The transmission speed in air would be very close to a vacuum, so the speed of light (c). This depends on the velocity factor [1], for pure copper it's 0.95 c,

The transmission speed in air would be very close to a vacuum, so the speed of light (c). This depends on the velocity factor [1], for pure copper it's 0.95 c, so 95% the speed of light. Actually for air, according to this source [2], the velocity factor is 0.999707085823853610892 c. [1] https://lowpowerlab.com/guide/rf-best-practices/velocity-factor/ https://lowpowerlab.com/guide/rf-best-practices/velocity-fac... [2] https://www.qsl.net/ac5jw/isbp/vf.html https://www.qsl.net/ac5jw/isbp/vf.html