I created a logo where the "i" in "Promise" is a radio tower, with the signal coming off of the cross. It is spreading the word, as well as the light—thus, I have a glow coming off of it as well. Simple and direct, and I think it is easily recognizable as a Christian radio station. Instant recognition is extremely important, especially with radio stations where you may only get a billboard to spread your word to convince someone to tune in.
Let me know if you would like to see any changes, and I will be happy to provide them.