mx-a 75mhz???
12-27-2005, 03:01 PM
#2
RE: mx-a 75mhz???
AM is amplitude modulation and FM is frequency modulation. You can modulate a frequency by either AM or FM no matter what the frequency is. There are AM and FM systems on the 72MHz frequency also. FM is usually more immune to noise interference than AM. Note that lightning affects AM radio but not FM radio. AM usually has greater range (FM is considered line of sight) but this is not an issue with RC as if you cannot see what you are controlling, there is little need to be able to control it although FM will probably be able to control it also.
George
George
12-27-2005, 03:40 PM
#3
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RE: mx-a 75mhz???
Here are a couple of sample waveforms for AM and FM. In AM the Amplitude is modulated to provide signal data, and in FM, the Frequency is modulated. They both have a carrier wave and the frequency, say 72.950 or 27.095 megahertz is the carrier frequency. This is independent of the type of modulation.
01-12-2006, 05:03 PM
#6
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RE: mx-a 75mhz???
ORIGINAL: ghendrix01
FM is usually more immune to noise interference than AM. ..........AM usually has greater range (FM is considered line of sight) but this is not an issue with RC as if you cannot see what you are controlling, there is little need to be able to control it although FM will probably be able to control it also.
George
FM is usually more immune to noise interference than AM. ..........AM usually has greater range (FM is considered line of sight) but this is not an issue with RC as if you cannot see what you are controlling, there is little need to be able to control it although FM will probably be able to control it also.
George
AM does not have any greater range than FM. Range is based upon transmitter output power and the frequency band that's being used. The 72/75 MHz bands are line of sight, regardless of the type of modulation.
People usualy get this confused because AM radios in their house or automobile have very long ranges, while FM broadcasts do not. It's not a function of the AM or FM modulation, but the frequency involved. AM broacasts are low frequency, around 1.0 MHz (1,000 KHz), and FM broadcasts are at about 100 MHz. The high frequencies are line of sight, and the low ones will bend around the curve of the earth. Also, too, many times the AM broadcast transmitter is putting out many times the output power that an FM broadcaster is putting out.
As far as RC transmitters go, though, you are limited by the design of the transmitter to a range of direct sight, regardless of the band or modulation of your transmitter. If you can't see the model, you can't control it. The manufacturers won't make them any more powerful than that needed to fulfil that purpose.
