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#11
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"K9SQG" wrote in message ... There are several reasons why maximum field strength and minimum SWR don't occur at the same points, necessarily. The field strength can be considered part of the "efficiency" of the overall system. SWR just relates to the match between the feedline and the coax. Think of the dummy load example; it might exhibit close to a 1:1 SWR but radiates little power. A dummy load is also physical proof of the existence of an isotropic radiator (albeit a rather poor radiator g). Ed WB6WSN |
#12
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"nathan" wrote
I have always heard that this is true, and that I should tune antennas for maximum field strength and not for minimum SWR. Why wouldn't they occur at the same time? .................................................. ...... Minimum SWR informs you your transmitter is loaded with the nearest possible impedance to 50 ohms. Maximum field strength informs you your transmitter is sending out maximum possible power. There's no way of knowing whether or not the two conditions coincide. It may occur at maximum field strength that the load on the transmitter causes distortion and poor efficiency in the PA with excessive internal volts or amps or watts. So to avoid flogging the PA or power supply to an early death you should always tune up to minimum, preferably zero SWR. You have to balance the probabilities. What are the chances of winning the contest before the PA issues smoke. ---- Reg, G4FGQ |
#13
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Two different issues Reg, Does a tuner change the SWR of an antenna? Or
does it simply transform an impedence to one that makes the transmitter happy? Will the maximum field strength coincide with 1:1 SWR at the tuner in all cases? With my old DX-100 with Pi net output (read not stuck with a 50 ohm output) I tuned for the max field strength that did not exceed the current ratings of the 6146's. I will admit that in a contest the rule changed to "Tune for maximum smoke and replace all charred components". Having an SWR bridge is like wearing dark trousers, if you pee your pants, no one notices - but it gives you a warm feeling. As soon as I become dictator of the world, I am outlawing them... "Reg Edwards" wrote in message ... "nathan" wrote I have always heard that this is true, and that I should tune antennas for maximum field strength and not for minimum SWR. Why wouldn't they occur at the same time? .................................................. ..... Minimum SWR informs you your transmitter is loaded with the nearest possible impedance to 50 ohms. Maximum field strength informs you your transmitter is sending out maximum possible power. There's no way of knowing whether or not the two conditions coincide. It may occur at maximum field strength that the load on the transmitter causes distortion and poor efficiency in the PA with excessive internal volts or amps or watts. So to avoid flogging the PA or power supply to an early death you should always tune up to minimum, preferably zero SWR. You have to balance the probabilities. What are the chances of winning the contest before the PA issues smoke. ---- Reg, G4FGQ |
#14
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Two different issues Reg, Does a tuner change the SWR of an antenna? Or
does it simply transform an impedence to one that makes the transmitter happy? Will the maximum field strength coincide with 1:1 SWR at the tuner in all cases? With my old DX-100 with Pi net output (read not stuck with a 50 ohm output) I tuned for the max field strength that did not exceed the current ratings of the 6146's. I will admit that in a contest the rule changed to "Tune for maximum smoke and replace all charred components". Having an SWR bridge is like wearing dark trousers, if you pee your pants, no one notices - but it gives you a warm feeling. As soon as I become dictator of the world, I am outlawing them... "Reg Edwards" wrote in message ... "nathan" wrote I have always heard that this is true, and that I should tune antennas for maximum field strength and not for minimum SWR. Why wouldn't they occur at the same time? .................................................. ..... Minimum SWR informs you your transmitter is loaded with the nearest possible impedance to 50 ohms. Maximum field strength informs you your transmitter is sending out maximum possible power. There's no way of knowing whether or not the two conditions coincide. It may occur at maximum field strength that the load on the transmitter causes distortion and poor efficiency in the PA with excessive internal volts or amps or watts. So to avoid flogging the PA or power supply to an early death you should always tune up to minimum, preferably zero SWR. You have to balance the probabilities. What are the chances of winning the contest before the PA issues smoke. ---- Reg, G4FGQ |
#15
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w4jle wrote: " Does a tuner change the SWR of an antenna? Or does it simply transform an impedence to one that makes the transmitter happy? Will the maximum field strength coincide with 1:1 SWR at the tuner in all cases?" 1. A tuner doesn't change the SWR of an antenna. It will change the SWR of the system to something the transmitter 'likes'. 2. In all cases? Probably not. In 'most' cases? A definite maybe. 'Doc |
#16
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preferably zero SWR.
Reg, G4FGQ How do you get that mr. snotty? The closest I am able to get is 1 or 1:1 Care to enlighten us dumbells? BUm |
#17
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On Thu, 20 Nov 2003 12:47:00 -0500, "w4jle" W4JLE(remove this to
wrote: Having an SWR bridge is like wearing dark trousers, if you pee your pants, no one notices - but it gives you a warm feeling. Not having a SWR meter merely means you can't feel the warm sensation for the same circumstances ... which may lead to everyone noticing. (An example of how similes fail.) 73's Richard Clark, KB7QHC |
#18
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I'll allow your fellow amateurs to judge who's the dumbell.
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