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#41
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Reg Edwards wrote:
If a conjugate match matters two hoots, or is involved in the slightest way with the design of power amplifiers or any other sort of amplifier, why don't tube manufacturers state the internal resistance or impedance in tube date sheets? So I guess you just connect your tubes or transistor finals directly to the coax? I mean, since it doesn't matter... Tom K0TAR |
#42
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In article ,
Tam/WB2TT wrote: [...] When device people talk about "matching", they mean matching the load to what the transistor wants to see, which is not the conjugate of the output impedance. Actually, in this case, I was speaking of matching the transmitter's output to the load. The transmitter already contains gawd knows what L and C components etc. The OP has a completed transmitter and a hunk of wire. If he matches the wire to what the transmitter wants to see, the transmitter will be happy. If he causes a reactive current to flow that the designer did not design for he will cause added heating in the output device. If the designer did a good job, the transmitter will protect its output devices and thus end up producing less power. Also if he makes the real component of the impedance vary from what the designer intended, the output power will decrease. Which direction gets limited by the Vcc and which by the protection circuit depends on the collection of Ls and Cs inside the transmitter. -- -- forging knowledge |
#43
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Ken Smith wrote:
Now lets assume that you slightly decrease the resistance. Since we are assuming that this is a well designed case, we can assume that the designer took steps to ensure that the output devices would be protected from excess currents. Let's assume the designer is an amateur who didn't provide any protection for his tube's output. The lower the resistive load, the more current the output device draws until it fails. What is the output impedance of the device? -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
#44
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Rich Grise wrote:
Evidently, the guy's never tuned up a 40 meter pi-net output transmitter. ;-) If that's not impedance matching, I don't know what it is! (Oh, "Load line" matching? What are the two parameters of the load line? Voltage and Current, right? What's the slope of the load line? Impedance!) And there's the catch. If the load line is the source impedance, the load (not the designer) effects the source impedance. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
#45
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Reg Edwards wrote:
If a conjugate match matters two hoots, or is involved in the slightest way with the design of power amplifiers or any other sort of amplifier, why don't tube manufacturers state the internal resistance or impedance in tube date sheets? When I first became a ham, transmitters didn't have any protection at all. They would keep putting out more and more power until the final or power supply got too hot. My 6L6 went out during a contest in the 50's. All I had to replace it with was a metal 6V6. What's the source impedance of a 6V6 plugged into a 6L6 socket? -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
#46
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The phrase "output impedance" in connection with amplifiers is ambiguous and
likely to result in arguments. The correct description is "internal impedance" or "internal resistance" and should always be used. ---- Reg. |
#47
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Ken Smith wrote:
If you then put in the output device protection they didn't include, you end up with the matching as I explained elsewhere. SWR foldback is part of impedance matching? -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
#48
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"Reg Edwards" wrote in
message ... The phrase "output impedance" in connection with amplifiers is ambiguous and likely to result in arguments. I suppose the same could be said of any block that is susceptible to having some feedback put around it. Therefore the term "output impedance" should never be used at all. And of course, any term that could, or has ever been known to lead to an argument, with any uninformed person that might come along, should be eliminated from our vocabulary. Uuugh. Mmmmph. Me drag woman to cave by hair. The correct description is "internal impedance" or "internal resistance" and should always be used. Nonsense. If I wanted to speak of an impedance inside of some circuit, I might loosely speak of it as "internal", but in any useful discussion, it would be spoken of as either an output impedance or an input impedance, and, with most people I have such discussions with, there would be no need to add that some unknown additional feed- back not part of the present discussion could alter the observable impedance. I hope your post was a troll. -- --Larry Brasfield email: Above views may belong only to me. |
#49
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I read in sci.electronics.design that gwhite wrote
(in ) about '1/4 vs 1/2 wavelength antenna', on Fri, 25 Feb 2005: I'm sorry, but they are not. Nor are any power amps that I know of. Efficiency (and thus necessarily output swing) is what matters for power amps. To maximize swing requires load line matching, not impedance matching. What is a 'load line'? A straight line on an I/V graph? What does the gradient of that line represent? -- Regards, John Woodgate, OOO - Own Opinions Only. The good news is that nothing is compulsory. The bad news is that everything is prohibited. http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk |
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