NEC-LIST:Boom effect in yagi arrays

Dear NEC-lister,

I note that recently there have been some postings to NEC-list re the
above matter.

I believe that the first to have made a recommendation on how to account
for the effect of the boom in the case where the yagi elements are in
conductive contact with it were by Fishenden and Wiblin in 1949. The
reference is R M Fishenden and E R Wiblin, "Design of Yagi Aerials",
Proc. IEE, Pt III, vol. 96, no. 39, January 1949, p. 50 et seq. Their
paper reports work which was carried out by them around 1940 at the
Telecommunications Research Establishment, later it the War located at
Malvern, as part of British radar development. F&W's recommendation is
to add three quarters of the boom diameter to the element lengths,
provided that the boom diameter remains small compared with the average
element length, a result that they arrived at empirically. I have used
this result myself in yagi design but have never seen any modern support
for it (or correction of it!) using the computing resources we now have
available, but it would be interesting to do so.

Anyone interested in the historical background to this work may like to
consult C Latham and A Stubbs, "Pioneers of Radar", Sutton Publishing
Ltd., 1999.

Harry E. Green,
Adjunct Research Professor,
Instiute for Telecommunications Research,
University of South Australia.

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