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Author Topic: 1500 pep output max  (Read 94828 times)
W6RZ
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Posts: 365




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« Reply #90 on: January 16, 2016, 05:36:13 PM »

Easily simulated and hopefully a graphical representation will be helpful. Here's an SSB waveform at an RF frequency of 500 kHz. The first graph is for 1 second of time. It's showing syllables, and the peak at about 0.4 seconds is the first syllable of the word "dedicated".



Next graph is zoomed in 10x. 100 milliseconds of waveform.



Zoom in another 10x. 10 milliseconds of waveform.



Zoom in another 10X. 1 millisecond of waveform.



Zoom in another 5X. 200 microseconds of waveform. At this scale, we're starting to see individual RF cycles, but can still see part of the envelope.



Zoom in another 4X. 50 microseconds of waveform or 25 sine wave cycles at 500 kHz. Same as a CW waveform. The power of 1 cycle (used in the FCC and ITU definition of PEP) is the same as the power over 25 cycles.



The maximum PEP power of the original 1 second waveform is then calculated by taking the maximum RMS value of the voltage waveform, squaring it and dividing by 50 ohms (what WB4JTR is calling "RMS derived power"). That is, ((0.5 * 0.7071) * (0.5 * 0.7071)) / 50 = 2.5 milliwatts.
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WB4JTR
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Posts: 37




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« Reply #91 on: January 16, 2016, 05:40:27 PM »

PEP is power overaged over one RF cycle at the peak of the modulation envelope. In other words, very short-term average power at the peak of the modulation.

Sam

Of course that definition is correct as it is clearly spelled out in the FCC rules for decades now to anyone who takes the time to look it up.

However this cant be defined as RMS power since it simply has not been defined in engineering textbooks, journals, FCC, nor the IEEE....

Carl

I thought we decided not to use the term "RMS power" because it is ambiguous.  "RMS derived" power is a good substitute.

The power in the ITU/FCC definition IS equivalent to RMS derived power.  In fact, the definition of RMS uses the same concept: "Average the squared function (voltage or current in the case of electrical functions) value over the complete cycle, then take the square root."  To derive power from these two numbers (RMS voltage and current) multiply them together.  The result of this procedure is simply the average instantaneous power over one cycle.  Sound familiar?  It's exactly equivalent to the ITU/FCC value for PEP.

You don't need an IEEE reference to this concept.  You can look it up in any basic engineering text.

-Lee

PS:  The W6RZ demo above is correct.  Thanks, OM. Smiley
« Last Edit: January 16, 2016, 05:48:03 PM by WB4JTR » Logged
KM1H
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Posts: 5513




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« Reply #92 on: January 16, 2016, 06:53:17 PM »

Quote
I thought we decided not to use the term "RMS power" because it is ambiguous.  "RMS derived" power is a good substitute.

I dont know who "we" is or when you gave up on trying to force RMS Power on everybody as trying to read all the back and forth gave me a headache.

Quote
The power in the ITU/FCC definition IS equivalent to RMS derived power.  In fact, the definition of RMS uses the same concept: "Average the squared function (voltage or current in the case of electrical functions) value over the complete cycle, then take the square root."  To derive power from these two numbers (RMS voltage and current) multiply them together.  The result of this procedure is simply the average instantaneous power over one cycle.  Sound familiar?  It's exactly equivalent to the ITU/FCC value for PEP.

PEP is an accepted standard, RMS Power or Derived Power is not. It is simply less than a handful on an obscure hobby forum who want to confuse the issue by applying it that way.

Quote
You don't need an IEEE reference to this concept.  You can look it up in any basic engineering text.

Engineering definitions and naming are referred to a standards committee known as the IEEE-SA or arent you aware of that?  I cant find either of your versions even mentioned.

I think this thread should be terminated before it gets out of hand with alternate versions of reality and wasted bandwidth graphs that simply say what was already in the extremely simple and short explanation in the FCC rules for decades which any entry level AC power tech should be able to understand without having to get into unecessary math to make the conversion. I wonder how many of the dumbed down Extra Class era are able to handle it without grabbing for reference material?

Carl
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WB4JTR
Member

Posts: 37




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« Reply #93 on: January 16, 2016, 08:16:44 PM »

Quote
I thought we decided not to use the term "RMS power" because it is ambiguous.  "RMS derived" power is a good substitute.

I dont know who "we" is or when you gave up on trying to force RMS Power on everybody as trying to read all the back and forth gave me a headache.

Quote
The power in the ITU/FCC definition IS equivalent to RMS derived power.  In fact, the definition of RMS uses the same concept: "Average the squared function (voltage or current in the case of electrical functions) value over the complete cycle, then take the square root."  To derive power from these two numbers (RMS voltage and current) multiply them together.  The result of this procedure is simply the average instantaneous power over one cycle.  Sound familiar?  It's exactly equivalent to the ITU/FCC value for PEP.

PEP is an accepted standard, RMS Power or Derived Power is not. It is simply less than a handful on an obscure hobby forum who want to confuse the issue by applying it that way.

Quote
You don't need an IEEE reference to this concept.  You can look it up in any basic engineering text.

Engineering definitions and naming are referred to a standards committee known as the IEEE-SA or arent you aware of that?  I cant find either of your versions even mentioned.

I think this thread should be terminated before it gets out of hand with alternate versions of reality and wasted bandwidth graphs that simply say what was already in the extremely simple and short explanation in the FCC rules for decades which any entry level AC power tech should be able to understand without having to get into unecessary math to make the conversion. I wonder how many of the dumbed down Extra Class era are able to handle it without grabbing for reference material?

Carl

Interesting.  If someone asked you to explain what PEP is and how to compute it, how would YOU derive the power in that cycle as mandated by the ITU/FCC?  Especially if that cycle is not a perfect sinewave (as someone keeps insisting).  And what would you call the result of your derivation to distinguish it from the other derivations of power (instaneous peak, average, etc)?  I like the description "RMS-derived power", but you are free to coin your own descriptive term.  Or go ahead and use "RMS power" -- but be prepared to explain yourself if somebody takes it the wrong way.

I'm sure the reason we don't see the term "RMS power" in the books is because of it's ambiguity (power from RMS data or the RMS value of a set of power data values?).  Unfortunately, it's absence from the literature has not prevented it's common use to refer to power from RMS data.
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W1BR
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Posts: 4195




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« Reply #94 on: January 16, 2016, 08:40:37 PM »

It would seem to me the purity of the RF output relating to being a pure sine wave is entirely dependent on the tank circuit Q.  The tube basically is a switch. The tank Q provides the flywheel effect over the full AC cycle.

Pete
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WB4JTR
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Posts: 37




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« Reply #95 on: January 16, 2016, 08:50:34 PM »

It would seem to me the purity of the RF output relating to being a pure sine wave is entirely dependent on the tank circuit Q.  The tube basically is a switch. The tank Q provides the flywheel effect over the full AC cycle.

Pete

Bingo!
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K6BRN
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Posts: 1339




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« Reply #96 on: January 17, 2016, 12:34:52 AM »

Very strange cult for/against "RMS power" in this thread.  Its like being for/against ... water.  Makes no sense arguing that it does not exist, whether it is a "standard" in the amateur community or not, the terminology is in use in industry and is usually equated with average power.

RMS RF power "measurement" is very common and lots of RF parts exist specifically to do this.  For example, the Linear Technologies LT5587, the Analog Devices ADL5502, the Maxim MAXX2203, and the Hittite HMC1030LP5E all are intended to measure "RF RMS power" - usually as an inline estimator of "Average Power" calculated from measured RMS voltage values.

Regarding books discussing this explicitly, see "Engineering Circuit Analysis" by Hayt and Kemmerly, which is a first year EE text used by almost every accredited program in the USA.  Chapter 11, in my ancient copy.  Plenty of detail on the topic, too.

Not sure where the "Determined Denial" camp is coming from.  Splitting hairs, perhaps, or terminology evangelists?  Makes as much sense as trying to resolve the difference between "flammable" and "inflammable" when there is none, even though there should be.

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SM0AOM
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Posts: 258




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« Reply #97 on: January 17, 2016, 01:11:08 AM »


As far as I know the USA was the first country to adopt p.e.p. as the amateur radio power standard, then other countries followed suit and adopted into their rules. Totally irrelevant to the fundamental purpose of a power limit in the rules of the amateur or any other radio service.

Actually the use of PEP as a metric for amateur radio power limitations was first used in the British GPO rules in the mid/late 50's when SSB was introduced. The GPO limited amateur radio to a maximum of 150 W DC input in their post-war rules, and was not willing to "budge" in this respect.

Proponents of SSB felt that SSB was disadvantaged with respect to AM if this power rule would be used in the future,
so a compromise was worked out.

It resulted in an SSB power limit that was expressed as the PEP output resulting from a 100% modulated carrier from a typical AM transmitter with 150W input. This worked out to 400 W PEP, and stays to this day.

Later changes permitted also other emissions than SSB to use the PEP rating, so CW ultimately got a 6 dB advantage compared to the old 150 W DC input rule.
« Last Edit: January 17, 2016, 02:07:01 AM by SM0AOM » Logged
WB4JTR
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Posts: 37




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« Reply #98 on: January 17, 2016, 05:56:49 AM »

Very strange cult for/against "RMS power" in this thread.  Its like being for/against ... water.  Makes no sense arguing that it does not exist, whether it is a "standard" in the amateur community or not, the terminology is in use in industry and is usually equated with average power.

RMS RF power "measurement" is very common and lots of RF parts exist specifically to do this.  For example, the Linear Technologies LT5587, the Analog Devices ADL5502, the Maxim MAXX2203, and the Hittite HMC1030LP5E all are intended to measure "RF RMS power" - usually as an inline estimator of "Average Power" calculated from measured RMS voltage values.

Regarding books discussing this explicitly, see "Engineering Circuit Analysis" by Hayt and Kemmerly, which is a first year EE text used by almost every accredited program in the USA.  Chapter 11, in my ancient copy.  Plenty of detail on the topic, too.

Not sure where the "Determined Denial" camp is coming from.  Splitting hairs, perhaps, or terminology evangelists?  Makes as much sense as trying to resolve the difference between "flammable" and "inflammable" when there is none, even though there should be.



Thank you BRN.  Well said.

-Lee
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W5HRO
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Posts: 47




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« Reply #99 on: January 17, 2016, 07:26:58 AM »

RMS RF power "measurement" is very common and lots of RF parts exist specifically to do this.  For example, the Linear Technologies LT5587, the Analog Devices ADL5502, the Maxim MAXX2203, and the Hittite HMC1030LP5E all are intended to measure "RF RMS power" - usually as an inline estimator of "Average Power" calculated from measured RMS voltage values.

I work for LTC and yes, we do have a device for measuring true RMS power. RMS power does in fact exist like many don't want to believe and I gave up trying to explain that to the Radiophools on these hams boards, but it's a very complicated measurement method which can still  be done nevertheless. You just won't find RF power meters out there in the mainstream that will do it. Average reading power meters work good enough for the amateur radio and broadcast communities.

As far as the comment that PEP has no shape, that person just blew his entire argument out of the water. The PEP modulation envelope is determined by the audio waveform like the human voice used to modulate the RF or RF supply which creates that envelope. It makes you wonder how that guy ever became a radio engineer.
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W5HRO
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Posts: 47




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« Reply #100 on: January 17, 2016, 07:53:19 AM »

It would seem to me the purity of the RF output relating to being a pure sine wave is entirely dependent on the tank circuit Q.  The tube basically is a switch. The tank Q provides the flywheel effect over the full AC cycle.

Absolutely, that too. I was focused mainly on trying to explain to the guy that most amplifiers hams use operate at a bias point (class) where the shape of PEP envelope will always be slightly distorted anyway and will always contain harmonics so it wont matter. A tube amp if not overdriven will almost always contain some level of even-order harmonics and solid-sate amps odd-order harmonics. The tubes and transistors will do that all by themselves so they are not just a switch. That is true for both audio amps and RF amps.

Now, with RF tuned circuits those harmonics will be attenuated some, it just depends on how much and those circuits can also distort the shape of the modulated PEP envelope further, but that’s another topic.


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WB4SPT
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Posts: 782




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« Reply #101 on: January 17, 2016, 08:02:57 AM »

Since we can't collectively converge on a solution for power, perhaps we try to talk voltage limits instead.  I'll submit we limit our stations to 386 Volts peak into a 50 Ohm load.   Roll Eyes
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WB4JTR
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Posts: 37




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« Reply #102 on: January 17, 2016, 08:11:10 AM »

RMS RF power "measurement" is very common and lots of RF parts exist specifically to do this.  For example, the Linear Technologies LT5587, the Analog Devices ADL5502, the Maxim MAXX2203, and the Hittite HMC1030LP5E all are intended to measure "RF RMS power" - usually as an inline estimator of "Average Power" calculated from measured RMS voltage values.

I work for LTC and yes, we do have a device for measuring true RMS power. RMS power does in fact exist like many don't want to believe and I gave up trying to explain that to the Radiophools on these hams boards, but it's a very complicated measurement method which can still  be done nevertheless. You just won't find RF power meters out there in the mainstream that will do it. Average reading power meters work good enough for the amateur radio and broadcast communities.

As far as the comment that PEP has no shape, that person just blew his entire argument out of the water. The PEP modulation envelope is determined by the audio waveform like the human voice used to modulate the RF or RF supply which creates that envelope. It makes you wonder how that guy ever became a radio engineer.

(sigh)... Check your definition of scalar quantity.  That's what PEP is.  No shape allowed.

To W6RZ:  Thanks again for the simulation.  It clearly demonstrates the difference in time scale of the PEP definition and any property of the audio or envelope wave forms.  I mentioned this early in the "discussion".  That's what makes PEP independent of envelope waveform, and why the CW PEP of those 25 cycles is the same as the voice waveform as you demonstrated.

These concepts are indeed what "any entry level AC power tech should learn".

« Last Edit: January 17, 2016, 10:38:32 AM by WB4JTR » Logged
W5HRO
Member

Posts: 47




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« Reply #103 on: January 17, 2016, 09:03:53 AM »

(sigh)... Check your definition of scalar quantity.  That's what PEP is.  No shape allowed.

Quit quoting those FCC and ITU specs. That's where your confusion is coming from; they are not valid with voice communications or music. The descriptions only work for CW and any other mode that only involves a transmitted carrier that is not modulated by intelligence unless it's a single tone at constant level and frequency. The descriptions are not valid for SSB or AM.

These concepts are indeed what "any entry level AC power tech should learn".

The problem with many amateur radio people or people with strictly RF backgrounds is that they usually have a very narrow focus and area of expertise. So narrow that they tend to call anything outside of that narrow focus nonsense and it's usually just due to their own ignorance. When they don't understand something they resort to quoting something in a published document instead, even it has limitations or is some cases is not even valid to the discussion.
« Last Edit: January 17, 2016, 09:47:12 AM by W5HRO » Logged

K4KYV
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Posts: 116




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« Reply #104 on: January 17, 2016, 09:50:40 AM »

RMS power does in fact exist like many don't want to believe and I gave up trying to explain that to the Radiophools on these hams boards, but it's a very complicated measurement method which can still  be done nevertheless. You just won't find RF power meters out there in the mainstream that will do it. Average reading power meters work good enough for the amateur radio and broadcast communities.

Please explain exactly what is the difference between this alleged "RMS power", and average (aka mean) power? Can you cite a reputable engineering text that gives a definition of "RMS power"?

Yes, this is more than mere semantics. In the field of science and engineering, language must be precise.  There is no place for sloppy definitions, mythology or pseudo-science.

Regarding the amateur power limit, this thread perfectly exemplifies the FCC's folly in a one-size-fits-all p.e.p. power limit.  Few of to-day's licensed amateurs understand or could correctly explain exactly what p.e.p. is, let alone accurately measure it, particularly when feeding a typical real-world amateur radio antenna.  The FCC admitted as much when they adopted the rule.  Under the old (DC input) power rule, amateur transmitters running at 90% or more of the legal limit were required to possess the necessary instruments to accurately measure transmitter power. Such a requirement was deleted under the new standard. In the proposal and R&O (to paraphrase) the FCC stated that amateurs wouldn't be required to actually measure transmitter power, only to comply with the limit, and in event of a station inspection the FCC agent would take care of the measuring.  Then they went on to say that amateurs have "means other than accurate measurement" to determine transmitter power, whatever that is supposed to mean.

Some make a big hullabaloo over the limit on p.e.p. and whether or not an errant voice peak might happen to "peek" a little above the magic number, yet another provision of the power limit rule is routinely ignored without second thought, the one at the very top of the list:

§97.313   Transmitter power standards.
(a) An amateur station must use the minimum transmitter power necessary to carry out the desired communications.
« Last Edit: January 17, 2016, 09:52:58 AM by K4KYV » Logged
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