" possibility as signal level indicator.
Vacuum tube detector circuit in vintage A.M. radio's.
An audion receiver can use a single tube to detect and amplify mw / shortwave signals.
A QSL card is a written confirmation of either a two-way radiocommunication between two amateur radio stations or a one-way reception of a signal from an AM radio, FM radio, television or shortwave broadcasting station for the listener. A typical QSL card is the same size and made like a typical postcard.