GHz versus Watts

[kermit911]

I am looking for a camera for my WALL-E robot my son and I are building. The reference material we are using suggests and audio video transmitter / receiver to be able to transmit up to a mile. I found a few, but I am confused on how the GHz make a difference. 1.2 GHz at 2 watts can transmit about 2000 to 5000 meters. If the transmitter / reciver was, lets say 5 GHz at 2 watts would it make a difference? What do GHz have to do with the transmition of the video / audio?

Thanks
Dave

[Buenchico]

While it would be wrong to state that the frequency of radio signals is unrelated to the distance that they can be received over, you probably won't notice much difference between a 1.2Ghz transmitter and a 5 Ghz one.

1.2GHz is in the upper end of the UHF (ultra high frequency) band, whereas 5 GHz is in the lower end of the SHF (super high frequency) band. UHF is used (among many other things) for terrestrial TV signals, with a typical main transmitter having a power of around 250,000 Watts. SHF isn't normally associated with radio or TV signals. It's most common uses include wi-fi connections (which use very low power) and radar systems (with quite high power).

For your purposes it's likely that 1.2 GHZ might be somewhat better than 5 GHz but neither is totally impractical. It would probably be more important to concentrate on finding out which frequencies (if any) you can get a licence for. I can find nothing within the technical section of the Ofcom website to suggest that unlicensed operation of equipment within the frequency bands you refer to is permitted. Indeed, the frequencies you've mentioned (1.2 GHz and 5 GHz) are alarmingly close to those used by aircraft navigation systems.

Chris

[ll_billym]

I agree with Buenchico, a lot of frequency bands are licensed and 5km is a long way to be able to transmit.

The bands 2.4GHz and 5GHz are unlicensed for use with WiFi products but I am pretty sure there is a limit to the signal power a single device can produce (otherwise there would be too much interference between devices) and I would say you will be lucky to get 200m out of it, especially streaming video/audio which will require the use of high data rates.

[kermit911]

So I guess the watts would be what gives you the range, not the frequency? If you have 400 MHz at 1 watt or 1.2 GHz at 1 watt you wont get that much difference in distance?

[ll_billym]

Correct, but reading into it, the permitted power level for 5 GHz band is higher than 2.4 GHz so you can legally get longer distance.

Some good info here:
http://www.solwise.co...etworkingwireless.htm
http://www.solwise.co.uk/wireless-5.htm