[Towertalk] 468/f

[jljarvis]

>And for how long did 468/f rest resplendent in the books,
>unquestioned, until Joe Common Ham got his mits on antenna modeling
>software?"

When I was a kid, the ARRL handbook offered 468/f as an approximation 
of the length of a dipole @ 1/2 wave height.  It was stated rather clearly 
that trimming would be required to accomodate site-variables.  

Last week, I cut an 80m dipole using 468/f as a starting point. Went up as
an inverted Vee.  Took perhaps 10 minutes with a meter to trim off a foot 
from each end, precisely as expected.  (I always add a foot on 80 & 40,
just to give me room to trim.  THAT they didn't put in the handbook!)   

Evidence suggests that 468/f is still a workable approximation.

It would seem that Joe Common Ham may suffer from an over-reliance on 
model data, or a lack of common sense in applying it.

Perhaps it's the expectation that you can predict unseen environmental 
variables with any precision whatever.  

Jim Jarvis, N2EA
Essex, VT