That could be GymLink, which is a simple 5 kHz LF transmission. It’s also used so that it can work while swimming. Here’s a discussion about it: https://www.ee

That could be GymLink, which is a simple 5 kHz LF transmission. It’s also used so that it can work while swimming. Here’s a discussion about it: https://www.eevblog.com/forum/rf-microwave/looking-for-a-receiver-for-5-khz/ https://www.eevblog.com/forum/rf-microwave/looking-for-a-rec...