[NLRS] Path loss calculations
[email protected]
[email protected]
Thu, 4 Mar 2004 22:52:20 CST
Look at QEX July/August 2003. There is an article
titled "Microwave Propagation in the Upper Troposphere"
I will have to reread it, but there are some equations in there
that may help estimate the path loss over free space.
See the ARRL UHF/Microwave Experimenters Manual
p. 3-9 for the full info on the equations that I use for
free space calculations. Check out p. 3-23 for equations
that give estimates of the loss on a Troposcatter path.
I couldn't find the graph that I have which shows
troposcatter path loss, but I did find some other info.
I don't know where it came from the notes are hand written
and many years old. The part we are interested in says,
"A useful rule of thumb for tropo forward scatter is as follows:
At a 100 mile range the median field strength is approximately
57dB below the free space value and a further loss of about
0.12 dB per miles occurs at greater distances. Depending on
the degree of reliability required an allowance of 8 to 16 dB
should be made for slow fading and a further allowance
of 3 to 8 dB for Rayleigh type fading. This propagation
mode is effective for ranges up to about 350 miles but
useful narrow band signals can be received at a distance
of 600 miles." This is talking about commercial quality
signal levels for a wideband signal. I will have to see how
this compares with the info in the Experimenters Manual.
73, Gary WB0LJC
On Thus, 4 Mar 2004 20:48:55 EST [email protected] writes:
>
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>In a message dated 3/4/2004 6:43:41 PM Central Standard Time,
>[email protected]
>writes:
>1) FSK = 36.6 + 20 Log (Frequency in MHz) + 20 Log (distance in
>Miles)
> the result is in dB. FSK is free space path loss.
>
>This the only equation that I wonder about. There may be two
>problems with
>it. One is that this is the free path loss for two stations who can
>see each
>other while a tropo contact is based on the fact that two stations can
>see a
>common scattering volume in the troposphere but the scattering loss
>needs to
>be accounted for. The second is the 20 Log (fred) part .... I think
>it must
>take into consideration a standard antenna on all frequencies like
>perhaps a
>dipole or something.
>
>It would be good to find an equation that defines tropo scatter path
>loss.
>
>73, Jon
>W0ZQ
>
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><dtmf><HEAD>
><METAL char set=3DUSK-ASCII help-equip=3DOcument-Type
>content=3D"text/html; cha=
>rset=3DUS-ASCII">
><META content=3D"MSHTML 6.00.2800.1400" name=3DGENERATOR></HEAD>
><BODY style=3D"FONT-SIZE: 12pt; FONT-FAMILY: Arial; BACKGROUND-COLOR:
>#fffff=
>f">
><DIV>
><DIV>In a message dated 3/4/2004 6:43:41 PM Central Standard Time,
>wb0ljc@ju=
>no.com writes:</DIV>
><BLOCKQUOTE style=3D"PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT:
>blue=20=
>2px solid"><FONT face=3DArial>1) FSPL =3D 36.6 + 20 Log (Frequency in
>MHz) +=
> 20 Log (distance in Miles)<BR> the result
>is in=20=
>dB. FSPL is free space path loss.</FONT></BLOCKQUOTE></DIV>
><DIV> </DIV>
><DIV>This the only equation that I wonder about. There may
>be tw=
>o problems with it. One is that this is the free path loss
>for t=
>wo stations who can see each other while a tropo contact is based on
>the fac=
>t that two stations can see a common scattering volume in the
>troposphere bu=
>t the scattering loss needs to be accounted for. The
>second is t=
>he 20 Log (freq) part .... I think it must take into consideration a
>standar=
>d antenna on all frequencies like perhaps a dipole or
>something. =
> </DIV>
><DIV> </DIV>
><DIV>It would be good to find an equation that defines
>troposcatter pat=
>h loss.</DIV>
><DIV> </DIV>
><DIV>73, Jon</DIV>
><DIV>W0ZQ</DIV></BODY></HTML>
>
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