Ampliphase is the brand name of an amplitude modulation system achieved by summing phase modulated carriers. This modulation and amplifier technology family was originally marketed by RCA for AM broadcast transmitters. The Ampliphase system was not developed by RCA, but by McClatchy Broadcasting in the mid-1930s. McClatchy Broadcasting acquired the technology via patent acquisition. The Ampliphase design was originally proposed by H. Chireix in 1935 and termed "Outphasing" by him. He sold the patent to McClatchy Broadcasting that later sold the patent to RCA. RCA turned "Outphasing" transmitters into a mass-produced product. RCA's first transmitters using this modulation system were at the 50,000 watt level but later lower power transmitters such as 10 kw and 5 kw were made. McClatchy Broadcasting was a former group owner of AM, FM and TV stations as well as a California publisher of newspapers. McClatchy Broadcasting should not be confused with the present-day McClatchey Broadcasting LLC, a different corporate entity. Only one known transmitter of this type is still in use. KFBK in California maintains an RCA BTA-50H (the "last gasp" of the Ampliphase concept) as an auxiliary transmitter. Radio Caroline has a working RCA BTA-50H on display aboard its radio ship Ross Revenge, however this transmitter has fallen out of use and is unlikely to be put back on the air since the Ross Revenge currently broadcasts via relay to a more efficient land-based transmitter. How it works The system takes a carrier signal and splits it into two identical signals. The signals are first phase shifted 135 degrees from each other (to provide a base power output with zero modulation from the transmitter). Each signal is then phase modulated by the audio signal: one signal is positively phase modulated while the other is negatively phase modulated. The two signals are then amplified to a desired power. 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 lower. A complication is the necessity for a "drive regulator", which implementation is quite simple at 10 kW or lower levels, but is more complicated at higher levels. "Drive regulation" is most effective when the instantaneous power output approaches zero. Development The Ampliphase system was not developed by RCA, but by McClatchy Broadcasting