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ritgail
2011-06-23, 04:04 AM
Say I have been given three spots for MW planning...7GHZ,15GHZ,18GHZ

Which frequency should i use for long and short backhaul MW link and why?

How do i divide the spots into channels for planning in Pathloss?

harrypotter
2011-06-23, 04:50 AM
7 Ghz for long haul. The lower your frequency the farther it can go, look at your wavelength formula c/f. Look at ETSI/ANSI for channel plans. The highest you can go for 7Ghz is 40Mhz bandwidth. Check the ANSI/ETSI epsecification.

tanbao
2011-06-23, 05:06 PM
Say I have been given three spots for MW planning...7GHZ,15GHZ,18GHZ

Which frequency should i use for long and short backhaul MW link and why?

How do i divide the spots into channels for planning in Pathloss?

Hi friends,

for 7GHz, you should use for long haul cause the attenuation in rain and pathloss is very low, depend on the capacity and channelize you will have several bandwidth such as : 28MHz, 29.5MHz, 40MHz...
for 15GHz, 18GHz, you can use for short backhaul depend on the distance and criteria of your country

ritgail
2011-06-23, 06:54 PM
Ok i got it right, higher frequency for shorter HOP.. but if lower band such as 7GHz is used for urban area..it will require more height for fresnel clearance ?

Next for channel a band, please guide how to divide, does it depends upon modulation and carried traffic?

harrypotter
2011-06-23, 07:06 PM
Again, its not practical to use 7Ghz for short hops. By regulation, 7Ghz doesnt allowed to be deployed for short distance. Use 23 Ghz, 18, Ghz, 15Ghz in case. ir use the 70, 80 and 90 Ghz for less than a mile.

ritgail
2011-06-23, 07:38 PM
I have the calculation, where fresnel radius is shown. for lower bands it is bigger radius.. is it the fact???


http://www.finetopix.com/picture.php?albumid=44&pictureid=100

calculation R=17.3√{d1d2/f(d1+d2)}

7GHz has 6m for 100%, 15 GHz 4.6m difference is 1.5m approx...

for 60% clearance it will require higher tower as per result.



Again, its not practical to use 7Ghz for short hops. By regulation, 7Ghz doesnt allowed to be deployed for short distance. Use 23 Ghz, 18, Ghz, 15Ghz in case. ir use the 70, 80 and 90 Ghz for less than a mile.

Stantheman
2011-06-23, 08:06 PM
yes , that is correct, the fresnel zone radius increase with lowering of frequency.

some good resources:-

Fresnel zone - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Fresnel_zone)

Fresnel zone calculator and antenna height calculator - RF path analysis -www.afar.net (http://www.afar.net/fresnel-zone-calculator/)

Support :: Calculations :: Fresnel Clearance Zone :: Terabeam Wireless (http://www.terabeam.com/support/calculations/fresnel-zone.php)

just search "fresnel zone" in Google and there is more info than you can read