Browsing local electronics forum I noticed an interesting post about dangerous radio receiver.
Link to Lithuanian forum post.
Short summary - someone bought a small AC powered FM radio in local market place and noticed
"tingle" in metal antenna. Electronics repairman deduced that this is because
AC mains is connected to antenna via diode bridge, meaning no isolation. It is not a capacitive coupling, test with light bulb proved it to be direct. See added pictures with traced circuitry.
Obviously, such design is very
dangerous (and 99.99% illegal).
Other posts suggested that some USSR period (and older western/chinese) radio designs also have antenna connected to mains via diode bridge or autotransformer. As a remedy installation of proper isolation transformer or high voltage caps in series with antenna were suggested.
Question - do you know of any common radio that has antenna connected to mains? Is this an old design practice (from times when earth was not used and live chassis were common)? Or is it rather stupidity of a designer?