Editing Peak envelope power

{{Short description|Measure of radio transmission power}}
[[File:Peak_Envelope_Power.svg|thumb|right|Representation of the peak envelope power (PEP) using the example of an AM-modulated signal. The PEP is the power area shown in red.]]
'''Peak envelope power''' (PEP) is the average power over a single [[radio frequency]] cycle at the crest of the [[modulation]]. PEP is normally considered the power output at the occasional or continuously repeating crest of the modulation envelope under normal operating conditions. Many regulatory authorities use PEP to set maximum power standards for radio transmitters.<ref>R. Dean Straw, ed. ''ARRL Handbook For Radio Amateurs''. Newington, Connecticut: American Radio Relay League, 1999, p. 6.7</ref>

==AM PEP==
Assuming linear, perfectly symmetrical, 100% modulation of a carrier, PEP output of an [[amplitude modulation|AM]] transmitter is four times its [[carrier wave|carrier]] PEP; in other words, a typical modern 100-watt amateur transceiver is usually rated for no more than, and often less than, 25 watts carrier output when operating in AM.<ref>R. Dean Straw, ed. ''ARRL Handbook For Radio Amateurs''. Newington, Connecticut: American Radio Relay League, 1999, p. 15.6</ref> 

==PEP vs. average power==
PEP is equal to steady carrier power, or [[Wireless telegraphy|radiotelegraph]] dot or dash average power, in a properly-formed [[Continuous wave|CW]] transmission. PEP is also equal to average power in a steady [[Frequency modulation|FM]], [[Frequency-shift keying|FSK]], or [[Radioteletype|RTTY]] transmission. 

Although average power is the same as PEP for complex modulation forms, such as [[Frequency Shift Keying|FSK]], the peak envelope power bears no particular ratio or mathematical relationship to longer-term average power in distorted envelopes, such as a [[Continuous wave|CW]] waveform with power overshoot, or with [[amplitude modulation|amplitude modulated]] waveforms, such as SSB or AM voice transmissions. Typical average power of a SSB voice transmission, for example, is 10-20% of PEP. The percentage of longer term average power to PEP increases with processing, and commonly reaches ~50% with extreme speech processing.

==PEP level control==
Most modern amateur transceivers sample PEP to adjust power, using an ALC (automatic level control) system. Time delay in the ALC system and finite time of RF signals passing through multiple stages, in particular narrow filters, often gives rise to unusual envelope distortion. This distortion commonly appears as envelope power overshoot on leading edges, and sometimes causes negative carrier shift on AM. Some more poorly designed transceivers have a short term envelope power overshoot several times the steady-state PEP setting. This envelope overshoot further complicates definitions of PEP and average power.                     

PEP was often used in non-[[Broadcasting|broadcast]] AM applications because it most accurately described the potential of mobile transmitters to interfere with each other.  Its use is now somewhat [[deprecated]], with the ''average'' [[transmitter power output]] (or sometimes ''average'' [[effective radiated power]]) now typically being preferred.

==References==
{{Reflist}}

==See also==
*[[Federal Standard 1037C]]

{{DEFAULTSORT:Peak Envelope Power}}
[[Category:Radio transmission power]]