Does anyone know why we use Affirm and Negative in RT, rather than Yes and No? I assume it's to prevent confusion with accents and other languages - but Yes and No sound very different to me!
Because it makes you sound cool and very Top Gun!
Seriously though, short words, especially at the end and beginning of transmissions are often clipped. When everything is busy, a question might only need a "yes/no" reply. Yes/no is easily lost in radio communication. Affirm/negative are not.
Also, with English native speakers, yes and no are absolute. In some languages, yes and no are relative to the question.
Of course, the question is not good as it contains a negative but, if a question can only have an "affirmative or negative" response, it also helps the questioner to form a good question:
This can only be "affirmative (always shortened to "affirm" to avoid confusion) or "negative". There is no interpretation.
Why do we say "TANGO" on the radio for the letter "T"? Because "T" could get garbled or misunderstood to be "B", "E", "or "V". "NO" could become "oh?", "YES" could become "us", and so on...the possible interpretations and permutations of short, monosyllabic words are many. Use a big word and it will be hard to confuse with others...
"Affirmative" and "Negative" come from the radio procedure words that went into the aviation world. As a comment above it also adds on more complexity and length to the statement so that the receiver can understand even if the transmission got garbled up or cut off in some parts. It would be really bad if the "yes" or "no" got cut off somehow from the transmission which would be really easy because they take a really short time to say, making it easy to loose the entire word over radio.
It has to do with how radios in general work or worked. This is also true with telephones and some VOIP situations.
So take a plain old radio. You set it to a frequency, then you push a button to talk. When you push the button a circuit completes that lets electricity flow through some components (used to be the mic, but now it's gone through changes at times, but it doesn't matter). Next the sound of your voice is encoded and applied over a carrier signal. Because that carrier signal can't be sent 100% of the time there was/is a bit of distortion at the start and end. In some radios they use a beep or click to help "establish" the carrier signal. Remember that the simplest radios just applied your voices wave form over that of the carrier signals.
Now, on the the receiving end, the same thing happens in reverse. The receiver can actually listen to the carrier signal the entire time, but there is a tiny delay as it starts to notice modulation of that signal, and starts "decoding it". Again remember the simple radio has your voice as a modulation of the carrier wave. These days there is a lot of logic on this end to filter out noise, but even if there wasn't it would still take a tiny amount of time to "see" that the carrier wave changed.
So you have several points of distortion and delay at the start and end of a message;
Add to that all kinds of distortion and interference, and the fact that as people we have a tendency to think along the lines of "push button -> talk" so fast that we often start "talking" before we are actually transmitting, and you can get some pretty messed up messages.
To combat that there are a few common things that are done.
For example (not from anything in particular):
While a bit odd all three could be understood if your having a conversation about dinner.
Is harder to understand then
Specially when you are asking a yes or no question.
So if you say into you radio "Do you want Pizza" and you get back: "...", your SOL. If you get back "oh", is that "oh I don't know" or the end of no? If you get back "Neg.." or "N....itive" or "Negiti.." Your still in good shape ( you have your answer).
There are many things radio operators are taught to do to make sure they can understand one another in less then perfect conditions. Using "longer" words is one, using distinct words is another, and using scripted responses and questions is a third. It's also important to remember that rarely is the radio a "primary job" it's almost always a "secondary job". The pilot needs to communicate, but communication can't be so cumbersome that it gets in the way of actually flying. So what ever system is in place to cover the distortion and what-not has to be easy, and widely understood.
If you had two people with training, and they were taught that the question: "Do you want pizza?" could only EVER be answered with "... Yes ..." or "... No ..." then you could use yes or no, they sound different. But that means that the operator answering would have to press the button, count in their head to three, say YES, then count in their head to three, finally releasing the button. However if that operator was distracted, and didn't wait, or if the operator was out sick and the new guy didn't know the protocol, or there was a large network of people asking the question all with slightly different protocols, now "...Yes..." doesn't work as well.
Because it increases the number of syllables being spoken thus increasing the likelihood of correct communication.