I've been doing research on radio transmitters, and though I understand how the signal is generated and how data is transmitted, I still can't understand what defines a radio's transmitting power. How is a certain transmitter more powerful than the other?
Electronic – What Makes a Radio Transmitter Powerful
radioRF
Related Solutions
Very nice study.
Slides:
An Analysis of Power Consumption in a Smartphone
Conclusions:
Major consumers:
display & cell radio
WiFi power low in most situations
CPU can be significant
Future power driver
Where power is not going:
- RAM
- Audio
- Bluetooth
- Storage
Korean study.
27 slides - results differ somewhat from above.
Energy tradeoffs in smartphone apps
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For data transmission / reception, one of the less expensive options today is a pre-built module around the nRF24L01+ Transceiver IC. These modules typically offer a built-in PCB-trace antenna, 250 Kbps to 2 MBPS bandwidth before error correction, and are tried and tested.
Most important, they save you time in debugging and antenna tuning. After thousands of people have used these modules, which are built on the manufacturer's reference designs after all, most of the kinks are pretty thoroughly ironed out. Also, being able to tap the experience of many others on the internet who have used such a module, counts for a lot when trying to resolve issues.
For instance, this listing on eBay is for a mere US$2.10 with free international shipping. It uses the 2.4 GHz band, which does not need licensing for low power use in most countries.
Another alternative is this 433 MHz band transmit / receive pair of modules (just 9.6 Kbps though), in case you specifically want to stay with transmit-only and receive-only designs. US$1.99 for the pair makes it pretty attractive.
Of course, in each case, you could as well build your own module starting from the IC manufacturer's reference design, and thus learn while implementing your radio functionality.
It is unlikely that the price advantage of massive volume production can be beaten, though.
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Best Answer
Very simply, transmitter is "more powerful" if it puts out more power. It uses a higher voltage and higher current from its "more powerful" power source, and it outputs higher voltage into a given antenna impedance (typically 50 ohms).
So, a transmitter that outputs 7V into the 50 ohm antenna is putting out 1 Watt. And if the transmitter is designed to output 225V into the 50 ohm antenna, then it is outputting 1000 Watts.
There is also some amount of gain you can get from the antenna itself. Some antennas can make the ERP (Effective Radiated Power) 2x or more what the transmitter is sending up the feedline.