RE: [Repeater-Builder] DB-224 Tower Side Mounting

[rob . vance]

Tower distortion is always an issue when side mounting on a tower, the larger the tower face the larger the distortion to the pattern. Yes mounting at greater distances off the tower will effect pattern / reduce distortion from tower, but increase the mechanical torque the mount and antenna can place on the tower, as well as the level of difficulty in mounting the antenna.  At 1/2 wave spacing off a Rohn 25 results in minimized distortion to an omni pattern VHF,  with a 42 inch face your going to likely have to get out 1 wave length in order to minimize the distortion, that is out a long way.  Yes you can phase two 224s together,  a bit of a spendy fix if you have to buy the second antenna and/or pay rent for tower space, but it can be done.  This approach may fix some of your close in holes off the back of the tower, but will have a negative impact on total range as compared to the current single antenna.  While your antenna pattern has some holes, it also has some coverage areas that receive a positive benefit from the current power and antenna arrangement,  if you half the power to feed a second antenna the ERP off the existing antenna is going to be cut to 1/2 of its current level.  This reduction in ERP and antenna performance could have a negative effect for some users in some areas.  Phasing two verticals together can certainly have an impact on radiation pattern,  that impact will be the result of the spacing between the two antennas, each antenna and the tower, and the real unknown factor of how much shielding the tower provides between the two antennas.   You will likely have to run a field test to see if there is indeed benefit.   I've done this on commercial two-way applications and had fairly good omni results on a 72" tower with the antennas mounted right up against the tower, but on opposite sides.   Good Luck, Rob  K7EI   -----Original Message----- From: Joel Mele [mailto:[EMAIL PROTECTED] Sent: Monday, August 16, 2004 2:03 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] DB-224 Tower Side Mounting Has any one solved the problem of omni directional pattern distortion when side mounting a DB-224 on a tower ?   I've side mounted several DB-224's using the DB 5001 side mount kit.     The results agreed with the radiation pattern supplied by Decibel Products, i.e. a distortion of the omni pattern and signal attenuation off the tower leg that the antenna is mounted on.   Will different mounting distances off the tower leg improve the omni pattern ?   Can a 224 be mounted on each side of the tower with a phasing harness or power divider ?   BTW, the tower I'm using has a 42" face.   Any ideas will be appreciated.   TNX...Joel W4SLH 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 the Yahoo! Terms of Service.