At the end of a contact with a friend, most hams will call out a hearty “73.” It’s so popular that you may see ham radio operators sign “73” at the bottom of an email or even social media post.
The formal definition of 73 is “Best Regards” – it’s a nice way to say goodbye that is unique to amateur radio.
But, have you ever stopped to think why we use that number to end a contact? The answer takes us all the way back to the days of landline telegraphy.