[TowerTalk] Coax Losses on 160 and 75?

[jimlux]

On 8/12/16 11:53 AM, TexasRF--- via TowerTalk wrote:
> And the results are intuitively obvious for even the most casual observer,
> right?
>
> The pdf mentions 1/4 and 1/8 wavelength multiples. Can we take it that
> random lengths do not work for the concept?
>

They work, but the math gets more complex.  the transmission line 
equations have a lot of terms that go to one or zero when you've got an 
exact multiple of pi/2.   And pi/4 (1/8 wavelength) is often a nice 
special case (e.g. sin(pi/4) = cos(pi/4))

It's all hyperbolic sine and cosine (with complex numbers).

It is NOT generally suitable for hand calculation (or even 
pencil/paper/calculator).. but you can do it in a Excel spreadsheet, or 
use something like Octave, Matlab, Mathematica, etc.

Excel does do complex math, but you have to build the hyperbolic 
functions using IMEXP(x)  (complex e^x)

imsinh(x) = improduct(0.5,imsub(imexp(x),imexp(improduct(-1,x))))
imcosh(x) = improduct(0.5,imsum( imexp(x),imexp(improduct(-1,x))))

if you're doing a lot of calculations with the same argument x, you can 
build some intermediate results that make life easier.  exp(-x) = 
1/exp(x), for instance. so imdiv(1,imexp(x)) is the same as 
imexp(improduct(-1,x))..




> 73,
> Gerald K5GW
>
>
>
> In a message dated 8/12/2016 1:41:50 P.M. Central Daylight Time,
> steve at karinya.net writes:
>
> http://www.karinya.net/g3txq/wet_ll/tl_formulas.pdf
>
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