More of a info question

[headhunter23]

Was thinking over the weekend, doesn't the high ghz wireless telephones advertise that they get 10km range. I probably don't have enough background to understand why they can't transfer that technology over to video/radio range? I'm assuming it would be illegal to use the same frequencys or whatever.

Ivan.

[eickst]

The ones I have seen advertising 10km range are operating on the 268 and 394mhz frequencies. The base will xmit on one and receive on the other, and the handset will do vice versa.

Plus those are transmitting at half to one watt output power.

[Mr.RC-Cam]

Modern cordless phones are using digital spread spectrum modulation. The FCC rules allow higher RF power with digital modulation (up to 1W, with exceptions to 4W). On the other hand, our wireless video systems are allowed a bit less than 0.001W for license free use in the USA (0.01W in other countries).

The spread spectrum video systems are currently bulky, expensive, and have noticeable response lag. One day this may change, but for now it is what it is.

Just as important is that effective RF range is a function of RF bandwidth; the bandwidth for video is quite large. So generally speaking, watt for watt, wireless audio apps will always have much longer range than wireless video apps. It's the nature of the beast.

[headhunter23]

Interesting thanks for the info.