tinaeuc

So I had to go with a switch..
only one radio at a time to listen and transmit.
thanks for all the help.

Thanks I think this will do.

If you are wanting to have two or more radios on a single antenna you are out of luck..... you need two antenna's one for transmit and one fore receive... If you are willing to run 2 antenna's you can run a control station combiner that allows you to run as many radios as it has ports.  4 is usually the minimum but 8 is more common and they can be expanded to 32 ports which is the largest I have seen. With tow antenna's. 
Now the pricing isn't for the faint of heart, typically about a grand per port on the smaller ones and can get down to 500 per port on the larger units.  Plus of course the two antenna's required.  Signal loss though these is pretty high as well.  Looking at 6 dB both directions.  SO a 50 watt radio will have 12.5 watts out, but it's typical to turn the radios down to 20 watts so you are looking at 5 watts out.  Incoming signal is also 6dB down so you need to be fairly close to the repeaters you are talking to.
 

As far as I know, you can't listen on two radios at the same time AND be able to transmit on either of them, one at a time or otherwise.  Even a switch won't make that possible unless you are using two switches to completely cut out the other listening radio before transmitting. 
 
Duplexers are frequency split and directional.  So, that is off the table.
 
Diplexers are also frequency split, but support two-way communications on the same frequency.  However, each side of the split typically has a vast enough frequency split that two radios can't transmit and receive on the same frequency on both sides of the split.  Most of the time, they are band splitters. One side being VHF and the other UHF or one side is VHF/UHF and the other is HF/MF.
 
Some T splitters (which are very affordable), but not all, would allow you to receive on both radios at the same time.  However, you can't transmit without destroying the other listening radio.
 
So, that really only leaves a T connector and two auto-sensing or manual switches.  Keep in mind that there will be a small amount insertion losses, but you are facing potentially high expense. 
 
Frankly, even using 2 high-end auto-sensing switches is risky... I wouldn't do it.
 
Keep in mind, I don't know everything and I am not aware of every device or method out there.  This is just from my experience and training.  Someone else may have a better answer.
 

I used one of these, MFJ-1702 2 Position Antenna Switch, for that purpose a long time ago. GigaParts has them for around $40. I am sure there are other brands and venders out there.

I would like to do something similar so following to see what is recommended.