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AIM4170 Presentation -- open-wire feeder TDR scan
I have added a further update to the AIM4170 Presentation, showing a TDR
scan on an open-wire feeder. Go to: http://homepage.ntlworld.com/wadei/aim4170.htm then click on the link "AIM4170 PowerPoint Presentation". New slides 72, 73 and 74 show clearly that although Zo = the calculated free space value at the antenna feedpoint, it is otherwise considerably affected by the feeder’s proximity to ground and other objects. Zo actually falls as the feeder descends from the shack window to the garage, remains more-or-less constant as it passes over the garage roof, and only begins to increase again as it traverses the hedge and passes through the tree. Note also that the impedance decreases slightly where the feeder narrows at the antenna feedpoint. Yet another example of the incredible versatility of the AIM4170. -- 73 Ian, G3NRW The AIM4170 Antenna Analyzer: http://homepage.ntlworld.com/wadei/aim4170.htm |
#2
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AIM4170 Presentation -- open-wire feeder TDR scan
Ian Wade G3NRW wrote: I have added a further update to the AIM4170 Presentation, showing a TDR scan on an open-wire feeder. Go to: http://homepage.ntlworld.com/wadei/aim4170.htm then click on the link "AIM4170 PowerPoint Presentation". New slides 72, 73 and 74 show clearly that although Zo = the calculated free space value at the antenna feedpoint, it is otherwise considerably affected by the feeder’s proximity to ground and other objects. Zo actually falls as the feeder descends from the shack window to the garage, remains more-or-less constant as it passes over the garage roof, and only begins to increase again as it traverses the hedge and passes through the tree. Note also that the impedance decreases slightly where the feeder narrows at the antenna feedpoint. Yet another example of the incredible versatility of the AIM4170. I'm surprised that there were no FUs to this (at least in ukra). This looks like a seriously useful bit of kit for the antenna experimenter, but whether I could personally justify one for my string-and-sealing-wax approach to short wire antennas is questionable. Although this device means one could fine-tune one's antenna, the one thing that affects very nearly every Amateur is the ground around their installation, probably up to 10 lambda before the various fields and rays begin to sort themselves out. There seems to be no equivalent piece of kit that would enable such an assessment to be made or its effect on the station's performance to be estimated. I guess most of us take the view that one lives with what one has, and can't do much about it anyway. -- Spike |
#3
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AIM4170 Presentation -- open-wire feeder TDR scan
On Jun 13, 12:19*pm, Spike wrote:
I'm surprised that there were no FUs to this (at least in ukra). This looks like a seriously useful bit of kit for the antenna experimenter, but whether I could personally justify one for my string-and-sealing-wax approach to short wire antennas is questionable. I had a quick look at this piece of equipment, but couldn't see it offering anything more than the MRS MiniVNA, which is a two port device and a more versatile instrument. (A one port device is useless for setting up filters etc.) |
#4
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AIM4170 Presentation -- open-wire feeder TDR scan
On Jun 13, 1:23*pm, Brian Morrison wrote:
And it's a bit more future proof since it has a USB connection rather than RS-232. I don't think RS232 is going to die just yet. It's still easy to cater for, but as you say, USB is a lot more convenient since just sbout every PC these days has them. However I'm always cautious about anything software driven becoming obsolete. Hence I also keep a Palstar ZM30 around for HF work, that doesn't require a PC, but still gives me all the relevent data for antenna work. And after all that, I still insist on a final tune up with a field strength meter ;-) The mini VNA being a two port device is great for making high/low /bandpass./notch filters and instant seeing the response. You can line up IF xtal filters etc. Very versatile. |
#5
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AIM4170 Presentation -- open-wire feeder TDR scan
HAGGIS KILT Inscribed thus:
2446 lines of "bla" Plonk ! -- Best Regards: Baron. |
#6
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It is a nice post and good discussion and i had been looking for some information and it is a nice post for this point of view.
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