Ouch. I wasn't aware that much separation was needed. My application is for short term use in portable situations, and a 120' tower is completely out of the question.
I guess I'll continue to troll eBay for duplexers. Thank you for the reality check. jsn On Thu, Oct 30, 2008 at 3:01 PM, David Piche <[EMAIL PROTECTED]> wrote: > 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: Repeater-Builder@yahoogroups.com > 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 > > >
