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#11
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I have used the BIG caps as used on the audio amps on my RF power amp and
it did help on the current spikes that was needed on SSB peaks. Without the Cap, the voltage could drop to 10.5 volts on current peaks measured at the amp, now it might go to 12 - 12.5 volts only rising to the supplied 13.8 volts in the system. It help to reduce the headlights flicker at night also. Just type in FARAD in e-bay search under car stereo. The caps can be dangerous when charged up . They can discharge VERY high amps if shorted out as their ESR is very low. 1- 30 Farads can be found, and they are not cheap either. I have seen a bank of them even crank over a 8 cylinder engine. Try that with 100,00 uF Cap. "Dr. Death" wrote in message ... if your peaks are up that equates to higher (but probably not much like you said) average output. BUT, you brought up a good point about the clipping "Frank Gilliland" wrote in message ... In , "Dr. Death" wrote: snip So you agree, it would work for ssb I agree that adding a cap across the power leads will help keep the peaks up, and that's assuming the amp isn't clipping on the peaks. IOW, it should improve the audio quality when using a less-than-perfect power supply, just as if it were an audio amp. What it -won't- do is improve your average output power by any significant margin. -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
#12
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In pP6Bb.465454$HS4.3620546@attbi_s01, "MasterCBer" wrote:
I have used the BIG caps as used on the audio amps on my RF power amp and it did help on the current spikes that was needed on SSB peaks. Without the Cap, the voltage could drop to 10.5 volts on current peaks measured at the amp, now it might go to 12 - 12.5 volts only rising to the supplied 13.8 volts in the system. It help to reduce the headlights flicker at night also. Just type in FARAD in e-bay search under car stereo. The caps can be dangerous when charged up . They can discharge VERY high amps if shorted out as their ESR is very low. 1- 30 Farads can be found, and they are not cheap either. I have seen a bank of them even crank over a 8 cylinder engine. Try that with 100,00 uF Cap. There's that "more power" attitude that drives an amp junkie's cravings. You need to learn what ESR is and how different it is for different types of capacitors (and batteries, too). For example, I have seen a car battery turn over an 8 cylinder engine, but that doesn't mean it has a low ESR. It just means that it can hold a big charge and has almost nothing to do with ESR. When all you want to do is to keep the peaks up in an SSB linear you don't need a charge so large that it will turn over an engine. That's called "overkill". ============= "...but I admitted I was wrong, Like a man! Something you and QRM have a problem with. You guys are wrong and you both know it and are both too small to admit it." ---- Twistedhed ---- ============= -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
#13
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![]() "Dr. Death", Using a very large capacitor to keep the instantanious voltage from dropping very much certainly will work. The question is, how much benefit is going to be realized from that? The answer is, not very much. Now, balance that 'not very much' with the cost of those very large capacitors and draw your own conclusions. Personally, I think it's a waste of time, just isn't worth it. It usually means that you're trying to 'squeeze' more out of something than it was designed to do to start with, which is a kinda silly thing to do. If you want to try it, then have at it. I'd rather waste my money on other things... 'Doc |
#14
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On Mon, 8 Dec 2003 03:23:00 -0600, "Dr. Death"
wrote: I noticed that a lot of high end auto audio systems use a capacitor in series with the main power lead to the amplifies so the amp hits harder. Could this same principle be applied to ssb, I think it can. place a 1 farad audio cap inline with the power lead to say a Texas star dx1600 and you run the rig on ssb the cap will discharge under peak load giving you a higher average output. Any comments? (and I mean REAL comments) A one farad capacitor can only supply one amp for one second at one volt. Hardly worth the expense. It can only prevent a voltage drop on the first few peaks of a SSB modulated signal. It's usefulness would be almost totally drained after speaking just one appropriate word, pointless. |
#16
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actually it was just food for thought, with all the flaming going on I
thought I would introduce a subject that would produce more thinking than fighting. "'Doc" wrote in message ... "Dr. Death", Using a very large capacitor to keep the instantanious voltage from dropping very much certainly will work. The question is, how much benefit is going to be realized from that? The answer is, not very much. Now, balance that 'not very much' with the cost of those very large capacitors and draw your own conclusions. Personally, I think it's a waste of time, just isn't worth it. It usually means that you're trying to 'squeeze' more out of something than it was designed to do to start with, which is a kinda silly thing to do. If you want to try it, then have at it. I'd rather waste my money on other things... 'Doc |
#17
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Well lets see here DOC and Frank
Have you tried a Large farad cap on your amp? I thought not. So unless you have then don't cut it. Frank you need to learn what ESR is you ****en dum ass. These cap have a very LOW ESR as I said in my first post I or do you not read very well. Doc , it works, and you know it could unless your a Dumass also. so why put your little ****ty wisdom comments in Sure its costs money, but to me running several alternators and a big amp just to say Audio is a waste of money to me. We all have our quirks. Why do CBERs spend good money just to raise the power out on a 4 watt rig to 7 watts and think its walking the dog, cant tell it on the receiving end. O well beleave what you want. He asked a question and I gave a good answer, it works. Then here comes all the so called Brains on this group. Hell I dough if they really do anything with there's, just sent on their ass and tell every one else how smart they think they really are . SO called DOC is really a flunky, and Frank hell he must work for some portal potty outfit. Dam It would be nice if they could just give a answer without trying to act as if they are the only ones in the world with knowledge. **** them two. Frank go and get one of those caps there are very LOW "Frank Gilliland" wrote in message news ![]() In , wrote: On Mon, 8 Dec 2003 03:23:00 -0600, "Dr. Death" wrote: I noticed that a lot of high end auto audio systems use a capacitor in series with the main power lead to the amplifies so the amp hits harder. Could this same principle be applied to ssb, I think it can. place a 1 farad audio cap inline with the power lead to say a Texas star dx1600 and you run the rig on ssb the cap will discharge under peak load giving you a higher average output. Any comments? (and I mean REAL comments) A one farad capacitor can only supply one amp for one second at one volt. Hardly worth the expense. It can only prevent a voltage drop on the first few peaks of a SSB modulated signal. It's usefulness would be almost totally drained after speaking just one appropriate word, pointless. Then there is not much point in using them in any kind of DC power supply, is there? Of course there is. Do the math, Tnom: A good car battery has, on the average, an source impedance of around 0.01 ohms (dropping 1 volt per 100 amps, which is a darn good battery). Ten feet of #8 AWG has a DC resistance of 0.0063 ohms, and we'll just assume that the negative lead is grounded at 0 ohms. So the total source impedance at the input of the amp is 0.0163 ohms. Now take an amp that can do 500 watts PEP. Assuming 50% efficiency, that means it can draw a maximum of 79.4 amps @ 12.6 volts. But since the source impedance is 0.0163 ohms, the voltage is going to drop 1.3 volts on the peaks, reducing the peak output by 50 watts or more. This is a type of soft-clipping and can result in some significant AF -and- RF distortion. And that's not considering the temperature coefficient of copper, which shows more resistance as it warms up from carrying lots of current, making the situation worse. Adding caps at the power input leads of the amp can significantly reduce the source impedance of the power supply. It -can't- provide more power than the supply is capable of providing, but it -can- smooth the voltage ripple just like in any other type of power supply. And what if the vehicle is running? Do the math: If you have a 100 amp alternator (at 13.8 volts), it has a source impedance of .138 ohms, which is significantly higher than the battery, so it's not going to be much help. In fact, because it's going to be so heavily loaded, it's going to introduce some ripple into the power lines, ripple that can be reduced by using caps at the input of the amp. How much capacitance is needed? There is no easy equation. There are a number of factors, such as the source resistance of the battery and alternator, resistance of the wire, ESR of the capacitors, average modulation percentage, PEP watts, etc, etc. Because of the very low impedance required by the amp, low ESR is paramount. Despite the advertised claims, the 'monster' caps usually have an ESR of several ohms, much higher than is usable. Computer-grade electrolytics have a much lower ESR. Using many smaller caps in parallel is better than one big cap because the ESR is much lower. Those are just a few things to consider. But the general rule is to keep adding caps until they no longer make any improvement. I'm really suprised, Tnom. After all the times you have shot your mouth off and been proven wrong on technical topics, you -still- haven't learned to think before you speak. Maybe next time. ============= "...but I admitted I was wrong, Like a man! Something you and QRM have a problem with. You guys are wrong and you both know it and are both too small to admit it." ---- Twistedhed ---- ============= -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
#18
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![]() "Dr. Death", Good idea. 'Doc |
#19
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snip
A one farad capacitor can only supply one amp for one second at one volt. Hardly worth the expense. It can only prevent a voltage drop on the first few peaks of a SSB modulated signal. It's usefulness would be almost totally drained after speaking just one appropriate word, pointless. Then there is not much point in using them in any kind of DC power supply, is there? Of course there is. Do the math, Tnom: Oranges and apples............... P.S. you are a idiot for even equating the two A good car battery has, on the average, an source impedance of around 0.01 ohms (dropping 1 volt per 100 amps, which is a darn good battery). Ten feet of #8 AWG has a DC resistance of 0.0063 ohms, and we'll just assume that the negative lead is grounded at 0 ohms. So the total source impedance at the input of the amp is 0.0163 ohms. Now take an amp that can do 500 watts PEP. Assuming 50% efficiency, that means it can draw a maximum of 79.4 amps @ 12.6 volts. But since the source impedance is 0.0163 ohms, the voltage is going to drop 1.3 volts on the peaks, reducing the peak output by 50 watts or more. This is a type of soft-clipping and can result in some significant AF -and- RF distortion. And that's not considering the temperature coefficient of copper, which shows more resistance as it warms up from carrying lots of current, making the situation worse. Adding caps at the power input leads of the amp can significantly reduce the source impedance of the power supply. It -can't- provide more power than the supply is capable of providing, But for how long........."Do the math" but it -can- smooth the voltage ripple just like in any other type of power supply. And what if the vehicle is running? Do the math: If you have a 100 amp alternator (at 13.8 volts), it has a source impedance of .138 ohms, which is significantly higher than the battery, so it's not going to be much help. In fact, because it's going to be so heavily loaded, it's going to introduce some ripple into the power lines, ripple that can be reduced by using caps at the input of the amp. How much capacitance is needed? There is no easy equation. There are a number of factors, such as the source resistance of the battery and alternator, resistance of the wire, ESR of the capacitors, average modulation percentage, PEP watts, etc, etc. Because of the very low impedance required by the amp, low ESR is paramount. Despite the advertised claims, the 'monster' caps usually have an ESR of several ohms, much higher than is usable. Computer-grade electrolytics have a much lower ESR. Using many smaller caps in parallel is better than one big cap because the ESR is much lower. Those are just a few things to consider. But the general rule is to keep adding caps until they no longer make any improvement. I'm really suprised, Tnom. After all the times you have shot your mouth off and been proven wrong on technical topics, you -still- haven't learned to think before you speak. Maybe next time. One thing I am not surprised at........You will ignore the facts, like you normally do to flame the group or express your pseudo theory. Yeah...Right, A few farads will make a justifiable difference. You're to funny. |
#20
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In 9McBb.1407$8y1.13274@attbi_s52, "MasterCBer" wrote:
Well lets see here DOC and Frank Have you tried a Large farad cap on your amp? I use caps on just about everything mobile. They work great to get the low-end from an audio amp. No, I don't run an RF amp, base or mobile. Yes, I have intalled a few; and yes, they do run better with a big cap on the power leads. By 'better' I mean that the audio is cleaner and IMD is reduced. I thought not. No you didn't. So unless you have then don't cut it. Frank you need to learn what ESR is you ****en dum ass. These cap have a very LOW ESR as I said in my first post I or do you not read very well. From Cornell Dubilier: 381LX473M016A452 47000 uFd @ 16 VDC 0.017 ohms @ 120 Hz 0.013 ohms @ 20 kHz Now you can probably find farad-sized electrolytics -advertised- for lower ESR, but they don't tell you the frequency or conditions under which that ESR was measured. There are engineering standards for measuring such things as ESR. Industry has to deal with these standards all the time. But as long as these caps are not marketed for industrial use the manufacturers can declare an ESR that is measured in any way they want, even by measuring the cap in a series resonant circuit with a high impedance source. IOW, it's a lot of hype, just like the ridiculous gain figures that are advertised for some CB antennas. About the lowest -real- ESR you will find among those ultra-high-density caps is about 0.2 ohms, and it will cost you most of a paycheck (two or three paychecks if you have a McJob). The problem here is one that has existed since the first capacitor was invented: There is a tradeoff between charge density (uF per cubic inch) and ESR. Whenever the physical size of a capacitor gets too large, it usually dictates a different type of capacitor. A 1 farad air capacitor would have an extremely low ESR, but it would probably be as big as an aircraft carrier (which would introduce other problems, but those are ignored for the sake of this example). If it was an oil/paper capacitor it might be as big as a house. Even an aluminum electrolytic of 1 farad would still be quite large for a mobile application. So these monster caps are built with a different type of electrolytic process, one that packs more farads into a smaller space, but at the expense of increased dielectric absorption/hysteresis, i.e, a higher ESR. Put more simply, if these big caps were as good as the advertisers claim them to be, they would have replaced aluminum electrolytics a long, long time ago. They haven't. Put even more simply, if it looks too good to be true, it probably is. If you don't believe me, buy one and measure it yourself. You will need a very low impedance source and load, then measure the difference in ripple voltage on a scope. Post the results. And just to make my point about smaller caps in parallel being better than one big cap: 381LX472M016H012 4700 uFd @ 16 VDC 0.113 ohms @ 120 Hz 0.085 ohms @ 20 kHz Put ten of the 4700 uFd caps in parallel and you have 47000 uFd, but with an ESR of 0.0113 ohms @ 120 Hz and 0.0085 @ 20 kHz, which is better than the 47000 uFd capacitor. This value would drop the source impedance (in my example from the previous post) from 0.0163 ohms to 0.0067 ohms, meaning the voltage will only drop 0.53 volts on a peak. So in this example, the caps give back three-quarters of the power that is missing from the peaks when run without the caps. Compare that to any size cap with an ESR of 0.2 ohms. ============= "...but I admitted I was wrong, Like a man! Something you and QRM have a problem with. You guys are wrong and you both know it and are both too small to admit it." ---- Twistedhed ---- ============= -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
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