Hi
     Yes, they do make such a device called a duplexer or malty plexer. 
Usually expensive but sometimes well worth the money. I used to own one but 
never used it in the shack. I am sure others on the list can tell you much 
more.

God bless,
Mark
God loves you!
My ham radio lists.
http://lists.topica.com/lists/funhamradio.
http://groups.google.com/group/funhamradio-list
----- Original Message ----- 
From: "Colin McDonald" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, December 19, 2007 3:53 PM
Subject: multiple radios, one antenna


> here is a question for the list:
> I want to have my main VHF/UHF transceiver hooked up to my single dual
> bander, while at the same time using that same dual band antenna for 
> another
> transceiver and a scanner at the same time.
> I don't want to have to manually switch the antenna over to the different
> radios via an antenna switch.
> What i need is some sort of distribution device that will allow me to
> transmit on either of the VHF and or UHF radios, without damaging either 
> the
> other transceiver or the scanner.  And then when there is no rf being
> transmitted, to be able to have all 3 receive properly using the one
> antenna.
> My question is, is there such a device availible?
> I know about distribution amplifiers for receive, but i don't know if you
> can transmit through those, and i also need something that will prohibit 
> any
> rf getting back into the other radios.
> I know that any receiver that is on the same band will be desensatized as
> soon as I transmit, but i am not concerned about that since if i were 
> using
> a separate antenna, that would occur in the near field anyway.
> I require such a device because i can only really have one good dual band
> antenna at any height and i have several different rigs i want to be able 
> to
> use to monitor and transmit on, as well as listen on the scanner.
> I know that in multi-frequency systems, such as a public safety
> organization, or even public transit, they often have multiple radios on 
> the
> same band going at the same time for dispatch or communications purposes,
> all using the same antenna....i suspect they use some sort of tuned 
> cavities
> to prevent desensatization...
> I need a little box that i can plug my antenna into, and plug 3 radios 
> into
> the other side and not worry about my 50 watts of rf on VHF getting back
> into the antenna jack of the other radios and blowing out the front ends.
> any help is appreciated in finding a solution to my wishes.
>
> 73
> Colin, V A6BKX
>
>
>