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CALCULATE AVERAGE POWER TO PEAK POWER

W5LZ said:
Define peak envelope power.
Click to expand...


Peak envelope power = peak voltage x .707, squared, then divided by resistance (which with cb at 1:1 swr would be 50 ohms).

or

(Vp x .707)^2/50 or (Vrms)^2/50 seeing as you love rms so much.


for a 4w cb carrier,peak voltage would be measured at 20v x.707 =14.14v (rms),

14.14v (rms) squared = 199.93v (rms) divided by 50 ohms = 3.998 watts pep,its near enough that you can round up to 4w pep

you'll notice without modulation the carrier is 4w pep or 4w avg,both mean the same in an unmodulated signal.



now when you modulate that carrier to 100%,

peak voltage measured would be 40v as 100% modulation doubles the voltage,

so:

you now have 40v peak x .707 = 28.28v (rms)

28.28v (rms) squared = 799.758v (rms) divided by 50 ohms = 15.995watts (pep),its near enough that you can round up to 16w pep.

you can clearly see when you double peak voltage which is exactly what 100% modulation does you quadruple carrier power.


Hopefully it will sink in now.:headbang:headbang
 
Last edited:
Just incase anyone is interested mod % = sqrt of pep - sqrt of carrier power/ sqrt of carrier power times 100.

so for all you guys out there deadkeying 2w and swinging 40w, your modulation percentage is:

6.324 - 1.414/1.414 x 100

or 347.21% ,not pretty.

for a properly adjusted transmitter it would be

4 - 2/2 x 100 = 100% much nicer to look at on a scope/spectrum analyser or to listen too.
 
Actually my son was allover the first part hes a math freak but hes a bit lost on resistance so that threw him off but the rest he said no problem he said once he learns the resistance and calculations then he said it will be a breeze. I will be happy when they hold there general but Im not going to over push them so they get sick of it or lose interest .

Thanks for all the help !!! Maybe you can in the future enlighten us all on how we can get 500 - 600 watts out of 2 2SC2879 Transistors and to top it off without hitting the saturation point and covering the entire 11 meter or 10 meter band with RF and how that Anartica super duper flux capacitor cooling system works in one of these AM POWER amplifiers because as hard as this is to admit I simply just cant grasp or understand this at all.

I cant seem to grab figure out what Im missing in the construction of some of these Class C amplifiers with SSB switches. I just want my kids to keep moving forward and my son talks of college for radio and electronic repair and if I can get him learn and understand this secret and magical work the one they call the Godfather possesses then my son will also be a worldwide Icon (y)
 
Sorry Tony,

But the godfather of amplitude modulated power is well outwith the talents of this mere mortal,his chryogenic cooling system is well beyond my comprehension,I'm reasonably good at arithmetic,but sadly i failed the exam in bullshitology.

It has to be said though that i don't have access to a helicopter to stress test my amps by dropping them on the viet cong from a great height,nor do i possess the talent to hold up trees whilst leaning on them at an acute 45 degree angle whilst preaching to the world the benefits of my amp building majesty via youtube.Although i must admit "you tube" is a very aptly named medium for the godfathers preaching.

It sort of sums him up.

i realise tube may be a distinctly glaswegian term of endearment so i've included a link to urban dictionary for a definition

http://www.urbandictionary.com/define.php?term=tube&defid=211676

Definitions 2,4,10,11,15,20 would all apply in this case.



TonyV225 said:
Actually my son was allover the first part hes a math freak but hes a bit lost on resistance so that threw him off but the rest he said no problem he said once he learns the resistance and calculations then he said it will be a breeze. I will be happy when they hold there general but Im not going to over push them so they get sick of it or lose interest .

Thanks for all the help !!! Maybe you can in the future enlighten us all on how we can get 500 - 600 watts out of 2 2SC2879 Transistors and to top it off without hitting the saturation point and covering the entire 11 meter or 10 meter band and how that Anartica super duper flux capacitor cooling system works in one of these AM POWER amplifiers because as hard as this is to admit I simply just cant grasp or understand this at all.

I cant seem to grab what Im missing in the construction of some of these Class C amplifiers with SSB switch. I just want my kids to keep moving forward and my son talks of colleg for radio and electronic repair and if I can get him this secret in that the one they call the Godfather possesses then my son will also be a worldwide Icon (y)
Click to expand...
 
Last edited:
jazzsinger,
Your intuition is correct, I was looking for a general definition of peak envelope power.
- 'Doc
 
This formla is kind of cool and makes a person wonder why we all just have to have a True Peak reading meter when we could do the figuring on a damn caculator!!! Does this just prove that most of us are lazy and want that peak power shown to us without the extra work?? LOL!!
 
TonyV225 said:
Actually my son was allover the first part hes a math freak but hes a bit lost on resistance so that threw him off but the rest he said no problem he said once he learns the resistance and calculations then he said it will be a breeze. I will be happy when they hold there general but Im not going to over push them so they get sick of it or lose interest .

Thanks for all the help !!! Maybe you can in the future enlighten us all on how we can get 500 - 600 watts out of 2 2SC2879 Transistors and to top it off without hitting the saturation point and covering the entire 11 meter or 10 meter band with RF and how that Anartica super duper flux capacitor cooling system works in one of these AM POWER amplifiers because as hard as this is to admit I simply just cant grasp or understand this at all.

I cant seem to grab figure out what Im missing in the construction of some of these Class C amplifiers with SSB switches. I just want my kids to keep moving forward and my son talks of college for radio and electronic repair and if I can get him learn and understand this secret and magical work the one they call the Godfather possesses then my son will also be a worldwide Icon (y)
Click to expand...

Adam is doing a class at The University of Ill. so get your money straight.

ampower.jpg
 
moleculo said:
Jazzsinger,

What's with all the CB talk in the Amateur Radio section?
Click to expand...

i would have thought power formula/calculations would be just as relevant in either section,but i could ask the same about all the ham references throughout the cb section,but i realise our hobbies are very closely related and the same theory applies to both.

my references come from what i know best, cb,just like hams in the cb section reference what they know best ,amateur radio,its not meant to upset hams and i'm surprised you ask that question Mole.
 
W5LZ said:
jazzsinger,
Your intuition is correct, I was looking for a general definition of peak envelope power.
- 'Doc
Click to expand...


This any better Doc.?

Peak envelope power of a radio transmitter : The average power supplied to the antenna transmission line by a transmitter during one radio frequency cycle at the crest of the modulation envelope taken under normal operating conditions.

Peak envelope power, PEP

For some applications another form of RF power measurement is required. Called peak envelope power, PEP, it is used to measure the power of some varying waveforms.
There are many instances where a power measurement that takes the peak of the envelope is needed. Many digitally modulated waveforms may require this, and also transmissions such as AM and Single Sideband may also need this type of RF power measurement.
The envelope power is measured by making the averaging time greater than the period of the modulating waveform, i.e. 1/fm where fm is the maximum frequency component of the modulation waveform.
This means that the averaging time of the RF power measurement must fall within a window:

  • It must be large when compared to the period of the highest modulation frequency.
  • It must be small compared to the period of the carrier waveform
The peak envelope power is therefore the peak value obtained using this method.




With PEP measurements, time (sample rate), is a factor and that time "window" is influenced by the highest frequency of the modulating signal source.
 
I could have copied and pasted similar from any one of a number of sources on the net Garth,but felt it better to explain in a practical way,i'm pretty sure that definition should be in Doc's licensing somewhere or at the very least in the many publications of the ARRL or FCC.Why a licensed amateur would have to ask for the definition is beyond me as its freely available from multiple sources.


Captain Kilowatt said:
This any better Doc.?

Peak envelope power of a radio transmitter : The average power supplied to the antenna transmission line by a transmitter during one radio frequency cycle at the crest of the modulation envelope taken under normal operating conditions.

Peak envelope power, PEP

For some applications another form of RF power measurement is required. Called peak envelope power, PEP, it is used to measure the power of some varying waveforms.
There are many instances where a power measurement that takes the peak of the envelope is needed. Many digitally modulated waveforms may require this, and also transmissions such as AM and Single Sideband may also need this type of RF power measurement.
The envelope power is measured by making the averaging time greater than the period of the modulating waveform, i.e. 1/fm where fm is the maximum frequency component of the modulation waveform.
This means that the averaging time of the RF power measurement must fall within a window:

  • It must be large when compared to the period of the highest modulation frequency.
  • It must be small compared to the period of the carrier waveform
The peak envelope power is therefore the peak value obtained using this method.




With PEP measurements, time (sample rate), is a factor and that time "window" is influenced by the highest frequency of the modulating signal source.
Click to expand...
 

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