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#1
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K7ITM wrote:
Field strength alone is not acceptable to me as a means to adjust an antenna load to a transmitter, ... Doesn't being located in the near field introduce a measurement error? -- 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 =---- |
#2
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Depends on what you mean by error. Is it a linear system? If the near
field strength increases with no change in the radiating structure itself (and propagation is stable, etc.), does the far field not increase by the same ratio? But of course, with a repositionable (rotatable) directional antenna, it's pretty hard to calibrate the FSM in a meaningful way since the antenna system changes (quite a lot, with respect to the FSM) as you rotate it, so you don't know from one time to the next that you have the RIGHT field strength. I'd (ideally) like to know that the transmitter is properly adjusted to output a clean signal, and that the antenna system presents the proper load to the transmitter, AND that the antenna system is radiating like I'd like it to. The "SWR meter" is one component that helps me, but with only one of those tasks. (And yes, it's fine with me if you care also about the SWR on your 450 ohm balanced line...there may also be good reason for wanting to know that.) Cheers, Tom PS--Frank, if you look back in the archives from this group, you'll find directional couplers (of the sort that measure the line at a single point) explained in great detail with four-part harmony and the whole nine yards. Go study them and you may understand why calibration is important. |
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