I had a couple of friends who had ZX81's and CB radios and they managed to transfer a program using the radio succesfully back then. Was not long after that CB

I had a couple of friends who had ZX81's and CB radios and they managed to transfer a program using the radio succesfully back then. Was not long after that CB radio fad kicked in and the ability to find a unused channel for along enough period ended for them. But they did it and it worked, least for the ZX81 audio storage format used upon tapes. iirc it was stored on tape at 300 baud, so the bandwidth was low requirement.