Ampliphase
Encyclopedia
Ampliphase is the brand name of an amplitude modulation
Amplitude modulation
Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...

 system achieved by summing phase modulated
Phase modulation
Phase modulation is a form of modulation that represents information as variations in the instantaneous phase of a carrier wave.Unlike its more popular counterpart, frequency modulation , PM is not very widely used for radio transmissions...

 carriers
Carrier wave
In telecommunications, a carrier wave or carrier is a waveform that is modulated with an input signal for the purpose of conveying information. This carrier wave is usually a much higher frequency than the input signal...

. It was originally marketed by RCA for AM broadcast
AM broadcasting
AM broadcasting is the process of radio broadcasting using amplitude modulation. AM was the first method of impressing sound on a radio signal and is still widely used today. Commercial and public AM broadcasting is carried out in the medium wave band world wide, and on long wave and short wave...

 transmitters.

How it works

  1. The system takes a carrier frequency and splits it into two identical signals.
  2. The signals are first phase shifted 135 degrees from each other (to provide a base power output with zero modulation from the transmitter).
  3. Each signal is then phase modulated by the audio signal, one signal is positively phase modulated while the other is negatively phase modulated.
  4. The two signals are then amplified to a desired power.
  5. Finally, the two signals are summed in the final output filter stage of the transmitter.


The result is that when the signals are closer in phase, the output amplitude is larger and when the signals are more out of phase, the output is low.

The Ampliphase system was not developed by RCA, but by McClatchy Broadcasting (a group owner of AM, FM and TV stations, and also a California publisher of newspapers), first at KFBK (AM), Sacramento, CA (50,000 watts), and KOH (AM), Reno, NV (5,000/1,000 watts). Other McClatchy AM stations (KBEE, Modesto, and KMJ, Fresno, both of CA) employed conventional transmitters.

The Ampliphase design, originally proposed by H. Chireix in 1935 and termed "outphasing" by him, was later sold by McClatchy to RCA, which turned it into a mass-produced product, first at the 50,000 watt level, and, later, at the 10,000 and 5,000 watt levels. Unlike most other commercial designs of AM broadcast transmitters Ampliphase units don't require modulation transformer
Modulation transformer
A modulation transformer is an audio-frequency transformer that forms a major part of most AM transmitters. The primary winding of a modulation transformer is fed by an audio amplifier that has about 1/2 of the rated input power of the transmitter's final amplifier stage...

s.

External links

  • Ross Revenge - Transmitter Room - Ampliphase Theory (see Ross Revenge
    Ross Revenge
    The MV Ross Revenge is a radio ship, formerly the home of Radio Caroline, as well as having supported Radio Monique and various religious broadcasters. She was constructed in Bremerhaven in 1960, and initially served as a commercial trawler, notably taking part in the cod wars of the 1970s...

    ).
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK