According to Reed Hundt, VHF/UHF television frequencies can extend (unlicensed) wireless broadband to everyone. The lower frequency penetrates trees and walls. But is 700Mhz really better?
Vyyo says their 700 MHz broadband wireless system can provide broadband to thousands within a 25 mile radius of a tower. Their “wireless cable modem” (below) claims 25Mbps down, and 4 Mbs up.
Polar Communications, uses Vyyo’s 700 Mhz gear (in the backhaul) for subscribers in North Dakota and Minnesota.
What kind of range and speed might we expect at 700 Mhz? YDI’s System Operating Margin calculator might help with some rough estimates.
It’s not a valid comparison, unfortunately, because the YDI calculator assumes the modulation standards, channel bandwidth and the sensitivity of the two radios would be the same. They would not be. For example, 6Mhz television channels are narrower than the 20Mhz Wi-Fi channels. That means data rates will be lower (perhaps 20Mbps vrs 54Mbps). Narrower bandwidth also increases gain (and range).
Still, if we use Part 15 rules and keep everything the same, using identical sensitivity, power, and antenna parameters, changing only the frequency from 2.4 Ghz to 700Mhz, we can get an indication of the range improvement. You can use YDI’s System Operating Margin calculator to estimate range: 
First, plug in typical 2.4 GHz WiFi parameters:
- Operating Frequency: 2.4 GHz
- Tx Power: 23dB
- Tx Antenna Gain: 15dB
- Rx Antenna Gain: 2dB
- Cable Loss (total): 5dB
- Rx Sensitivity: -85dB
- System Operating Margin: -20.2 dB
- Distance between Antenna: .6 miles
Next, calculate again, changing only the frequency to 700 Mhz:
- Operating Frequency: 700 MHz
- Tx Power: 23dB
- Tx Antenna Gain: 15dB
- Rx Antenna Gain: 2dB
- Cable Loss (total): 5dB
- Rx Sensitivity: -85dB
- System Operating Margin: -20.5dB
- Distance between Antenna: 2 miles
It looks like 700 MHz gets 3 times the range. That’s using a maximum of 4 watts EIRP (+36dB). Feeding a 23dB radio into a 15 dB antenna (minus 2-3dB loss) results in maximum legal power of +36dB (4 watts).
It might enable 2.4 mile mobility (using 802.16e), from an unlicensed 700Mhz base station. And that, perhaps, is what 700 Mhz is really all about.
If you substitute a +18 dB client antenna, range extends to 3.5 miles (at 2.4Ghz) and 13 miles (at 700Mhz), according to the YDI calculator. Handy for Intercontinental WiFi, too.
Wouldn’t it be great if ordinary “hotspots” could backhaul up to 15 miles using “wireless DSL” and wouldn’t it be great if unlicensed 802.16e could give licensed cellular a run for its money.
It might happen.
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