I am really new at electronics projects. I am trying to build a repeater out of two mobile VHF radios and I'm not sure how to solve a problem I am having:

My main problem is with the radio that I want to transmit. It does not have VOX mode on it and I'm not sure how to get the first radio to trigger the second radio to transmit. Is there a simple way to do this or do I actually need a radio with VOX capability?

Thanks in advance for any and all help I may receive!

-David.