Well Depending on how much power you will be using, you are looking to need at least 120' of direct vertical separation between the antennas which the RX antenna needs to be on the top and the tx on the bottom, and even then, your still talking about 65 dB of isolation in the best of conditions at 5 MHz separation. So quite frankly, no a good idea for everyday use.
________________________________ From: boozhoundlabs <[EMAIL PROTECTED]> To: [email protected] Sent: Thursday, October 30, 2008 3:09:48 PM Subject: [Repeater-Builder] 2-in-one antenna for UHF repeater? I am building an inexpensive UHF repeater. Rather than spend money on a duplexer, I am considering using 2 antennas. I have had good luck building small dipoles, and would like to build a collinear pair of vertical dipoles in a single PVC housing for send and receive. I am considering building the dipoles out of 1/2" copper with RG-58 running inside, and the whole thing sealed inside PVC pipe. As for the actual configuration of the antenna, I am still brainstorming options, and would appreciate help and experience narrowing things down. What would be the best spacing for a pair of dipoles in this collinear configuration? I would like to minimize interaction between them, or perhaps even provide gain based on their interaction. Any ideas how to adapt a design like the one below to dual-antenna configuration: http://www.repeater -builder. com/antenna/ wa6svt.html Can the part of the antenna connected to the coax braid be shared between antennas, with one ungrounded quarter wave section for Rx and Tx above and below? It would also be neat to have the Rx antenna be of higher gain than the Tx antenna since this will likely be used primarily by handhelds. Any suggestions of ways to do this? I am considering extending the Rx dipole with several 1/2 wave center-to-braid sections of coax as in most gain-ful collinear antennas. Thanks, jsn
