Telling your quads apart by ear

At a meetup this summer there were three of us at one folding table, all on Bluejay, and two of us had the Mario theme flashed. Batteries going in left and right, goggles half on, and I honestly couldn't tell whether the quad that just played was mine.

That's when I started giving every quad its own tune. Not a song, more like a ringtone. Three or four notes that mean "this is the 5-inch" or "this is the whoop".

Why bother

The startup melody plays once when the battery goes in. That moment already tells you power reached the ESCs. With a distinct tune per quad it also tells you which quad you just powered. I've found that handy when:

• I've got my goggles on and plug in by feel
• several quads sit on the same table at a meet
• I've lent a quad to a friend and want to hear from across the field that they've plugged in the right one

It won't stop you doing anything silly, of course. It just tells you what you plugged in.

What makes a good signature

Short is the whole point. I aim for under two seconds. A full song works too, but then it's back to being music rather than an ID, and you end up waiting for the chorus before you've recognised it.

The trick is to make them differ in more than one way. Two tunes that only differ in key sound almost the same from across a table, at least to my ears. Change the rhythm, the direction, or both. My current set:

whoop:d=16,o=6,b=160:c,e,g,4c7
five:d=8,o=5,b=140:g,g,4c6
tooth:d=16,o=6,b=180:e,p,e,8a
lr:d=4,o=5,b=100:c,g4,2c

The whoop runs quickly up an arpeggio and lands high. The 5-inch does two repeated notes and a jump. The toothpick is a little stutter with a gap in it. The long-range rig is slow, dips down and comes back. You'd never mix them up, even half-listening.

A few rules I ended up with after some trial and error:

1. Match the character to the quad. A tiny whoop with a deep, slow tune is funny once, then it's just confusing.
2. Give each one a different first note. Your ear decides very early which one it's hearing.
3. Stay in octaves 5 and 6. In my experience very low notes get mushy on small motors and very high ones get thin.
4. Test at the field, not at the desk. Wind, chatter and other quads change what's recognisable. More on that in field testing your tune.

If you want something more personal than my little arpeggios, the pentatonic approach from composing your own tune works well here. Just stop after four notes.

Same string on every motor?

For an ID tune I put the same string on all four ESCs. It's the simplest option and the unison is loud and clear. You could split a chord across the motors (see the polyphony post), and I tried that on the 5-inch for a while, but the chord blurred the identity a bit. A single line is easier to pick out of background noise.

If some of your quads run AM32 or BLHeli_32, strings this short fit on any of them. BLHeli_32 tops out around 48 notes, and these use four.

Write it down

Once you've got a set, note which quad got which string. I keep mine in the same text file as everything else, with the quad manifest I described in managing your tune library. Sounds like overkill for four notes. Then you reflash an ESC and can't remember whether the toothpick went "da-da-DUM" or "da, da-DUM", and suddenly it isn't.

I'm curious whether anyone has done this across a whole club, with everyone registering a signature so nobody doubles up. It would make a busy meetup table sound a lot less like a slot machine.