MW Frequency Channel

**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?

**Finetopix** · 2011-06-23 04:04 AM

**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

Originally Posted by ritgail

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???

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.

Originally Posted by harrypotter

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.