Rat-Race

No

the frequency of each radio is different so a different length would be needed

and if it did work the transmitting radio would desensitise the receiving radios

http://www.google.co.uk/search?q=operating+multiple+radios+from+one+ariel&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GZEU_en&redir_esc=&ei=_ld6TO3lOc7p4gbevvDYBg

you may get away with a discone anttena this is an ariel that works on multiple frequencise able to recive and transmit

if it was me i would try a 1/4 wavelenth of each frequency coax cable feeding a T piece then onto the ariel make sure the feed from the T piece is not a multiple of either frequency

http://www.google.co.uk/search?q=discone+antenna+design&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GZEU_en&redir_esc=&ei=clh6TIWwA5iL4gbu97XHBg

http://www.google.co.uk/search?q=american+amatuer+radio&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GZEU_en&redir_esc=&ei=r1p6TPG3Mcv24gborry2Bg

sorry

Both you are radio users... and I commend that.. but I must say the word you are looking for is "Aerial"

not areal etc. shame shame...

Any such device is going to have insertion loss, something you may not find acceptable. Too, it should be subjected to lab testing, with applicable test equipment, to verify adequate isolation, else you may be back with the same problem (damaging another receiver).

The "rat race" device, or similar, does not exhibit the "Q"/selectivity needed and thus would not offer enough isolation in my opinion and certainly severe receiver desensitation would be realized.

Reconsider using two antenna systems with vertical separation.

Cell phones use a https://en.wikipedia.org/wiki/Duplexer which splits the incoming signal and the outgoing signal so the handset can simultaneously TX and rx from the same ariel.

https://www.globalspec.com/industrial-directory/circulator_duplexer

https://www.arrl.org/

https://www.hamradio.co.uk/acatalog/Accs_Duplexers.html

https://www.google.co.uk/search?hl=en&rls=com.microsoft:en-gb:IE-SearchBox&rlz=1I7GZEU_en&q=duplexer+circulator&revid=2012768533&sa=X&ei=0gh8TLjyAsLn4AaHmoGMBg&ved=0CEsQ1QIoBTgK

http://www.aerocommthailand.com/Div3/MicrowaveCatalog.pdf

http://www.ebooknetworking.net/ebooks/microwave-circulator-design.html