Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: Prev 1 2 3 4 [5] 6 7 8 9 10 ... 22 Next   Go Down
  Print  
Author Topic: 1500 pep output max  (Read 94964 times)
WB4JTR
Member

Posts: 37




Ignore
« Reply #60 on: January 11, 2016, 05:55:03 PM »

Audiophool version of reality based on waveform shape has no place in RF linear amplifiers.  RF power is always expressed as RMS [ed- "RMS based"] because the [RF] waveform is always sinusoidal.  The FCC demands it by limiting harmonic content.  So PEP is simply RMS [ed- "RMS based"] power in the single highest-amplitude sinusoid contained within the signal envelope.
« Last Edit: January 20, 2016, 03:03:21 PM by WB4JTR » Logged
KM1H
Member

Posts: 5570




Ignore
« Reply #61 on: January 12, 2016, 12:01:07 PM »

Wow! You probably believe the earth is flat also.

How about coming up with the FCC citation to support your "theory"?
Logged
KM3F
Member

Posts: 910




Ignore
« Reply #62 on: January 12, 2016, 04:01:10 PM »

Visit this web  address            www.eznec.com/Amateur/RMS_Power.pdf.
There you will find that RMS power can be calculated as a Math function only, and has no use or value in terms of RF POWER.
Be sure you keep repeating wave forms separate from random waveforms such as voice because they must be treated differently in terms of RF power.
A random wave form such as voice modulation cannot be practically represented by anything more the  Peak values or Average values, for power into a Load.
This is why good RF power meters offer Peak and average functions.
Look at the pdf to find out why.

Good luck..
Logged
W5HRO
Member

Posts: 47




Ignore
« Reply #63 on: January 13, 2016, 05:40:04 PM »

Looks like another one of those Extra Class CB'ers  Roll Eyes  They are all over...
Logged

K4KYV
Member

Posts: 116




Ignore
« Reply #64 on: January 13, 2016, 08:17:48 PM »

There is no such thing as "RMS power".  Average or mean power is what you get when you multiply RMS voltage times RMS current. Average voltage times average current results in a physically meaningless quantity. Nevertheless the term RMS power is widely but incorrectly used within the audiophool community.

Even the term "average voltage" and "average current" must be qualified.  The average voltage or current value of a sine wave or any other unrectified a.c. waveform is inherently zero, since one half cycle is positive with respect to base line while the other half cycle is negative.  A precise description would be the average (or mean) of the absolute value of  voltage or current of the a.c. waveform.
Logged
K4KYV
Member

Posts: 116




Ignore
« Reply #65 on: January 14, 2016, 07:24:10 AM »

Popular Hammy Hambone "wattmeters", including the highly extolled Bird 43, don't measure power at all; they are RF voltmeters, with a scale calibrated to read watts into an accurately-known purely resistive load. Using a diode to rectify the RF, they feed the rectified voltage a DC meter, reading absolute-value based average voltage, not true RMS. With a steady carrier source like FM or key-down CW they read correctly, but with a varying-amplitude signal like AM, SSB, pulse and certain digital modes, average voltage is not the same as RMS, and the meter tends to read low. That's why a Bird 43 set to read average power indicates so little power with SSB.  The most widely available true-RMS reading instrument is the thermocouple RF ammeter, but those are very sluggish and don't respond well to rapid peaks. So-called "peak reading" wattmeters are merely average-reading diode rectifier voltmeters with an electronic "hang" circuit, to hold short RF voltage peaks long enough to produce a meter indication. Even those are of questionable accuracy, since they may not fully capture every short-duration peak.  Peak readings can be observed with good accuracy using a calibrated oscilloscope set to monitor the RF envelope pattern.

That was one problem the FCC cited for not using average or mean power as the standard for legal limit.  But to-day, true RMS-reading rf voltage sensors and therefore true average power reading meters are available. These are still diode-rectifier RF voltmeters but which use more complex electronics than the simple hang circuit used for peak readings.  One example is the Bird APM-16 average-reading power meter described here:

http://www.birdrf.com/Products/Wattmeters_Line%20Sections/PortableWattmeters/APM-16_Average-Reading-Power-Meter.aspx

The manual for the APM-16 can be viewed at
http://www.repeater-builder.com/test-equipment/bird/pdf/bird-apm16-im.pdf
Logged
WB4JTR
Member

Posts: 37




Ignore
« Reply #66 on: January 14, 2016, 09:05:02 AM »

Wow! You probably believe the earth is flat also.

How about coming up with the FCC citation to support your "theory"?

The ITU citation was posted in message #29:
1.157  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.

Notice it is based on one sinusoidal cycle as I stated.

A more accurate term for the often-used "RMS power" would be "RMS-derived power".  But that's a little harder to say.  What is being referenced is just "power", a calculation of work per unit time.

The auxiophools have their own loose definition of "RMS" power which we can safely ignore. My post was in response to message #14 that asserted RMS-derived power of a single tone SSB signal is 3dB less than PEP. A truly nonsense idea.

Taken literally, RMS power CAN exist but it is part of a statistical calculation of standard deviation of power over a period of time. [ed- This is the more obscure interpretation.]
« Last Edit: January 18, 2016, 07:36:32 PM by WB4JTR » Logged
W5HRO
Member

Posts: 47




Ignore
« Reply #67 on: January 14, 2016, 12:37:58 PM »

Taken literally, RMS power CAN exist but it is part of a statistical calculation of standard deviation of power over a period of time.

That's the only thing so far you have said that makes any sense. If you go back and read your post though that Carl responded to it's up in the stratosphere and makes no sense at all. The FCC and harmonic part is completely insane. That ITU citation is also badly worded. Average power and peak envelope power are NOT the same thing at all. They should remove the word "average" from the sentence.

Anyway, a lot of people including myself consider average or mean power just RMS power. Many of the old cheap power meters had those scales labeled as RMS. The problem is some just like to get really nit-picky on technical terms and definitions. It just like the majority of all hams pronounce GHz as Giga-Hertz when it’s is really pronounced Jiga-Hertz with a J. How many people do you ever hear pronounce GHz that way though? Almost none, right? That doesn't mean I'm going to come into a topic or QSO whenever I hear it pronounced Giga-Hertz and say “Hey, you are pronouncing GHz wrong”.

What’s important is that RMS power should never be confused with PEP. Average power and peak envelope power should never be considered as the same thing.

73’s
« Last Edit: January 14, 2016, 02:47:34 PM by W5HRO » Logged

KM1H
Member

Posts: 5570




Ignore
« Reply #68 on: January 14, 2016, 02:26:55 PM »

Wow! You probably believe the earth is flat also.

How about coming up with the FCC citation to support your "theory"?

Quote
The ITU citation was posted in message #29:
1.157  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.


Youre not even intelligent enough to read, no wonder Ten Tec is down the tubes and the few I owned were pure junk....
https://www.qrz.com/lookup

From that same Post 29

Quote
Note that there are no references to "RMS Power" here, nor in any radio engineering texts.

Carl
Logged
WB4JTR
Member

Posts: 37




Ignore
« Reply #69 on: January 14, 2016, 04:02:21 PM »

Taken literally, RMS power CAN exist but it is part of a statistical calculation of standard deviation of power over a period of time.

That's the only thing so far you have said that makes any sense. If you go back and read your post though that Carl responded to it's up in the stratosphere and makes no sense at all. The FCC and harmonic part is completely insane. That ITU citation is also badly worded. Average power and peak envelope power are NOT the same thing at all. They should remove the word "average" from the sentence...

Check your math guys.  Power averaged over one sinewave cycle IS rms-derived power.  So the word "average" in the ITU text is correct.

And the FCC limit on harmonic content just ensures you are dealing with a sinewave.

Average power, in general, is not PEP.  But PEP is average power over the single RF cycle at the peak of the envelope.
Logged
W5HRO
Member

Posts: 47




Ignore
« Reply #70 on: January 14, 2016, 05:14:43 PM »

Check your math guys.  Power averaged over one sinewave cycle IS rms-derived power.  So the word "average" in the ITU text is correct.

Your statment read "RF power is always expressed as RMS because the waveform is always sinusoidal."

Unfortunately you have no idea what you are talking about, not in regards to PEP.

Average power, in general, is not PEP.  But PEP is average power over the single RF cycle at the peak of the envelope.

Average power is not PEP in general, it's not average power period.

P.S. The main problem is that you have been confusing carrier power with modulated envelope power.
« Last Edit: January 14, 2016, 05:37:57 PM by W5HRO » Logged

W5HRO
Member

Posts: 47




Ignore
« Reply #71 on: January 14, 2016, 06:19:01 PM »

I did a quick search so to show you where your error is watch the Youtube video via the link below.

http://www.youtube.com/watch?v=pgzc4aU_HeY

Just after 7 minutes through the video around 7:23 he starts to draw the red average/mean (RF carrier) rectangle.
« Last Edit: January 14, 2016, 06:24:14 PM by W5HRO » Logged

WB4JTR
Member

Posts: 37




Ignore
« Reply #72 on: January 14, 2016, 07:17:11 PM »

Check your math guys.  Power averaged over one sinewave cycle IS rms-derived power.  So the word "average" in the ITU text is correct.

Your statment read "RF power is always expressed as RMS because the waveform is always sinusoidal."

Unfortunately you have no idea what you are talking about, not in regards to PEP.

Average power, in general, is not PEP.  But PEP is average power over the single RF cycle at the peak of the envelope.

Average power is not PEP in general, it's not average power period.

P.S. The main problem is that you have been confusing carrier power with modulated envelope power.

For PEP power, you can use the RMS calculation at the peak of the envelope because the waveform is ALWAYS just a sinewave.  (A sinewave contains no harmonics.)   That's why the ITU can use "average power over one cycle" to define PEP.  It's the same calculation the everyday rms/peak/average relations are based on for any sinewave.  And it's completely independent of envelope (modulation) shape.

Average power can not, in general, be PEP.  Average power in general depends on waveform shape.  But PEP is DEFINED as average power over a single cycle of a particular sinewave.  It is the LOCATION of this particular sinewave that is critical.  It must be located at the highest peak of the envelope.

We are discussing PEP of a SSB signal.  There is no carrier -- It is assumed to be completely suppressed.

PS:  I entered this thread to refute the assertion that the power in a single-tone SSB signal is 3dB below PEP.  To me, that's a crazy idea.  As far as the ITU's decision to base the definition of PEP on the average power in a particular sinewave, I completely understand their rationale.  How would you have defined it?

Logged
W5HRO
Member

Posts: 47




Ignore
« Reply #73 on: January 14, 2016, 07:39:19 PM »

because the waveform is ALWAYS just a sinewave.  (A sinewave contains no harmonics.)

No it is not and that's where you are wrong. You are right that a sinewave does not contain any 3rd order harmonics (be specific), but the PEP waveform is NOT always a sinewave.

I think most of us probably understand that you are referring to SSB and not AM and I'm only speaking for myself, but average power is mean power and is not PEP. Forget the fact that some people including myself tend to generalize avg/mean power as RMS power in discussions, but you have misinterpreted some basic facts.

Logged

WB4JTR
Member

Posts: 37




Ignore
« Reply #74 on: January 14, 2016, 09:48:51 PM »

because the waveform is ALWAYS just a sinewave.  (A sinewave contains no harmonics.)

No it is not and that's where you are wrong. You are right that a sinewave does not contain any 3rd order harmonics (be specific), but the PEP waveform is NOT always a sinewave.

I think most of us probably understand that you are referring to SSB and not AM and I'm only speaking for myself, but average power is mean power and is not PEP. Forget the fact that some people including myself tend to generalize avg/mean power as RMS power in discussions, but you have misinterpreted some basic facts.

A sinewave doesn't contain ANY harmonics.  Even harmonic distortion is also limited by the FCC.  If both odd and even orders weren't so limited, the single cycle on which PEP is based would be distorted, making the PEP calculation more difficult.

You keep repeating that average or mean power is not PEP.  That is true (as I have also repeated).  But PEP IS average (mean) power under the specific condition imposed by the ITU (and FCC).  By definition.  It is also RMS-derived power under the same condition.

I think the main problem here is failure to realize the time scale difference between the two concepts.  The average (mean) power used to define PEP is one RF cycle.  This is also the time scale used to establish the well-known peak/average/RMS sinewave relations.  The general audiophile concept of average power is based on a time scale of thousands of RF cycles.  And sometimes the RF waveform is ignored completely and averages are based on envelope or modulating audio alone.

In a way we're lucky PEP is based on the average (RMS) [ed-"RMS based"] power at the envelope peak.  Think what our 1500 watts would get us if it were based on the instantaneous peak power of that single cycle!
« Last Edit: January 20, 2016, 07:59:53 PM by WB4JTR » Logged
Pages: Prev 1 2 3 4 [5] 6 7 8 9 10 ... 22 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!