hello
Jeff
i am very thank full to your help, i have got Rx height 101.2

Regards
naqvi

wrote in message
oups.com...
hello
Jeff
i am very thank full to your help, i have got Rx height 101.2

Regards
naqvi

Who is right, you or Jeff? You are more than 100% off from each other.

In truth, i could receive that signal holding a hand held 10GHz receiver
while sitting on the ground. The 80m hill is nothing from an observer 10KM
away...only .006 degree from the top of the transmitter tower. It is part of
the horizon. I love it when you guys talk like you are sol knowledgeable yet
lack the common sense to conceptualize the problem as it really exists.

" In truth, i could receive that signal holding a hand held 10GHz receiver
while sitting on the ground. The 80m hill is nothing from an observer 10KM
away...only .006 degree from the top of the transmitter tower. It is part
of the horizon. I love it when you guys talk like you are sol
knowledgeable yet lack the common sense to conceptualize the problem as it
really exists.

So you are saying that you can achieve 30km at 10GHz to a hand held receiver
at ground level with a 300 foot hill in the way!!! I am sure that you could
not do this with any sensible power even at 2m let alone 10GHz.

Perhaps it is your concept of what is going on that is wrong. Have you heard
of Fresnel Zones??
When obstructions come within the first Fresnel zone significant attenuation
occurs.

With the situation that you are describing the path is totally obstructed,
with the path only possible due to diffraction from the hill top. The hill
top impinges to at least the top of the 5th Fresnel Zone, hence the
attenuation is very high.

As the height of the Rx antenna increases the attenuation is still very high
until the hill top only start to intersect with of the first zone (antenna
height~150m). It then drops quite rapidly until there is true line of sight
and bottoms out when the hill top is clear of the second zone.

You make a great deal of the hill only being 0.006 degree at the horizon. If
you plot it accurately and with reference to the Fresnel zones, it does make
a big difference. With the Rx antenna at ground level the top of the Fresnel
zones are never below the horizon, which is completely different to the
situation when the hill is there (-5th Zone obstructed).

Also, without the hill you only have to raise the Rx antenna to about 15m to
achieve line of sight compared to 200m with the hill there!!!!!! Quite a big
difference I think you will agree, and one that your 'conceptualisation
doesn't seem to allow for!!

73
Jeff

wrote in message
oups.com...
hello
Jeff
i am very thank full to your help, i have got Rx height 101.2

Regards
naqvi

Please show your work.

"Stefan Wolfe" wrote in message
...

wrote in message
oups.com...
hello
Jeff
i am very thank full to your help, i have got Rx height 101.2

Regards
naqvi

Please show your work.


Hi Stephan

Your posts seem to inply that the receive antenna will "see" the 20 meter
high transmitting antenna when the receiver antenna is in the shadow of the
80 meter hill. It seems that the receiver needs to be out of the shadow of
the hill unless you are able to estimate refraction from the hill.

But, your aparent confidance in the statement "0 feet" makes me wonder if
I have this problem wrongly analyzed. I have so much confidance in Richard
Fry's data that I had accepted his estimation of 270 meters to be as close
as you can estimate.

Do I misunderstand your post about what minimum height is needed?

Jerry

wrote:

The total distance between the transmitting and receiving antenna of a
microwave link at 10GHz, is 30 Km. the height of the Tx antenna is
above ground level is 20 m. the maximum acceptable total path loss is
169 dB. Furthermore there is hill located 10 km away from the
transmitter antenna with a height of 80m.

calculate the height of the receiver antenna for the path loss to be
just equal to the maximum acceptable value?

Whats the height of the receive antenna?

Is the hill directly in the line of sight of the receive antenna?

The total distance between the transmitting and receiving antenna of
a microwave link at 10GHz, is 30 Km. the height of the Tx antenna is
above ground level is 20 m. the maximum acceptable total path loss is
169 dB.
Furthermore there is hill located 10 km away from the transmitter (Tx)
antenna with a height of 80m.

calculate the height of the receiver antenna for the path loss to be
just equal to the maximum acceptable value?

Whats the height of the receive antenna? (required)

Is the hill directly in the line of sight of the receive antenna?
yes it is b/w the LOS

wrote:


The total distance between the transmitting and receiving antenna of
a microwave link at 10GHz, is 30 Km. the height of the Tx antenna is
above ground level is 20 m. the maximum acceptable total path loss is
169 dB.
Furthermore there is hill located 10 km away from the transmitter (Tx)
antenna with a height of 80m.

calculate the height of the receiver antenna for the path loss to be
just equal to the maximum acceptable value?

Whats the height of the receive antenna? (required)

Is the hill directly in the line of sight of the receive antenna?
yes it is b/w the LOS

At 10 Ghz the "hill" is a factor if the receive antenna is at the same
elevation or below.
If its higher it really is a non factor, if this remains true I would be
more concerned with shifts in temperature and if the signal travels over
a body of water.

wrote
The total distance between the transmitting and receiving antenna of a
microwave link at 10GHz, is 30 Km. the height of the Tx antenna is
above ground level is 20 m. the maximum acceptable total path loss is
169 dB. Furthermore there is hill located 10 km away from the
transmitter antenna with a height of 80m.

calculate the height of the receiver antenna for the path loss to be
just equal to the maximum acceptable value?
_____________

The height above mean sea level of the tx and rx sites, and the terrain
profile for the path would be necessary to answer this ~ accurately. But
for a smooth earth model, the graphic at the link below will give some
insight.

It shows that a height of around 270 meters would be needed for the receive
antenna, using a K-factor of 1.33 and 0.6 fresnel clearance for an 80 m hill
10 km downrange. The path loss then would be about 142 dB.

http://i62.photobucket.com/albums/h8.../10GigPath.gif

RF

On 7 Feb, 15:43, "Richard Fry" wrote:
wrote The total distance between the transmitting and receivingantennaof a
microwave link at 10GHz, is 30 Km. the height of the Txantennais
above ground level is 20 m. the maximum acceptable total path loss is
169 dB. Furthermore there is hill located 10 km away from the
transmitterantennawith a height of 80m.

calculate the height of the receiverantennafor the path loss to be
just equal to the maximum acceptable value?

_____________

The height above mean sea level of the tx and rx sites, and the terrain
profile for the path would be necessary to answer this ~ accurately. But
for a smooth earth model, the graphic at the link below will give some
insight.

It shows that a height of around 270 meters would be needed for the receiveantenna, using a K-factor of 1.33 and 0.6 fresnel clearance for an 80 m hill
10 km downrange. The path loss then would be about 142 dB.

http://i62.photobucket.com/albums/h8.../10GigPath.gif

RF

hi

Richard
i have read ur response very carefully and its perfect 142dB Path
loss but problem is that what's the Rx height
if i suppose Tx and Rx install on the same height
then my Rx height after the earth buldge and knife e calculation
i have got 100m Rx
its totally wrong
because
if i increase that (100m) Rx height its mean get the problem at
fresnel Zone

need help

thanks
regard

naqvi