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AVG versus PEP?
- Thread starter steved
- Start date
AVG is usually when people refer to the reading on a BIRD or similar meter.
(AVERAGE = AVG)
people claim the only way to measure AM output is true PEP (peak envelope power).
a BIRD 43 meter will read average power.. it was designed to read CW (constant wave aka carrier aka deadkey)
you can get a kit for the bird meter to read true peak power or buy a bird 43p with the peak kit already in it.
most cheap watt meters will read PEP or PEAK watts..
they are very inaccurate and 99% of the time, not even close.
unless the meter has a built in powered circuit to calculate true peak power the readings are pretty much useless..
some have a setting for AVG or AVERAGE and sometimes they are pretty damn close to what a bird will show!
you can have 2 radios that show identical PEP output and when you put
them on a bird one will swing forward quite a bit and the other might not
swing forward much at all or swing backwards!
if you hook both of those radios to an amplifier and check current consumption..
the radio that shows a higher average reading will cause the amplifier to draw more current..
as for watt being frequency, the only way to determine that is by hooking
the radio up to a spectrum analyser. this piece of equipment is very
expensive and not too many cb shops have one (or care anyway)
im sure someone else will come along and clarify/correct what i said :wub:
A 'watt' is a measurement of the amount of work being done. Electrically, it's defined as the amount of work being done by 1 volt with 1 ampere of current flowing.
If you have a circuit that is flowing 1 amp at 1 volt then the work/power being done is 1 watt.
The difference between an 'average' watt and a 'Pep' watt is in how 'fast' you are doing the measuring, or, how much the work varies in a unit of time. For instance. A constant carrier signal is just that, constant. Doesn't vary in magnitude. ('Dead key') But, when you modulate that constant carrier, put an audio signal on it, then the amplitude of the signal changes with the frequency of the applied signal (voice/tone/whatever). If you happen to do the measuring at a voice/tone peak, it will be more watts than if you measure it during a tone/voice 'minimum' {a voice can be considered an AC signal since the tone varies according to how fast (frequency) the vocal cords are vibrating (oscillating)}. An 'average' watt meter sort of averages those peaks/valleys over a period of time longer than the time for one full cycle of that voice 'oscillation'. That's because of the way a typical mechanical meter works, it isn't very fast moving, takes time for that current flowing in the meter to make the needle do any moving. [Sheesh, getting sort of involved, huh?]
When you consider an electrical circuit you are usually only interested in the maximums. That way you can design the circuit so that it's strong enough to handle that much power, sort of. Or you want to know what the maximum power is, right? So, all them 'low' spots don't really interest you. So, you design a meter that only reads the maximum values, only reads the "peaks" of the signal, and ... ... "TA-DA!" ... you got a 'Pep' meter. The same amount of power is being produced or transmitted. The only difference is in how, or "where" in the cycle of that transmitted signal the measurement is taken. An average meter and a Pep meter show different readings for the exact same watt that's coming out of the transmitter (or amplifier). The only practical difference between the two is the 'size' of the number. There is a definite relationship between those two numbers, average watt and Pep watt. If you know what that relationship is, you can calculate one from the other. (A pep watt is about 1.4 times the 'size' of an average watt. So 100 average watts is about 140 Pep watts.) Why use an averaging meter instead of a Pep meter? Because that's what you happen to have. What happens if you use a Pep meter to read a constant or continuous signal, no variations from applied modulation? You get the same reading as the averaging meter gives (or should), since there's no peaks and valleys, or it's all peaks, whatever. The confusion comes in because people seem to think that a watt changes in size. It doesn't. Only in how it's measured.
That's all a generalization. Nothing absolutely 'exact', but close enough for government standards, sort of.
- 'Doc
((If you are after 'bigger' numbers, just lie about it. Much cheaper/easier than not.))
Oh, one last thing. I'm on my first cup of coffee. If the numbers are wrong it's because it's my first cup of coffee. If I check it later I may change or correct it.. if I remember. The general idea is true, the rest is subject to more coffee.
If you have a circuit that is flowing 1 amp at 1 volt then the work/power being done is 1 watt.
The difference between an 'average' watt and a 'Pep' watt is in how 'fast' you are doing the measuring, or, how much the work varies in a unit of time. For instance. A constant carrier signal is just that, constant. Doesn't vary in magnitude. ('Dead key') But, when you modulate that constant carrier, put an audio signal on it, then the amplitude of the signal changes with the frequency of the applied signal (voice/tone/whatever). If you happen to do the measuring at a voice/tone peak, it will be more watts than if you measure it during a tone/voice 'minimum' {a voice can be considered an AC signal since the tone varies according to how fast (frequency) the vocal cords are vibrating (oscillating)}. An 'average' watt meter sort of averages those peaks/valleys over a period of time longer than the time for one full cycle of that voice 'oscillation'. That's because of the way a typical mechanical meter works, it isn't very fast moving, takes time for that current flowing in the meter to make the needle do any moving. [Sheesh, getting sort of involved, huh?]
When you consider an electrical circuit you are usually only interested in the maximums. That way you can design the circuit so that it's strong enough to handle that much power, sort of. Or you want to know what the maximum power is, right? So, all them 'low' spots don't really interest you. So, you design a meter that only reads the maximum values, only reads the "peaks" of the signal, and ... ... "TA-DA!" ... you got a 'Pep' meter. The same amount of power is being produced or transmitted. The only difference is in how, or "where" in the cycle of that transmitted signal the measurement is taken. An average meter and a Pep meter show different readings for the exact same watt that's coming out of the transmitter (or amplifier). The only practical difference between the two is the 'size' of the number. There is a definite relationship between those two numbers, average watt and Pep watt. If you know what that relationship is, you can calculate one from the other. (A pep watt is about 1.4 times the 'size' of an average watt. So 100 average watts is about 140 Pep watts.) Why use an averaging meter instead of a Pep meter? Because that's what you happen to have. What happens if you use a Pep meter to read a constant or continuous signal, no variations from applied modulation? You get the same reading as the averaging meter gives (or should), since there's no peaks and valleys, or it's all peaks, whatever. The confusion comes in because people seem to think that a watt changes in size. It doesn't. Only in how it's measured.
That's all a generalization. Nothing absolutely 'exact', but close enough for government standards, sort of.
- 'Doc
((If you are after 'bigger' numbers, just lie about it. Much cheaper/easier than not.))
Oh, one last thing. I'm on my first cup of coffee. If the numbers are wrong it's because it's my first cup of coffee. If I check it later I may change or correct it.. if I remember. The general idea is true, the rest is subject to more coffee.
@%100 modulation your resting carrier should rise to approximately 1 and 1/2 times the resting carrier, so 100 watts should go from a resting carrier of 100 watts to 150 watts pep.
"as for watt being frequency, the only way to determine that is by hooking the radio up to a spectrum analyser."
wrong. observe the manufacturers maximum output specification for the number and type of devices used (transmitter or amplifier) and don't worry about it.
"A pep watt is about 1.4 times the 'size' of an average watt. So 100 average watts is about 140 Pep watts."
wrong.
"@%100 modulation your resting carrier should rise to approximately 1 and 1/2 times the resting carrier, so 100 watts should go from a resting carrier of 100 watts to 150 watts pep"
wrong.
when measuring AVG the increase in power above the resting unmodulated carrier with a modulation index of 100% is 1.76db.. 100W + 1.76db. = 150W. the peak-to-carrier ratio is 1.5:1.
dB = 10 LOG(1 + (M2 / 2) )
when measuring PEP the increase in power above the resting unmodulated carrier with a modulation index of 100% is 6db.. 100W + 6db. = 400W. the peak-to-carrier ratio is 4:1.
dB = 10 LOG(1 + M)2
4 / 1.5 = 2.66
AVG = PEP / 2.66
PEP = AVG X 2.66
http://www.firecommunications.com/hlsos.html
wrong. observe the manufacturers maximum output specification for the number and type of devices used (transmitter or amplifier) and don't worry about it.
"A pep watt is about 1.4 times the 'size' of an average watt. So 100 average watts is about 140 Pep watts."
wrong.
"@%100 modulation your resting carrier should rise to approximately 1 and 1/2 times the resting carrier, so 100 watts should go from a resting carrier of 100 watts to 150 watts pep"
wrong.
when measuring AVG the increase in power above the resting unmodulated carrier with a modulation index of 100% is 1.76db.. 100W + 1.76db. = 150W. the peak-to-carrier ratio is 1.5:1.
dB = 10 LOG(1 + (M2 / 2) )
when measuring PEP the increase in power above the resting unmodulated carrier with a modulation index of 100% is 6db.. 100W + 6db. = 400W. the peak-to-carrier ratio is 4:1.
dB = 10 LOG(1 + M)2
4 / 1.5 = 2.66
AVG = PEP / 2.66
PEP = AVG X 2.66
http://www.firecommunications.com/hlsos.html
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So you're gonna argue about 10 watts which is what most meters claim as thier accuracy? PLEASE!
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" So 100 average watts is about 140 Pep watts"
the above statement is wrong, for the second time. furthermore meter accuracy is not specified in power but in a percentage of error for total power measured referenced to center scale.
remember this?
PEP = AVG X 2.66
100WAVG = 266WPEP
now if you're still able to follow along we're talking about a difference of 126W.
reread my previous post until you get it.
the above statement is wrong, for the second time. furthermore meter accuracy is not specified in power but in a percentage of error for total power measured referenced to center scale.
remember this?
PEP = AVG X 2.66
100WAVG = 266WPEP
now if you're still able to follow along we're talking about a difference of 126W.
reread my previous post until you get it.
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freecell;109729 [F said:
Wrong. Meter accuracy is specified as a percentage of FSD (Full Scale Deflection) or ESD (End Scale Deflection).
"What's the difference between a AVG watt and a PEP watt?"
TIME. the answer is in the question.
"Does one or the other actually represent the watts staying on frequency?"
NO.
AVG measurement represents a sampling of power levels from trough to trough for one cycle of the envelope, from trough to crest and back to the next trough. for example, if power is measured at every degree (360) from one trough to the next and then the power levels at each instant in time for all 360 measurements were added and divided by 360 this yields average power. PEP measurement looks at maximum power produced at a single instant in time at the crest of the pattern only. both measurements are valid, only the time domain differs. while according to some the preferred measurement method may be AVG but what's interesting is that most of the popular hf devices (2290, 2879, etc.) are rated by the manufacturers in PEP output. duh!
"Meter accuracy is specified as a percentage of FSD (Full Scale Deflection) or ESD (End Scale Deflection)."
while this is true for the higher end equipment, CS was used by Dosy and others though no spec is currently mentioned in the user manuals. it appears in older versions of the documentation.
TIME. the answer is in the question.
"Does one or the other actually represent the watts staying on frequency?"
NO.
AVG measurement represents a sampling of power levels from trough to trough for one cycle of the envelope, from trough to crest and back to the next trough. for example, if power is measured at every degree (360) from one trough to the next and then the power levels at each instant in time for all 360 measurements were added and divided by 360 this yields average power. PEP measurement looks at maximum power produced at a single instant in time at the crest of the pattern only. both measurements are valid, only the time domain differs. while according to some the preferred measurement method may be AVG but what's interesting is that most of the popular hf devices (2290, 2879, etc.) are rated by the manufacturers in PEP output. duh!
"Meter accuracy is specified as a percentage of FSD (Full Scale Deflection) or ESD (End Scale Deflection)."
while this is true for the higher end equipment, CS was used by Dosy and others though no spec is currently mentioned in the user manuals. it appears in older versions of the documentation.
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my goodness ! we can only hope they ain't whistling Dixie into them there microphones :drool: Show me those peppy all peppered up numbers. I'd bet to say most Cb'ers wouldn't want to handle the true truth of what was really going on . So AVG watts to Peppy watts ? however it's explained , peppy was sell ! weather the truth or not. Now my next question would be this .....What's the differents between AVG watts and RMS watts ? are these the same ?
RMS stands for "Root Mean Square", which is fancy mathematical formula for finding the average amount of power an amplifier can continuously produce. There is no legal standard for calculating RMS watts for an amplifier. Most amplifier makers get a "UL" Rating from the Underwriters Labratories to obtain the most 'true' RMS rating.
Since most amps sound their best when they are 'cranked', some musicians look at the Peak wattage more than the RMS rating. Also, tube-amplifiers are usually not rated by RMS.
IM not answering my own question here am I ?
Since most amps sound their best when they are 'cranked', some musicians look at the Peak wattage more than the RMS rating. Also, tube-amplifiers are usually not rated by RMS.
IM not answering my own question here am I ?
Sorry I had my pep and the fictional RMS readings switched around but you have to admit pep is the only true measurement of an amplitude modulated signal, correct?
here it is again from almost 4 years ago........
http://www.worldwidedx.com/showthread.php?p=17073&highlight=Root+Square#post17073
"but you have to admit pep is the only true measurement of an amplitude modulated signal, correct?"
now you're beginning to get it. remember, ssb and dsb are also forms of amplitude modulated signals.
http://www.worldwidedx.com/showthread.php?p=17073&highlight=Root+Square#post17073
"but you have to admit pep is the only true measurement of an amplitude modulated signal, correct?"
now you're beginning to get it. remember, ssb and dsb are also forms of amplitude modulated signals.
Generally, the reason for specifying center scale for anything is to help prevent damage to the meter movement. The Navy still tells EMs and ETs to select a meter scale (analog) that puts the needle in the middle third of the scale. They admit that it's a compromise between documented accuracy and meter damage, such as might happen when the EM/ET selects too low a range and the needle bounces off the right hand stop. I suspect Dosy and the others of that sort used the same good logic.
In any case, that particular Dosy or other meter, if delivered to a calibration lab, would be calibrated at FULL SCALE, using the voltage or current value provided by the manufacturer. The maximum accuracy of any analog meter will be at the end scale/full scale value.