180 vps is standard for Kleinschmidt and 87.5 is standard for Teletype Corp. I have a 120 vps tuning fork also, but have never found where it was used. Duncan K2OEQ On 11/24/2019 12:49, John, W9DDD wrote: > What uses a 120 CPS tuning fork? I've heard of 180 and 87.5ish. >