How does a radio transmitter work? Help with novel?

Question

Hi,

I'm writing a book about an underground army and wanted them to be able to use radio transmitters in order to communicate with other divisions of their army that are situated across the globe. The problem is that I don't really understand how radio transmitters work and can't find an explanation online that explains it in a way that an idiot can understand (hee hee). I need to know a few things:

1) Can a radio transmitter be used in the desert?

2) would it's signal be strong enough to reach around the world?

3) Would my army have to tune their radios into the same frequency or would each division have it's own frequency?

Please help me if you can
Thanks in advance

Answer 1

1) A radio transmitter can definitely be used in the desert. Transmitters will work just about anywhere but under water



2) Yes. Even extremely weak signals can be detected, given suitable equipment. Whether or not the intended receiver is capable of detecting a weak signal and extracting it from all the other noise that abounds in the electromagnetic spectrum may be a different matter. In general, you give the transmitter all the power you can afford to maximize the chance of it being heard. Ham radio operators often challenge each other by using extremely low power transmitters. These low power transmitters are routinely received around the world.



Probably more important is which frequency bands you use. Low frequencies (like AM radio and frequencies in the single digit megahertz) tend to travel very long distances. Higher frequencies often require line-of-sight for adequate communication quality.



3) Typically, individual frequencies are used for a number of reasons, particularly security. If nothing else, think about the log jam of messages if everyone had to use the same frequency. However, each end of a communications link (that is, the transmitter and the receiver) must be using the same frequency.

Answer 2

1 yes . no problem.



2 A short wave transmitter could but it would need quite a large antenna and at least a suitcase size transmitter.However these days global communication is usually via satellite with a transmitter not much larger than a cell phone.



3) they would likely have centralised channels and also division chanels,

Answer 3

1) yes

2) yes, Ham Radio operators and the military do it every day.

3) yes the radios have to be on same frequency



In addition...



Modes of operation

Traditional - SSB (single side band for voice) and CW (Morse Code). Both still used

Modern modes - digital and spread spectrum



See link...

http://en.wikipedia.org/wiki/High_frequency

http://wiki.radioreference.com/index.php/HF_Military_Communications

Answer 4

1. Yes

2. Theoretically yes but in practice no.

3. Either could work.



Try wikipedia.com/numberstations