在業餘無線電論壇和電子郵件線程中，業餘無線電運營商通常會使用" 73"或" 73s"，否則可能會希望找到"真誠"或"問候"。為什麼？
The usage of "73" for such a purpose comes from the Phillips Code, originally devised in the era of telegraphs to speed up transmission of common messages by mapping them to numbers.
"73" mapped to "best regards" or "my compliments" and was intended as a general valediction for transmitted messages.
It is still used for that purpose today in morse code transmissions and often makes its way into everyday correspondence among hams as a form of jargon.
There is also "88" (which maps to "love and kisses") that sometimes takes the place of "73" for communications between affectionate parties.
73 is, as Amber said, Phillips code for best regards or my compliments. I just wanted to add that it's redundant to say 73s, which amounts to Best Regardses or My Complimentses. This puts one in mind of Smeagol, talking to Hobbitses.
Most of these things come from morse code. They were used because they have a distinctive and musical signature, listen to the rhythm of '73' some time. Rhythm was (and should still be) the mark of a good operator. Alas, some non military operators in the early days were not, that is where 'ham' came from: because the operators sounded 'ham-fisted'. When I was a young boy my navy father taught me an exercise for learning rhythm it is: best bent wire / g Try it out some time on your morse key, you will be surprised how it improves your musicality.
If I say best regards to you it would be 73. If I and in a group or a net there are many people hence 73's, plural. It originated from code, person to person, singular. IMO, best regard(s) , Jerry W5JRY
See a list of jargon here: https://www.qrz.com/page/hamspeak.html
73 de TF8HA
On morse code you want your transmissions to be as short as possible and so they have developed codes for frequent words or phrases. 73 is the code for best wishes, sincerely, etc.