@steve69 I could back to the 1930s where certain communication receivers were used right through to the 1960s
The National HRO receiver was one of those receivers and Tesla worked for that company in the 1930s using his mothers surname of Turbo on the the receivers...The HRO was probably the only communications receiver to rely on coils for band changing, and you can still find them on places like Ebay for sale...And remember Tesla was highly skilled in creating specialised coils, he produced some of them for The Philadelphia Experiments ship, named the Eldridge (DE173)

The National HRO receiver was one of those receivers and Tesla worked for that company in the 1930s using his mothers surname of Turbo on the the receivers...The HRO was probably the only communications receiver to rely on coils for band changing, and you can still find them on places like Ebay for sale...And remember Tesla was highly skilled in creating specialised coils, he produced some of them for The Philadelphia Experiments ship, named the Eldridge (DE173)

