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#11
April 15th 05, 08:19 PM
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Because it is dependent on any "lumped" inductive or capacitive reactances
present... chuck a coil or capacitance (reactance) in the structure of the antenna, then replot with a field strength meter... Regards, John "Henry Kolesnik" wrote in message ... How does a mismatch affect the radiation pattern? tnx -- 73 Hank WD5JFR "John Smith" wrote in message news  I could be mistaken, however, I think the radiation patten (and receive patten) would, at least, be slightly affected by a mis-match... whether this would justify going to extreme means of correction is debatable... Regards, John "Henry Kolesnik" wrote in message m... I need a sanity check. I fellow told me he was getting a balun to get a better match between his receiver and antenna to get a better signal to noise ratio. I told him he was wasting his time and money because a better match increases transfer of both signal and noise. But since he already can hear the signal he doesn't need any more. Now if he was to get a more directional antenna he would get a reduction in noise from the undesired direction. -- 73 Hank WD5JFR |
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#12
April 15th 05, 08:24 PM
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Henry Kolesnik wrote:
How does a mismatch affect the radiation pattern? Please define "mismatch". An unbalanced 50 ohms to balanced 50 ohms could conceivably be defined as a "mismatch". -- 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! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
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#13
April 15th 05, 08:48 PM
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"John Smith" said - I could be mistaken, however, I think the radiation patten (and receive patten) would, at least, be slightly affected by a mis-match... whether this would justify going to extreme means of correction is debatable... ============================== John, your level of analysis is far, far above that justified by the simplicity of the problem(s). Just get some wire in the air and see how well it works. ---- Reg, G4FGQ |
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#14
April 15th 05, 09:50 PM
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LOL! Sometimes I forget Reg--sorry grin
Warmest regards, John "Reg Edwards" wrote in message ... "John Smith" said - I could be mistaken, however, I think the radiation patten (and receive patten) would, at least, be slightly affected by a mis-match... whether this would justify going to extreme means of correction is debatable... ============================== John, your level of analysis is far, far above that justified by the simplicity of the problem(s). Just get some wire in the air and see how well it works. ---- Reg, G4FGQ |
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#15
April 16th 05, 03:26 PM
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How does a mismatch affect the radiation pattern?
tnx ..... It doesn't. I don't consider unbalanced, the same as mismatched, to answer Cecils question. Feedline radiation can effect the pattern due to a lack of balun, etc, but thats not the same thing as an impedance mismatch. Also...Antenna "loading" is not the same as antenna "matching". Many short verticals need both... MK |
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#16
April 16th 05, 04:11 PM
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Maybe I have a misunderstanding. I see a "mismatch" as being caused by only
two factors, either an uncompensated reactance--or, as Cecil mentioned, feeding a bal/unbal antenna with the wrong feedline. Indeed, any feedline can simply be analyzed as a series of lumped reactances--inductive and capactitive. How should I be viewing this? Regards, John wrote in message oups.com... How does a mismatch affect the radiation pattern? tnx ..... It doesn't. I don't consider unbalanced, the same as mismatched, to answer Cecils question. Feedline radiation can effect the pattern due to a lack of balun, etc, but thats not the same thing as an impedance mismatch. Also...Antenna "loading" is not the same as antenna "matching". Many short verticals need both... MK |
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#17
April 16th 05, 04:30 PM
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Errr, let me be a bit more specific...
The "beam width" of a quarter-wave has a very wide "acceptance ratio" and grabs much more reflection from the ionosphere--a half-wave has a much narrower beam width--it is a "quieter" antenna, but, grabs more of the signal I am after... At least, it appears like that... A five-eights-wave has even a lower beam width--these three antennas, because of length differences, exhibit differing reactances, when these reactances are cancelled (such as using an L-Match) they become "matched"--right? Of course, this ignores conductor resistance, and takes for granted the antenna is being fed at the proper point... Regards, John "John Smith" wrote in message ... Maybe I have a misunderstanding. I see a "mismatch" as being caused by only two factors, either an uncompensated reactance--or, as Cecil mentioned, feeding a bal/unbal antenna with the wrong feedline. Indeed, any feedline can simply be analyzed as a series of lumped reactances--inductive and capactitive. How should I be viewing this? Regards, John wrote in message oups.com... How does a mismatch affect the radiation pattern? tnx ..... It doesn't. I don't consider unbalanced, the same as mismatched, to answer Cecils question. Feedline radiation can effect the pattern due to a lack of balun, etc, but thats not the same thing as an impedance mismatch. Also...Antenna "loading" is not the same as antenna "matching". Many short verticals need both... MK |
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#18
April 16th 05, 05:03 PM
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"John Smith" wrote
The "beam width" of a quarter-wave has a very wide "acceptance ratio" and grabs much more reflection from the ionosphere--a half-wave has a much narrower beam width--it is a "quieter" antenna, but, grabs more of the signal I am after... _____________ A 1/2-wave VHF/UHF vertical has more gain at lower elevation angles than a 1/4-wave, but that may not usefully improve the SNR of the system. Most of the noise power in these antennas doesn't arrive from higher angles anyway, because those freqs don't reflect well from the ionosphere. RF |
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#19
April 16th 05, 05:33 PM
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No. Feeder radiation has *nothing* to do with impedance
matching. Zero. Nada...Zilch. Ever!...You can have a perfect 1:1 match, and still have feedline radiation. Or you can have a horrible impedance mismatch, and have very little feeder radiation. Feeder unbalance, lack of baluns, chokes, etc, etc, should never be confused with impedance matching. I don't think the term "mismatch" should be applied to a lack of balance, etc...If you tell me you have a mismatch, I'll always assume you mean impedance. Anyway, no matter my views... Impedance mismatch will never change the pattern of the antenna. For practical purposes, it's the same as raising or lowering power to the antenna. If you run 50 more watts to an antenna, it's pattern does not change. Ditto, if you run 50 less...MK |
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#20
April 16th 05, 07:06 PM
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huh? If you have an impedance mismatch, you are NOT feeding the antenna at
the proper point, or with the proper ohm line, or without a proper matching circuit! Either one of these will exhibit some type of reactance! OR! OMG! My "knowledge"/thinking is in error! ???? Regards, John wrote in message ups.com... No. Feeder radiation has *nothing* to do with impedance matching. Zero. Nada...Zilch. Ever!...You can have a perfect 1:1 match, and still have feedline radiation. Or you can have a horrible impedance mismatch, and have very little feeder radiation. Feeder unbalance, lack of baluns, chokes, etc, etc, should never be confused with impedance matching. I don't think the term "mismatch" should be applied to a lack of balance, etc...If you tell me you have a mismatch, I'll always assume you mean impedance. Anyway, no matter my views... Impedance mismatch will never change the pattern of the antenna. For practical purposes, it's the same as raising or lowering power to the antenna. If you run 50 more watts to an antenna, it's pattern does not change. Ditto, if you run 50 less...MK |
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