thanks Mr Fry for posting this interesting graphic. Just to clarify: 60 radials are 1/4 wave and 60 radials [appear to be] 1/8 wave, is that correct?
73, K3VAT --------------------------------------------------------------- Message: 3 Date: Tue, 1 Jul 2014 05:33:21 -0500 From: "Richard Fry" <[email protected]> To: <[email protected]> Subject: Topband: Affect of Unequal-length Buried Radials on Monopole Radiation Patterns Message-ID: <6DAF464A56C14D45A843BED5D592B464@ToshLaptop> Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original >Here is a clip of a post I made on another website in answer to a question >there, which might be of interest here also... Below is a link to a graphic from a NEC4.2 study showing how unequal-length buried radials affect the groundwave fields of a 1/4-wave monopole, for approximately the conditions given in the opening post. The h-plane fields are uniform +/- 0.014 dB. The ~304 mV/m groundwave fields calculated by NEC over these real earth paths are rather close to the ~306 mV/m inverse distance field ("efficiency") that the FCC predicts for this power and distance for a 1/4-wave, base-fed monopole driven against 120 buried radials, each 1/4-wave in length. Changing earth conductivity in that NEC model to 1 mS/m d.c. 5 (other parameters the same) changes the groundwave field to about 259 mV/m at 1 km, with a circularity of about +/- 0.12 dB. http://s20.postimg.org/vn85ii9kd/Monopole_Unequal_Length_Radials.jpg R. Fry _________________ Topband Reflector Archives - http://www.contesting.com/_topband
