Comprod makes dipole arrays with a screen reflector, at least for VHF, not sure about UHF. I'm looking in the catalog and it shows a backside null close to 20 dB down from the main lobe.
The screen reflector should be nominally about 1/4 wave behind the radiator for maximum forward gain. It could be modeled fairly easily. How wide of a forward beamwidth do you want? Would a couple of corner reflectors be a better way to go? --- Jeff > -----Original Message----- > From: Repeater-Builder@yahoogroups.com > [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Dan Hancock > Sent: Thursday, November 19, 2009 11:43 AM > To: repeater builders > Subject: [Repeater-Builder] Antenna Pattern Question > > > > I have a repeater that I need to have as tight a cardiod > pattern as possible. I have looked at the dipole antennas > such as the DB-411 and they don't really shut down the back > door quite enough. > Does anyone have any antenna modeling software that would > show the result of adding an 18" wide screen to the back side > of the mast on the DB-411? Does anyone have any experience in > home-brewing a modification like this? > > Dan Hancock N8DJP > > > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.425 / Virus Database: 270.14.61/2498 - Release > Date: 11/19/09 07:51:00 > > >