Omnidirectional antenna pattern distortion...

[mazou]

Is there a tool that can model the effects on the radiation pattern of a omnidirectional antenna placed on the side of a telecom tower? Are there critical distances(in function of wavelenghts) to avoid in placing the antenna? Most antenna manufacturers give these "distorted" radiation patterns for small distances between antenna and tower (1 lambda, 1.5 lambda, 1.75 lambda...etc). Is there a critical distance(versus a specified tower face lenght) at which the towers distortion is approx. nul? Any help would help...By the way, this is for the 800Mhz band...
thanx

 

[VEBill]

Tools:

NEC - You could use the usual NEC type programs, but at certain frequencies and structure sizes the problem becomes computationally intractable due to the number of elements required. The computation goes up as F^3.

EZNEC is one example:

http://www.eznec.com/index.shtml

GTD/UTD approaches the problem differently such that large structures can be modeled at high frequencies (something NEC can't do without a supercomputer or lots of time).

Best example is:
ALDAS by Antenna Software Ltd.

http://www.maasdesign.co.uk/

http://www.maasdesign.co.uk/aldas.html#linkName7

Although the primary application for ALDAS is antennas on aircraft, this software is also intended for use with modeling antennas on lattice masts. ALDAS is not inexpensive.


J. Harvey
Ottawa

 

[jbartos]

Suggestion: Visit

http://www.qsl.net/ac6la/

http://www.cebik.com/nec.html

http://members.fortunecity.com/xe1bef/software-antennas.htm

etc. for more info