AM?

simple really

whats the differnce between AM and FM? is something to do with VHF and UHF

AM - amplitude modulation
FM - frequency modulation

Its down to the way the signal is generated... I think...

*whistles until someone clever comes a long*

simle version:

am: uses a varying amlitude to send the signal
fm: sends the signal by altering the frequency.

FM is less affected by interference than AM, so generally youll get a much clearer signal. FM requires a more complicated transmitter and receiver, so AM tends to be used for very cheap equipment.

VHF and UHF are just names for bits of the radio spectrum, and are not related to the modulation system used.

AM: you have a carrier wave of a much higher frequency than what you intend to transmit. You vary the amplitude of that carrier wave so that it matches the profile of the wave to be transmitted. Its fairly simple to make such a tranmitter. Recieving it, like receiving anything to do with radiowaves, is witchcraft, and to be avoided at all costs by anyone who values their sanity.

FM:..... yeah. Same kinda thing but you vary the frequency of the carrier instead of the amplitude.

Receiving an AM signal isnt difficult.... a coil of wire, capacitor, and diode is all you need. If you want you can do extra tricks to concentrate more precisely on the wavelength you want.

You can even pick up AM radio by accident, I had some computer speakers which picked up a faint French radio station if you left them switched on and turned up without the computer on.

Heres a good analogy...

A trumpeter can send you a Morse code message in two ways. He can play a note for each dot or dash and vary the loudness, playing a soft note for a dot, and a loud note for a dash. If there is nothing to confuse the sound you could hear it at the other end of a house. Another trumpeter can send a different message by playing a different note and making it louder and softer, and with a wee bit of difficulty you can listen to the right note to make out the message.

If, however, people are opening and closing doors all the time it becomes very difficult to make out whether any one note is louder or softer and the message, even when it doesnt become inaudible, can get hidden. And it doesnt take a lot of some other noise, such as a violin being played badly, to confuse your ear and make it impossible to pick out the message.

Alternatively the first trumpeter can use notes of different pitches, one for dot and one for dash. A second trumpeter would have to choose two notes that are both higher up the scale to avoid confusion, but again it would be possible to make out the message despite the second player. Whats more, doors being opened and closed between you and the trumpeter would make the signal hard to hear, but wouldnt hide the actual message short of making it inaudible - the signal is less vulnerable to interference. Also, the violinist would have to work harder to distract the ear from the two-tone warbling of the trumpet.

Best advice is to stop paying for the kids music lessons and get some peace and quiet!

Great annalogy (mispell?) Rich

Another way to compare AM & FM is when listening to the radio ...although most forum members are younger than me so wont remember medium wave.


Basically Radio 1 used to be (if I remember right) on 247mhz MW and Radio Luxenbourg was definately on 208 MW both these were prone to huge reception difficulties depending on the time of day.

I am sure I am not the only one to listen to Luxenbourg with a tranny under my pillow and hear it constantly fading in and out.

So this is the difference..AM ...at the time available to a HUGE audience but rubbish quality....FM superb non fade ...and the previosly unheard of STEREO...all this is Grandad Speak to most in a DAB audio age!

So anyway ...this is what an AM radio set is like...it works... and is ok if you want a pile of old technology..FM is not new ...I have a Skyleader FM radio set I use im my model aircraft that is 22 years old, and i will bet the technology in RC is older than that!

I would advise against any AM set in Roboteering...even for ants.

Tom

Erm. Maybe youre right... No Ive just checked... analogy is correct! :proud:

I Meant I thought I may be spelling it wrong Rich I had just returned from a few birthday drinks so forgot you had used the same word at the start of the post:)

Tom

:)

Richard, when are we going to see you at another event? Its a long time since I last saw you.

And why dont you put yourself up for FRA chairman?

Mike.

It has been a while! I had an unlucky year, every event that was within distance I was too unwell for or family commitments kept me away! I will be at Debenham, I WILL be!

Erm... Work? Organise people? Hmmm. If I could get myself organised, maybe. :)