On 3/16/16 12:31 AM, Larry Loen wrote:
A friend of mine told me that someone, somewhere had calculated a "magic"
length for guy cable. If you went down 10 or 11 or 13 feet (or whatever it
is) off of your tower and installed your first insulator there, your guys
would be sufficiently 'non-resonant' so that they wouldn't interfere with
the pattern of the antenna(s) above.
What is this magic length and where is it documented?
There's a table in the ARRL Antenna Book of "good" guy segment lengths..
I do it by setting up an excel spreadsheet that calculates the number of
wavelengths for my frequencies of interest for a given length, and then
just making sure they're not close to a multiple of 0.5
if cell C3 is the frequency (in MHz) and cell A5 is the length (in ft)
C4 = 3.28*299.7/C3 wavelength in feet
C5 = $A5/C$4 - floor($A5/C$4) frac part of guy length in wavelengths
Then conditional format C5 to be red if it's in the range 0.45-0.55 (or
whatever tolerance you want)
I put a sample sheet out on google docs
https://docs.google.com/spreadsheets/d/1rXeWjPMej_TlzN0h8OfzEFAU2mwKGiar_QaxK94tozA/pubhtml
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