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From: (Dave=A0Hall)
On 6 Oct 2004 14:37:46 -0700, (Jim Hampton) wrote: Hello, Twist Dave was referring to 'S' units at the other end of the circuit. One 'S' unit is *supposidly* equal to 6 dB. 6 dB is an increase in power of four times. (You know that, I know that,) Jim has yet to answer, but here you are answering for him, Davie. What confidence you display. Again, for the record, Jim, are you in agreement that a "peak and tune" will increase S units on a 4 watt stock radio? most knowledgable people know that, Agreed, as you are the ONLY one arguing that you can change the net increase on a stck 4 watt radio in regards to S units. That alone should tell you what you lack and need to know, but your comprehension skills have been abused. and I suspect Twisty knows that as well. He just likes to argue for the sake of arguing. I exchanged ideas on this subject and in this thread with sideband and now Jim, and as usual, you are alone in your claims. *Only* you are referring to your exchanges as arguing, no one else. Get over yourself and educate yourself on how to conduct proper communication and public debate without allowing your temper to exhibit control. In other words, stop taking everyhting so personal. It's not my fault your ego makes you feel this way when you attempt to debate issues, but I don't mind being your sounding board for blame. It's true that most CB "S" meters are far from linear, and consistent. On the lower part of the scale, 1 "S" unit might be only 2 or 3 db. At the upper end, 1 "S" unit might be closer to 10db. But the theory is sound. Dave "Sandbagger" And has nothing to do with your ignorant and wrong claim that a peak and tune increases the S units on a 4 watt stock radio. |
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On Thu, 7 Oct 2004 10:05:13 -0400, (Twistedhed)
wrote: From: (Jim*Hampton) Hello, Twist Yo' Jim. Dave was referring to 'S' units at the other end of the circuit. When I took exception to his words, he was speaking of S units received by another radio, arrived via the peaking of the 4 watt radio that was of topic.. No, that's WRONG. Another shining example of your inability to comprehend. I stated that peaking a 4 watt radio will improve that radio's signal to another's receive station. But that improvement will be very minimal, as it takes 6db (4x increase) more in power to gain 1 "S" unit on the received end. Dave "Sandbagger" |
On Thu, 07 Oct 2004 07:06:26 -0400, Dave Hall
wrote in : On Wed, 06 Oct 2004 11:47:29 -0700, Frank Gilliland wrote: snip Compression -- a term usually applied to audio conditioning where the amplification of a signal is varied inversely to it's input level. One of the most common types of audio compressor is called "constant volume amplifier". That is but one type of compression. For a more detailed discussion of RF amplifier compression, please refer to the following related link: http://cp.literature.agilent.com/lit...5965-7710E.pdf Generally speaking, amplifier compression occurs when the input:output power ratio no longer increases db for db. You should know me by now -- I just -have- to disagree. The use of the term 'compression region' is really a misnomer. It's properly described as a nonlinear region. The reason is that different devices behave differently, and while a few devices (some transistors, a few tubes, incandescent lightbulbs) have nonlinear characteristics similar to compression, the fact is that nothing is being 'compressed', and the vast majority of other devices have nonlinear regions that do not resemble compression. And whether that nonlinear region is gradual or sharp, it's still clipping because it's a limitation of the device. It also causes distortion that is characteristic of clipping. And yes, saturation is within the nonlinear region. I'll give him this one. This may be a matter of semantics, like noting the difference between 'weight' and 'mass'. I had these things drilled into my brain by my profs for the simple reason that using the wrong term can cause a misunderstanding. And that's what I believe is happening when people substitute the term 'compression' for when the transistor has exceeded the limits of linearity and subsequently clips, be it hard or soft. But no matter what you call it, the result is distortion. But the problem here is that the term 'compression' has been adopted by voodoo techs as a euphamism for 'clipping', making it sound as if the distortion-causing effect is not only benign, but sometimes preferred. It is neither. After reading the link, you might want to revise your definition. There are a bunch of very talented engineers here who would be a bit insulted to find out that you refer to them as "voodoo techs". I'll stick with my definition. And while I may take issue with some of the more liberal definitions used by engineers these days, I should point out that I worked for HP (Agilent) several years ago and I'm not a big fan of their engineering department. But you are right about one thing. a -33dbc harmonic rating from a single carrier signal is pretty poor. Perhaps a chebychev lowpass filter on the output will fix it up..... That would be nothing more than a kludge. The fault is in the design. The response isn't even close to linear. That may be due to the bias class, the bias regulator, the choice of active device, or just crappy engineering overall. I suspect it's a little of everything. Usually, if it is a push-pull design, device matching plays an important part. Bias is also important, as is impedance matching. But even a "good" design should have a follow-up low pass filter to minimize any harmonic content. Absolutely. But even filters have limitations. Assuming Brian's amp has 350 watt noise figures in the neighborhood of -18 to -24 dB (not unrealistic), it would take a mighty stout filter to clean it up! |
On Thu, 07 Oct 2004 13:58:13 -0700, Frank Gilliland
wrote: On Thu, 07 Oct 2004 07:06:26 -0400, Dave Hall wrote in : On Wed, 06 Oct 2004 11:47:29 -0700, Frank Gilliland wrote: snip Compression -- a term usually applied to audio conditioning where the amplification of a signal is varied inversely to it's input level. One of the most common types of audio compressor is called "constant volume amplifier". That is but one type of compression. For a more detailed discussion of RF amplifier compression, please refer to the following related link: http://cp.literature.agilent.com/lit...5965-7710E.pdf Generally speaking, amplifier compression occurs when the input:output power ratio no longer increases db for db. You should know me by now -- I just -have- to disagree. That's what makes discussion interesting. Unless, of course the other party is nameless sociopath..... ;-) The use of the term 'compression region' is really a misnomer. It's properly described as a nonlinear region. A device can be non-linear without going into compression. The way I learned it, compression is a specific term that applies when a normally linear device loses linearity as it approaches it's maximum drive level. The reason is that different devices behave differently, and while a few devices (some transistors, a few tubes, incandescent lightbulbs) have nonlinear characteristics similar to compression, the fact is that nothing is being 'compressed', and the vast majority of other devices have nonlinear regions that do not resemble compression. Exactly! That's why compression refers to a specific condition, so as to differentiate it from other forms of non-linerarity. Certain class "C" "Modulator" type amplifiers, for example, deliberately run in the non-linear region just above device cutoff, to take advantage of the "swing" effect of the device. It's non-linear, but it's not compressed. And whether that nonlinear region is gradual or sharp, it's still clipping because it's a limitation of the device. It also causes distortion that is characteristic of clipping. And yes, saturation is within the nonlinear region. I differentiate the term "clipping" from "compression" by the application in which the terms are used. In an application such as a broadband amplifier with a broad spectrum of carriers (Such as a CATV amp), is applied to the input, the term compression applies as you reach the point of non-linear gain and the incidents of composite second order beats rises disproportionately. I look at "clipping" as a momentary chopping off of an otherwise linear signal reproduction, such as what you would encounter with AM modulation peaks which run out of headroom in an amplifier, which would otherwise be still in the linear range when unmodulated. You can still "clip" while not being fully into compression. Maybe I'm over-analyzing these terms, but that's me..... I'll give him this one. This may be a matter of semantics, like noting the difference between 'weight' and 'mass'. I had these things drilled into my brain by my profs for the simple reason that using the wrong term can cause a misunderstanding. And that's what I believe is happening when people substitute the term 'compression' for when the transistor has exceeded the limits of linearity and subsequently clips, be it hard or soft. But no matter what you call it, the result is distortion. No argument there. But the problem here is that the term 'compression' has been adopted by voodoo techs as a euphamism for 'clipping', making it sound as if the distortion-causing effect is not only benign, but sometimes preferred. It is neither. After reading the link, you might want to revise your definition. There are a bunch of very talented engineers here who would be a bit insulted to find out that you refer to them as "voodoo techs". I'll stick with my definition. And while I may take issue with some of the more liberal definitions used by engineers these days, I should point out that I worked for HP (Agilent) several years ago and I'm not a big fan of their engineering department. While the link I provided, was put out by Agilent, it was one of many examples. I don't work for them either, but I do work with some talented RF engineers, and we use the term compression frequently to describe the point where linear gain ceases, and distortion products increase disproportionately. But you are right about one thing. a -33dbc harmonic rating from a single carrier signal is pretty poor. Perhaps a chebychev lowpass filter on the output will fix it up..... That would be nothing more than a kludge. The fault is in the design. The response isn't even close to linear. That may be due to the bias class, the bias regulator, the choice of active device, or just crappy engineering overall. I suspect it's a little of everything. Usually, if it is a push-pull design, device matching plays an important part. Bias is also important, as is impedance matching. But even a "good" design should have a follow-up low pass filter to minimize any harmonic content. Absolutely. But even filters have limitations. Assuming Brian's amp has 350 watt noise figures in the neighborhood of -18 to -24 dB (not unrealistic), it would take a mighty stout filter to clean it up! A 5 pole filter should bring it into line. All he would need is an additional 30db of attenuation Dave "Sandbagger" http://home.ptd.net/~n3cvj |
On Fri, 08 Oct 2004 07:08:10 -0400, Dave Hall
wrote in : On Thu, 07 Oct 2004 13:58:13 -0700, Frank Gilliland wrote: On Thu, 07 Oct 2004 07:06:26 -0400, Dave Hall wrote in : On Wed, 06 Oct 2004 11:47:29 -0700, Frank Gilliland wrote: snip Compression -- a term usually applied to audio conditioning where the amplification of a signal is varied inversely to it's input level. One of the most common types of audio compressor is called "constant volume amplifier". That is but one type of compression. For a more detailed discussion of RF amplifier compression, please refer to the following related link: http://cp.literature.agilent.com/lit...5965-7710E.pdf Generally speaking, amplifier compression occurs when the input:output power ratio no longer increases db for db. You should know me by now -- I just -have- to disagree. That's what makes discussion interesting. Unless, of course the other party is nameless sociopath..... ;-) Which one? There are so many..... The use of the term 'compression region' is really a misnomer. It's properly described as a nonlinear region. A device can be non-linear without going into compression. The way I learned it, compression is a specific term that applies when a normally linear device loses linearity as it approaches it's maximum drive level. The problem is the application; i.e, the operational limits of the device. More below. The reason is that different devices behave differently, and while a few devices (some transistors, a few tubes, incandescent lightbulbs) have nonlinear characteristics similar to compression, the fact is that nothing is being 'compressed', and the vast majority of other devices have nonlinear regions that do not resemble compression. Exactly! That's why compression refers to a specific condition, so as to differentiate it from other forms of non-linerarity. Certain class "C" "Modulator" type amplifiers, for example, deliberately run in the non-linear region just above device cutoff, to take advantage of the "swing" effect of the device. ......huh? That statement looks like a train-wreck. Assuming we're talking Class C for both types, a device is usually pushed towards -saturation-, and the result is clipping which forms a psuedo-square wave that packs more energy than a sine wave, and making the stage more efficient (a design that evolved into the Class E amplifier). Also, Class C devices are -biased- above cutoff by definition. But what is this "swing effect" you describe? I have never heard of a -device- having such an effect unless it was a self-resonant device. Last time I checked, most transistors don't tend to be self-resonant below 30 MHz..... It's non-linear, but it's not compressed. That's the point. It's -not- compressed. I see no reason to place that label on a portion of a curve only because it loosly resembles one of the characteristics of compression yet doesn't fall within its definition. To me it's like using the word 'pill' to describe an RF transistor, or 'swing' to describe modulation. And whether that nonlinear region is gradual or sharp, it's still clipping because it's a limitation of the device. It also causes distortion that is characteristic of clipping. And yes, saturation is within the nonlinear region. I differentiate the term "clipping" from "compression" by the application in which the terms are used. In an application such as a broadband amplifier with a broad spectrum of carriers (Such as a CATV amp), is applied to the input, the term compression applies as you reach the point of non-linear gain and the incidents of composite second order beats rises disproportionately. I look at "clipping" as a momentary chopping off of an otherwise linear signal reproduction, such as what you would encounter with AM modulation peaks which run out of headroom in an amplifier, which would otherwise be still in the linear range when unmodulated. You can still "clip" while not being fully into compression. Maybe I'm over-analyzing these terms, but that's me..... I see the image in your brain -- "clipping" suggests a straight-line cut from the top of the wave. And I understand your definition of 'compression' as the transitional zone between linearity and clipping. But clipping, by definition, is caused when the signal exceeds the limits of the device. And that's exactly what happens when the output is pushed into the nonlinear region because it's operation is intended to be limited to the linear region (otherwise it's not a linear amp). I'll give him this one. This may be a matter of semantics, like noting the difference between 'weight' and 'mass'. I had these things drilled into my brain by my profs for the simple reason that using the wrong term can cause a misunderstanding. And that's what I believe is happening when people substitute the term 'compression' for when the transistor has exceeded the limits of linearity and subsequently clips, be it hard or soft. But no matter what you call it, the result is distortion. No argument there. But the problem here is that the term 'compression' has been adopted by voodoo techs as a euphamism for 'clipping', making it sound as if the distortion-causing effect is not only benign, but sometimes preferred. It is neither. After reading the link, you might want to revise your definition. There are a bunch of very talented engineers here who would be a bit insulted to find out that you refer to them as "voodoo techs". I'll stick with my definition. And while I may take issue with some of the more liberal definitions used by engineers these days, I should point out that I worked for HP (Agilent) several years ago and I'm not a big fan of their engineering department. While the link I provided, was put out by Agilent, it was one of many examples. I don't work for them either, but I do work with some talented RF engineers, and we use the term compression frequently to describe the point where linear gain ceases, and distortion products increase disproportionately. I've known many talented engineers who learned switch terminology backwards: for example, they would describe a 6-position rotory switch as a 6-pole single-throw. I've known some talented engineers who didn't know the difference between 'active' and 'passive'. I've even known a couple talented engineers who thought electrons flowed from positive to negative. I guess I'm just anal (like THAT'S a suprise!). But you are right about one thing. a -33dbc harmonic rating from a single carrier signal is pretty poor. Perhaps a chebychev lowpass filter on the output will fix it up..... That would be nothing more than a kludge. The fault is in the design. The response isn't even close to linear. That may be due to the bias class, the bias regulator, the choice of active device, or just crappy engineering overall. I suspect it's a little of everything. Usually, if it is a push-pull design, device matching plays an important part. Bias is also important, as is impedance matching. But even a "good" design should have a follow-up low pass filter to minimize any harmonic content. Absolutely. But even filters have limitations. Assuming Brian's amp has 350 watt noise figures in the neighborhood of -18 to -24 dB (not unrealistic), it would take a mighty stout filter to clean it up! A 5 pole filter should bring it into line. All he would need is an additional 30db of attenuation Don't forget that as you increase the power you need to increase the attenuation. This is because of the changes in the equipment rules regarding harmonic emissions. The limit is now absolute whereas before it was relative to signal strength. Regardless, a LP filter won't filter the splatter. |
From: (Dave=A0Hall)
On Thu, 7 Oct 2004 10:52:18 -0400, (Twistedhed) wrote: And has nothing to do with your ignorant and wrong claim that a peak and tune increases the S units on a 4 watt stock radio. You are a basket case. And your insultive demeanor and erratic behavior is beyond your self-control whenever you are reminded we are speaking of a topic that was being discussed, not a hypothetical radio invoked by yourself to change the topic. Your ability to comprehend even the simplest concepts is severely impeded. Complaining about me and blaming me for your radio incompetence isn't going to change your inability to remain on topic or take away your ignorance concerning S units. This is seconded only by your penchant to spin and twist words in order to avoid admitting that you misunderstood the concept. A concept only you appear to be familiar with. I'll let Jim or anyone else set you straight. Jim isn't bailing you out, In fact, no one has agreed with you, so stop looking to others for help. But suffice to say, you're in over your head. Dave "Sandbagger" I'm not the one that claimed S units can be increased on a 4 watt radio with a peak and tune,,,you did. Learn to accept your failures and those things you are unable to change without the need to blame others. |
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