Do not be sorry for these "glitches" within your videos, i like them most, as they show that you are knowing your stuff! I like your calculator and the "reverse polish notation" as it do not need to put in any thoughts about typing failure! GREAT video, as alwas!! Keep on!
Thank you for your kind words. I have always leaned a little more towards liking RF but I do love to work with AF also. I moved to the HP RPN calculator in the 80's when they first came out (or I became aware of them) and totally agree with you that they are a superior style over the algebraic calculator. The HP 15C is probably one of the most famous and can still be bought new as HP still makes them. I am getting back into WiFi frequency range (2.4 GHz) as I have recently purchased equipment that will allow me to make measurements at those frequencies. One nice thing is the antennas are small.. :-) and easy to handle not like a 20 meter yagi up 50 feet in the air. Always good to hear from you, sir. Please keep in touch and publishing videos.
I´m too busy at the moment, as my job is absorbing nearly all my time currently...However i just finished my CombinedComperssorFilter unit and i´ll do a short video of it, as i´m really impressed about its performance. In addition i recently got a Telefunken M5 R2R-ProRecorder witch needs a lot of service, as well as some "big-ass" moving coil meters....may for some VU stuff... And the need of a new lab power supply, as mine is going wild at the moment... So a lot of work in line.... For me, all frequencies beyond 20kHz are RF ;) And please, do not call me sir, just say friend, buddy or alike, as i´m nearly half your age....;) I´d love to see more videos where you and Uncle Doug are doing things together, or just do a practicing video of what he shows us about phase splitter and such....it would be a great show, as you got all these fancy measuring stuff just sitting around and wait to be used to show the relationship between theorie and practical circuits. Just design a Common cathode circuit and add the bypass cap while hooked up to your spectrum analyzer that would be a real killer video! No one done it before, and you could be the first who snatch the mystery from this. I´ve done it some 10 years ago, but i was only for me and i done it in the lab of the company where i worked.... That was the time I discovered pretty much erverything about tube amps in gerneral and how the harmonic distorion spectrum is created. It´s about bias, voltage level, and current feedback path regardless of the type of tube beeing used, as long as you got the same topology (do not try to compare penthodes and triodes in terms of distortion as this is completely gernerated different). Uncle Doug is pulling at that blanket from time to time peeking under it, but he do not know the overall coherences, but he, in fact, is so close to open the grail to the creation of wanted distortion, he just needs some help, witch you can provide by the use of your measuring power. Stay basic with the circuit and do measurements then compare it to real life Amps, and you´ll see what i mean. Tweak the basic circuit and you´ll come very close to the one your refering to....trust me it´s in fact that damn simple, if and when you got the right measuring equipment.
I've always worked in audio, no need for me to be precise. Being aware of the differences between peak, average and RMS values is important to understand. I would add that one must understand that all three measures will remain relative to each other regardless of the measure method used. They all are indicative of the same output power just different measured units. I would think RMS was retooled in the 70's into a magic word, to make competitors average ratings look under powered to their magic RMS values. I think this video is the best you did of the three on this subject. You covered it very well here.! Thumbs up!
Thank you - I have to agree with you that this method of describing power was probably propagated by the audio industry. Who would ever want to have "average" power when you can have "RMS" power ? The problem is our feeling with the word “average” and there is also an “average” voltage that is a legitimate numerical value describing a relationship with the peak sinusoidal wave and it can be easy to mix the two up. On the other hand, I have a very nice technical document published by Dynaco around the early 70's where they very meticulously had to describe how they measured output power of their equipment to meet new imposed audio standards. I will find it and see if I can either post it or put a link to it assuming it is on the Internet. The audio industry saw that every manufacturer of audio equipment was exaggerating their numbers and the industry desperately needed a standard. I have also come to the conclusion that there is much worse things than calling something “RMS power”. While it may be a mathematical faux pas it has been doing a pretty good job for decades describing “real” power output.
ElPaso TubeAmps I would most certainly love to take a look at that Dynaco document. Sounds like an interesting read for sure. I'll keep my fingers crossed that you locate a copy online to share with us. Thanks again!
I´m not into RF very well, despite the fact that I studied EE with telecomunication toppic....we done some heavy RF stuff, but since i never was interested in that, i lost nearly all real RF knowledge.... Thanks for bringing this back...:)
actually when we discuss AC power, we have to consider average, real and appearant power. because real power is varied dependent on on the phase angle...
+Bob H Yes, but it seems we have used it so long that "RMS" power has become part of the technical lexicon and I think everyone knows what is intended by using the term. It has been used for a long time to express "constant" power but the technical and mathematically correct term is Average Power. RMS is used to express a useful value for positive and negative going signals like a sine wave as there is just as much power in the negative half cycle as there is in the positive half cycle but a simple average of a sine wave would be zero. That is why we first square all the terms to make them positive. Then we take the mean and then the square root and then multiplying the voltage and current, we end up with an "average" positive power level that is not going negative and positive like the sine wave. This average is not to be confused with the average value of a sine wave which is about 0.64 peak value (or to be exact, 2/Pi ) Hope this makes sense. Here is a video I made correcting some of my own mistakes using "RMS" power that you might like. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-_LzUnyfGAr8.html
The TV broadcast industry is transmitting complex waveforms with a very high peak to average power ratio. RMS power is the correct way to measure this. Read my response above.
I think it`s important to mention that the calculation done at 8:30 works only when voltage and current are in phase or more precisely proportional to each other. There are people measuring RMS voltage and RMS current without knowing if voltage and current are proportional to each other. If we have a 90 degree displacement to each other the AVG power is equal zero but simply multiply the two values will give you an amount of active power which actually don`t exist.
IvanIvan1974 Exactly my point, when they are not in phase (o deg) we have power that isnt actually doing anything...hence we have apoearant power derived from E * I , then we have real power derived ftom E*I / PF
Some of the inexpensive AD8703-based power meters seen on E-Bay (e.g. 1-MHZ-to-500-MHZ-RF-power-meter-logarithmic-detection-power-detection) are average responding. Others are RMS responding (e.g. 50HZ-3.8GHZ RF Radio Frequency Detector / Power Detection / RMS detector AD8362). There is a difference.
Mathematically, that of a sine wave, peak power is exactly two times average power (average power often incorrectly referred as RMS power). Unfortunately for the Bird 43 without the addition of the PEP board, the response of the meter is terribly slow when trying to measure peak power. So, like you say, it is just a guesstemate of how much PEP power is actually going thru the meter. I think a reasonable guess would be the PEP power is about four times what the needle is kicking up to on the Bird. Just my thoughts.
Yep, it is just something i noticed along the way trying to figure out to get the best accuracy in reading power using a peak detector-dmm, a scope, (old)spectrum analyzer bird or fft on a brand new r&s scope. Best result (for me) compared with a very expensive and accurate and calibrated r&s com analyzer set is a dBm level measurement with the fft of my r&s scope on a self build and very flat dummy load. You make nice and interesting vids 👍🏻
There is no misuse of the term "RMS Power". Both Average power and RMS power are real engineering terms for AC power engineers, audio engineers, RF engineers etc.. The difference is in the *method* you use to arrive at the *average*. They are not the same. Average power is simply the average (or mean) of samples taken at regular intervals. As you point out in your video, average power is the integral, or the area under the curve. For a perfect sine wave, the area under the curve is the square root of 2 / 2 (or .707) times the peak power. But this does not apply to more complex waveforms like a square wave for example. But what if you wanted a DC equivalent for a waveform that is more complex than a simple sine wave? What if it had high peaks? Do you let those peaks inflate your average? What can you do? RMS is a method of taking an average so that short peaks in current and voltage do not inflate your average. It's also known as the quadratic mean. It's the square root of the average of the square of each of the samples (voltage or current). RMS power (or average power) is the product of RMS voltage and the RMS current. Prms = Irms * Erms The problem is that amateur radio and consumer watt meters only respond to the average power. But measuring the true power levels of complex waveforms can be very difficult. RMS power and Average power are not the same. The "Form factor" of an alternating current waveform (signal) is the ratio of the RMS (root mean square) value to the average value. There are commercial-grade power meters that will measure average and peak power. Recently, it's been possible to actually measure RMS power and it's done regularly in the cellular and the military RF industry. RMS power detectors are the best for this application as they measure the true RMS power level of the signal. Take a close look at this Analog Device power detector chip. It actually takes voltage and current measurements, squares them and then averages them. It does accurate rms-to-dc conversion from 50 MHz to 9 GHz. www.analog.com/en/products/rf-microwave/rf-power-detectors/rms-responding-detector/adl5902.html For all practical sense when measuring a *Continuous Wave (CW) carrier* as you are doing, RMS and Average power *is the same*. cp.literature.agilent.com/litweb/pdf/5965-6630E.pdf sine.ni.com/nips/cds/view/p/lang/en/nid/208934 www.analog.com/media/en/training-seminars/tutorials/MT-082.pdf www.quora.com/What-is-RMS-power Konrad Roeder, WA4OSH
Oh and by the way... Your oscilloscope reads only volts. No current measurement is taken. The method assumes a perfect 50 ohm load, which I will *guarantee* that it's not. Once you operate into a non-50 ohm load, all bets are off.
Oh and Bird Watt meters use a directional coupler and are reading *average* power, not RMS power. There is a difference. If you had a 30 or 40 dB power attenuator, then you could use a commercial Power Meter to measure Average, Peak and RMS power.
