~20ms delay? How do I do it?

[EBK]

Longer delays by bouncing off . . . the Moon.

Now we're talking coolness factor!

[PRR]

Moon-bounce is 2,400mS to 2,700mS (two and a half seconds).

Wikipedia has a sound-clip of talking off the moon, and it says you can hear an echo, but I don't.
https://en.wikipedia.org/wiki/Earth%E2%80%93Moon%E2%80%93Earth_communication

Voice is already at/past the limit for good speech quality over such a lousy link. (Some better with gigantic equipment, but that's an uphill fight.) Most practical contacts are good old knuckle-code or slow pulse techniques.

[EBK]

Moon-bounce is 2,400mS to 2,700mS (two and a half seconds).

Wikipedia has a sound-clip of talking off the moon, and it says you can hear an echo, but I don't.
https://en.wikipedia.org/wiki/Earth%E2%80%93Moon%E2%80%93Earth_communication

Voice is already at/past the limit for good speech quality over such a lousy link. (Some better with gigantic equipment, but that's an uphill fight.) Most practical contacts are good old knuckle-code or slow pulse techniques.

If I ever find cause to build a simple buffer pedal, I think I will label it "Moon-bounce lo-fi delay" and put transceiver send/return jacks on it for giggles. 

[Processaurus]

if you can live with it being 12.3 ms, or 24.6ms, you can use a PT2396 in "easy mode". It is a single chip delay processor that can go shorter than the pt2399 that everyone uses here. Easy mode uses 4 dip switches to set the delay time.

http://www.sdiy.org/destrukto/datasheets/PT2396.pdf