Unfortunately, it's been too long for me to speak with authority on the specifics of what energy levels would be safe to do that for. However, from what I recal

Unfortunately, it's been too long for me to speak with authority on the specifics of what energy levels would be safe to do that for. However, from what I recall, in general there shouldn't be anything preventing that at reasonably low power levels. You could also use something like: https://en.wikipedia.org/wiki/Waveguide_(radio_frequency) https://en.wikipedia.org/wiki/Waveguide_(radio_frequency)