Jsn, even with very good radios, you'll want more vertical separation than you can get in a single piece of PVC pipe. RG-58 will be unsuitable for this application due to high loss and inadequate shielding. It should also be noted that common PVC pipe introduces some losses at UHF.
Unless you have very short feedline runs, a duplexer and one decent antenna will be cheaper than buying the good-quality feedline you'll need for two runs to separate antennas. It will certainly be more trouble-free. UHF duplexers can be had for $100 or less at many hamfests. 73, Paul, AE4KR ----- Original Message ----- From: boozhoundlabs To: Repeater-Builder@yahoogroups.com Sent: Thursday, October 30, 2008 1:09 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
