A pair of Just Add Power entry level 3G TX/RX (707POE/508POE) with some power supplies would do this simple 4K extension with no problem. Phase and all that other stuff just being tossed about in this thread won't matter. We'll gladly send you a pair to test to prove it. Send me a PM or an email (ed @ justaddpower dot com) when you are ready to solve the problem.
Ed Qualls - Just Add Power - Proud to advertise on and support Remote Central