RE: [AMRadio] Re: MODULATION POWER REQUIRED
> The waveform of the rf signal is not the same thing as the waveform of the > envelope pattern of a modulated waveform. We could term this "modulation power of the transmitter" to distinguish it from PEP. >When we talk about the average > power output, or mean power output of a transmitter, we are talking about > the average that is integrated over several cycles of the waveform of the > audio that modulates the carrier. With PEP, you are selecting the one > highest peak, which may occur infrequently, or possibly only once during > the > entire transmission, and basing your power output reading on the average > rf > power during that peak. This has very little to do with the apparent > loudness of the signal, or the amount of interference it may generate. 73 Gary K4FMX __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] Re: MODULATION POWER REQUIRED
From: "Gary Schafer" <[EMAIL PROTECTED]> Subject: RE: [AMRadio] Re: MODULATION POWER REQUIRED The average VOLTAGE of a sine wave is meaningless. You don't use it to calculate average power. We are looking for the RMS value. When we are talking about PEP and the "average power over one or more cycles" we are talking about the RF cycles of the transmitter. Each part of the audio envelope, even the narrowest peaks, are going to be composed of (contain) many RF cycles in each of those peaks. Being that all of those RF cycles are pure sine waves the rules of .707 times the peak voltage to find RMS voltage will always apply. The amplitude of those RF cycles will vary with the modulation envelope level. To measure PEP we pick a point that is the highest part of the modulation envelope (peak) and there will be many many pure RF sine waves contained there. We want to find the average power in those sine waves at that particular time. The average voltage of a sinewave is zero, since there is precisely as much of the waveform above the baseline as below. That is why the DC plate meter on a properly operating, 100% modulated modulated AM transmitter doesn't move with modulation, and that's also why a transformer will not pass DC. The RF signal is always composed of sine waves no matter if there is modulation or no modulation. It also doesn't matter what the wave shape of the modulating signal is either, tones, voice or whatever, the RF coming out of the transmitter is still going to be sine waves. If it were not there would be serious harmonics generated. The waveform of the rf signal is not the same thing as the waveform of the envelope pattern of a modulated waveform. When we talk about the average power output, or mean power output of a transmitter, we are talking about the average that is integrated over several cycles of the waveform of the audio that modulates the carrier. With PEP, you are selecting the one highest peak, which may occur infrequently, or possibly only once during the entire transmission, and basing your power output reading on the average rf power during that peak. This has very little to do with the apparent loudness of the signal, or the amount of interference it may generate. PEP is most useful for measuring the output capability, AKA "headroom", of an amplifier, to determine the maximum output level before the amplifier goes into saturation and flat-tops. The average-reading RF output meter works much like an audio VU meter. The mechanical mass of the analogue meter movement integrates or "averages out" the rf power to the equivalent amount of DC power that would heat a resistive load to the same temperature during the measurement interval. There is no such thing a an "rf power" meter, at least when we are talking about an instrument that most amateurs could afford. The so-called "wattmeters" are really rf voltmeters calibrated to the read the level of power delivered when the measured voltage is imposed across a known resistance. Most rf wattmeters are calibrated to work into a 50 or 72-ohm load. At any other load impedance, the reading is erroneous. An alternative to the rf voltmeter is an rf ammeter. Those have been in use since the 20's. They are not usually calibrated in watts, but in rf amperes, so you have to use Ohm's law to calculate output power. In either case, the impedance of the load must be precisely known in order to get an accurate reading, and the load must be purely resistive, not reactive. Very few amateur radio antennas present a perfectly resistive 50-ohm load, as reflected back through the feedline, to the transmitter. Average power output measurements work with SSB, if the ballistic characteristics of the meter movement are known, in the same manner as the VU meter. With the VU meter, a standard ballistic characteristic was defined, and the manufacturers built analogue meters to those standards. In the same manner, the DC input measurement works with SSB, as long as the ballistic characteristics of the plate current meter are known. The vast majority of D'arsonval meter movements are perfectly satisfactory for this measurement. With the l.e.d. meters that are ever more replacing the electro-mechanical analogue meter, it is easier to measure p.e.p. than it is average power. The latter measurement would require some kind of integrating circuitry to meaningfully measure average, or mean voltage or current and thus power. Don k4kyv __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.
RE: [AMRadio] Re: MODULATION POWER REQUIRED
The average VOLTAGE of a sine wave is meaningless. You don't use it to calculate average power. We are looking for the RMS value. The RF signal is always composed of sine waves no matter if there is modulation or no modulation. It also doesn't matter what the wave shape of the modulating signal is either, tones, voice or whatever, the RF coming out of the transmitter is still going to be sine waves. If it were not there would be serious harmonics generated. When we are talking about PEP and the "average power over one or more cycles" we are talking about the RF cycles of the transmitter. Each part of the audio envelope, even the narrowest peaks, are going to be composed of (contain) many RF cycles in each of those peaks. Being that all of those RF cycles are pure sine waves the rules of .707 times the peak voltage to find RMS voltage will always apply. The amplitude of those RF cycles will vary with the modulation envelope level. To measure PEP we pick a point that is the highest part of the modulation envelope (peak) and there will be many many pure RF sine waves contained there. We want to find the average power in those sine waves at that particular time. If you have a fast enough scope you can see exactly what is happening. Look at a transmitter modulated with a tone and you will see the familiar modulation envelope. Spread that way out by increasing the sweep speed and turn up the brightness and you will see all the RF cycles under the modulation envelope. Those are all pure sine waves and will always be. A 3.8 MHz signal with 1000 cycle modulation on it will show a 1000 cycle modulation envelope and contained in that envelope there will be 3800 RF cycles. You can break that down further and say that half of that audio envelope will be positive and half negative. So then the positive half will have 1900 RF cycles. We could break that down further and find how many cycles are near the peak if we wish. But the point is they are all RF cycles and good sine waves on which power is measured. If you are modulating the transmitter with speech the RF power still comes out in perfect sine waves regardless of the modulating waveform. If you were trying to measure audio power at the audio frequencies in this manner then it would not be pure sine waves with speech. 73 Gary K4FMX > -Original Message- > From: [EMAIL PROTECTED] [mailto:amradio- > [EMAIL PROTECTED] On Behalf Of Jim Candela > Sent: Friday, February 15, 2008 9:54 AM > To: amradio@mailman.qth.net > Subject: [AMRadio] Re: MODULATION POWER REQUIRED > > > > Don, > >It seems that we have defined PEP power pretty well: > > >"Well, PEP is defined as the AVERAGE power over at least one RF cycle at > > the most powerful point of the envelope." > Now, since we do not speak with sine waves, the average "power point of > the envelope" is going to be less than 0.636 (sine wave average) of the > peak value. With many voices the average might be 0.2 to 0.5 of the peak. > Doesn't this mean we can increase the peak power until the PEP as we have > defined it hits 1500 watts? It seems that many of us confuse peak power > with Peak Envelope Power. The definitions are different. If I have this > correct, then unprocessed voice peaks can be increased until the PEP legal > limit is achieved, and the carrier level might be a lot more than 375 > watts. Maybe the KW1, or Johnson Desk KW at Hi-Tap are still legal? > > Regards, > Jim > __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] RE: MODULATION POWER REQUIRED
AMEN!!! Rev. Don W4BWS - Original Message - From: "D. Chester" <[EMAIL PROTECTED]> To: Sent: Friday, February 15, 2008 3:46 AM Subject: [AMRadio] RE: MODULATION POWER REQUIRED Most of us stay somewhere within the ballpark of the so-called "legal limit", and worrying about an occasional voice peak that might jump a little over, every now and again for a milliseconds or two during the course of an entire old-buzzard transmission, is MUCH ADO ABOUT NOTHING. Is everyone that picky and consientious in regard to exceeding the posted speed limit when we drive, something that can actually put our own or someone else's life in danger? We need to be more concerned about overmodulation, flat-topping and other improper conditions that generate spurious distortion products and do actual harm on the bands by causing unnecessary splatter and interference beyond the limits of our normal channel width. (Not the same thing as the higher frequency audio components that occur naturally in our voice signals.) Don k4kyv __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: Speech Processing Re: [AMRadio] RE: MODULATION POWER REQUIRED
I have not looked at the EICO modulator clipper. But I would expect it to be the type of speech processor shown in the ARRL handbooks from the 50's and 60's. I work with both tubes and solid state. Today this is the kind of thing that would be done with DSP. Why? Remote control! Look through some of the older ARRL Handbooks. These are easy to do in either tube or transistor circuits. In tube circuits it was common to use inductor/capacitor low pass filters. In transistor designs it was common to use active filters. Bob Macklin K5MYJ Seattle, Wa, "Real Radios Glow in the Dark" - Original Message - From: "RJ Mattson" <[EMAIL PROTECTED]> To: "Discussion of AM Radio in the Amateur Service" Sent: Friday, February 15, 2008 7:25 AM Subject: Speech Processing Re: [AMRadio] RE: MODULATION POWER REQUIRED > Bob > Let me know what u decide on. I'm running qrp AM and need every ounce to be > intelligence. > I can't waste power to be hifi. > Was your ckt similar to the Eico modulator clipper? > I assume you will strictly use tooobes? :-) > > bob...w2ami x wn2ami 1962 > > > - Original Message - > From: "Bob Macklin" <[EMAIL PROTECTED]> > Subject: Re: [AMRadio] RE: MODULATION POWER REQUIRED > > > I understand the modern RICEBOXES had speech processing the clips peaks and > filters the audio. > > I had a tube speech processor back in the 60's. It was a classic > clipper/filter. It worked very well. For a lower power transmitter like the > smaller Heath DX units you can increase the voice level clipping and > filtering there by generating a higher modulation index without over > modulating. And if properly set you won't exceed the legal limits. > > I am going to build another one for my current DX-60. > > Bob Macklin > K5MYJ > > __ > Our Main Website: http://www.amfone.net > AMRadio mailing list > Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ > List Rules (must read!): http://w5ami.net/amradiofaq.html > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > To unsubscribe, send an email to [EMAIL PROTECTED] with > the word unsubscribe in the message body. > __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Speech Processing Re: [AMRadio] RE: MODULATION POWER REQUIRED
Bob Let me know what u decide on. I'm running qrp AM and need every ounce to be intelligence. I can't waste power to be hifi. Was your ckt similar to the Eico modulator clipper? I assume you will strictly use tooobes? :-) bob...w2ami x wn2ami 1962 - Original Message - From: "Bob Macklin" <[EMAIL PROTECTED]> Subject: Re: [AMRadio] RE: MODULATION POWER REQUIRED I understand the modern RICEBOXES had speech processing the clips peaks and filters the audio. I had a tube speech processor back in the 60's. It was a classic clipper/filter. It worked very well. For a lower power transmitter like the smaller Heath DX units you can increase the voice level clipping and filtering there by generating a higher modulation index without over modulating. And if properly set you won't exceed the legal limits. I am going to build another one for my current DX-60. Bob Macklin K5MYJ __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] Re: MODULATION POWER REQUIRED
Don, It seems that we have defined PEP power pretty well: >"Well, PEP is defined as the AVERAGE power over at least one RF cycle at > the most powerful point of the envelope." Now, since we do not speak with sine waves, the average "power point of the envelope" is going to be less than 0.636 (sine wave average) of the peak value. With many voices the average might be 0.2 to 0.5 of the peak. Doesn't this mean we can increase the peak power until the PEP as we have defined it hits 1500 watts? It seems that many of us confuse peak power with Peak Envelope Power. The definitions are different. If I have this correct, then unprocessed voice peaks can be increased until the PEP legal limit is achieved, and the carrier level might be a lot more than 375 watts. Maybe the KW1, or Johnson Desk KW at Hi-Tap are still legal? Regards, Jim __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] RE: MODULATION POWER REQUIRED
I understand the modern RICEBOXES had speech processing the clips peaks and filters the audio. I had a tube speech processor back in the 60's. It was a classic clipper/filter. It worked very well. For a lower power transmitter like the smaller Heath DX units you can increase the voice level clipping and filtering there by generating a higher modulation index without over modulating. And if properly set you won't exceed the legal limits. I am going to build another one for my current DX-60. Bob Macklin K5MYJ Seattle, Wa, "Real Radios Glow in the Dark" - Original Message - From: "D. Chester" <[EMAIL PROTECTED]> To: Sent: Friday, February 15, 2008 1:46 AM Subject: [AMRadio] RE: MODULATION POWER REQUIRED > Most of us stay somewhere within the ballpark of the so-called "legal > limit", and worrying about an occasional voice peak that might jump a little > over, every now and again for a milliseconds or two during the course of an > entire old-buzzard transmission, is MUCH ADO ABOUT NOTHING. Is everyone > that picky and consientious in regard to exceeding the posted speed limit > when we drive, something that can actually put our own or someone else's > life in danger? > > We need to be more concerned about overmodulation, flat-topping and other > improper conditions that generate spurious distortion products and do actual > harm on the bands by causing unnecessary splatter and interference beyond > the limits of our normal channel width. (Not the same thing as the higher > frequency audio components that occur naturally in our voice signals.) > > Don k4kyv > > __ > Our Main Website: http://www.amfone.net > AMRadio mailing list > Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ > List Rules (must read!): http://w5ami.net/amradiofaq.html > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > To unsubscribe, send an email to [EMAIL PROTECTED] with > the word unsubscribe in the message body. > __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] RE: MODULATION POWER REQUIRED
Most of us stay somewhere within the ballpark of the so-called "legal limit", and worrying about an occasional voice peak that might jump a little over, every now and again for a milliseconds or two during the course of an entire old-buzzard transmission, is MUCH ADO ABOUT NOTHING. Is everyone that picky and consientious in regard to exceeding the posted speed limit when we drive, something that can actually put our own or someone else's life in danger? We need to be more concerned about overmodulation, flat-topping and other improper conditions that generate spurious distortion products and do actual harm on the bands by causing unnecessary splatter and interference beyond the limits of our normal channel width. (Not the same thing as the higher frequency audio components that occur naturally in our voice signals.) Don k4kyv __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] RE: MODULATION POWER REQUIRED
When you run over 25% carrier power but only modulate to the 1500W PEP limit you do not produce as much audio power at the receiving end as you if you run the 375W of carrier and modulate it to the 1500W PEP Limit. Bob Macklin K5MYJ Seattle, Wa, "Real Radios Glow in the Dark" - Original Message - From: "Jim Candela" <[EMAIL PROTECTED]> To: Sent: Thursday, February 14, 2008 7:01 PM Subject: [AMRadio] RE: MODULATION POWER REQUIRED > > Reply by Jim, WD5JKO: > > John, and Group, > > Your PEP definition agrees with references from other sources. My math > is a little weak, but doesn't this suggest that the 375 watt carrier > limit we arbitrarily impose on ourselves is a low ball value, and with > the definition below can't we run more carrier at 100% modulation and > still meet the 1500 watt PEP output limitation? I seem to recall that > Don, K4KYV had some pretty persuasive arguments countering the > presumption we adopted years ago. This was back when the 1000W DC input > "Grandfather Rule" was expiring for AM. > > > http://www.its.bldrdoc.gov/fs-1037/dir-027/_3903.htm > > peak envelope power (of a radio transmitter) [PEP, pX, PX]: 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. [NTIA] [RR] (188) > > > http://www.vk1od.net/VSWR/W4.htm > Peak Envelope Power 'pX' (s1.157) means the average power supplied to > the antenna transmission line by a transmitter during one radiofrequency > cycle at the crest of the modulation envelope taken under normal > operating conditions. > > John, WA5BXO said: > For PEP it should read: > "Well, PEP is defined as the AVERAGE power over at least one RF cycle at > the most powerful point of the envelope." > > 73, > Jim > WD5JKO > > __ > Our Main Website: http://www.amfone.net > AMRadio mailing list > Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ > List Rules (must read!): http://w5ami.net/amradiofaq.html > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > To unsubscribe, send an email to [EMAIL PROTECTED] with > the word unsubscribe in the message body. > __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] RE: MODULATION POWER REQUIRED
Reply by Jim, WD5JKO: John, and Group, Your PEP definition agrees with references from other sources. My math is a little weak, but doesn't this suggest that the 375 watt carrier limit we arbitrarily impose on ourselves is a low ball value, and with the definition below can't we run more carrier at 100% modulation and still meet the 1500 watt PEP output limitation? I seem to recall that Don, K4KYV had some pretty persuasive arguments countering the presumption we adopted years ago. This was back when the 1000W DC input "Grandfather Rule" was expiring for AM. http://www.its.bldrdoc.gov/fs-1037/dir-027/_3903.htm peak envelope power (of a radio transmitter) [PEP, pX, PX]: 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. [NTIA] [RR] (188) http://www.vk1od.net/VSWR/W4.htm Peak Envelope Power 'pX' (s1.157) means the average power supplied to the antenna transmission line by a transmitter during one radiofrequency cycle at the crest of the modulation envelope taken under normal operating conditions. John, WA5BXO said: For PEP it should read: "Well, PEP is defined as the AVERAGE power over at least one RF cycle at the most powerful point of the envelope." 73, Jim WD5JKO __ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/amradio@mailman.qth.net/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
