[600MRG] reformatted question on Path Loss

[Edward R Cole]

Neil,

I don't think there any path loss formulae for ground wave propagation.

Only formula I know is for free space loss (line of sight):
L = 32.4 + 20log(F) = 20Log(d) in dB, where:
F = MHz and d = km

For 475-KHz = 0.475 MHz:
L= 32.4 - 20.78 + 20Log(d) = 11.6 + 20 Log(d)

d= 249km, L = 11.6 + 47.9 = 59.5 dB
d= 373km, L = 11.6 + 51.4 = 63.0 dB

But this does not predict loss over ground and 
curvature of Earth, nor estimate loss for obstructions.
Maybe something was experimentally determined 
from early use of MW and LF but it would seem 
that other propagation modes would mess up any calculations.

But then the estimate that GW will reach 350mi comes from something.

Most of my professional path loss calculations 
dealt in either d = meters or d = millions of 
km.  The first usually is near field radiation 
which does not behave in the inverse square of 
distance (20Logd) and the second one deals with 
interplanetary distances on frequencies that can penetrate the ionosphere.

I'd be interested to hear of any calculation for ground wave.

73, Ed - KL7UW

At 01:19 PM 8/11/2015, Neil Klagge wrote:
>  (I had to re format this email. It got 
> mushhhhed together the first time, HI)
>
>Anyone know how to make use of this formula for 630m ground wave predictions?
>
>Path loss  in (dB) , PL = 22+20 Log W
>Where W equals number of wavelengths from the source
>
>I dont recall where I got this from some time 
>ago. I was comparing the PL between me and Rudy, 
>and between  me and John Gibbs, VE7BDQ.
>
>I was getting a PL of ~74 dB between me and Rudy 
>(249km), and a PL of ~77 dB between me and John 
>(373km) up near the "other Vancouver". And yet, 
>I am seeing (in the database) a difference 
>between their decodes of my XSV of about 10 dB during daytime.
>
>Dont know what to make of it...
>
>
>*´¨)
>¸.•´¸.•*´¨) ¸.•*¨)
>(¸.•´ (¸.•`   Neil
>
>My Faith website: http://neilsfaith.webs.com/
>My ham radio websites: http://w0yse.webs.com/ and http://wg2xsv.webs.com
>
>
>
>
>
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73, Ed - KL7UW
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