Rod, The idea here is to get as much vertical seperation as possible, it doesnt sound to me like you have enough seperation if both antennas are mouted to a station master tube. Also, the rule of thumb is, the more gain an antenna has, the better vertical isolation you get. Yagi's have good gain and characteristically a huge null off the side, so if you mounted yours vertically, you would get optimal isolation. This explains the better result with a yagi. I would suggest more vertical seperation, at least 100 feet on VHF and at least 35 on UHF. Also use good verticals with at least 6 dBi gain or so, this will help buy some more isolation. If you dont have the tower for it then I would suggest a duplexer, its much cheaper than the tower would be.
Hope that helps, Wade - KR7K ----- Original Message ----- From: <[EMAIL PROTECTED]> To: <[email protected]> Sent: Sunday, January 16, 2005 11:47 AM Subject: [Repeater-Builder] Antenna Seperation > > I am sure this has been asked before, but I did a search archive on > the subject and came up with 0. I have a GR 300 repeater with no > duplexer, so I need 2 antennas. I tried a Larson mobile antenna w/ > the ground radials as the receive antenna and the same for the tx > antenna. These are mounted on a Station Master type antenna tube > (the guts were pulled out because it was untunable for 2 meters). > The rx ant at the top and the tx ant at the bottom, about 12' to 14' > separation. The system would talk to it self. I removed the tx ant and > replaced with a 4 ele yagi - works good. I need a omni ant for both > rx and tx. I have an Isolator on the tx and a Bp cavity and a > circulator on the rx. Why would it desense with one ant and not the > other ant? I know the idea behind the yagi and the mobile ant. But > they both have rf going vertical. I need to have minimal separation > without it talking to it self. Your ideas? Thank you. > > Rod > > > > > > > Yahoo! Groups Links > > > > > > > > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
