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Old Mar 16, 2011, 05:55 PM
...just an earth bound misfit
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I got a chance to run Hugo's 5.8 GHz pinwheels through the our new Agilent 9912A FieldFox RF analyzer today and got the attached results for VSWR. Any comments?

Unfortunately we don't have the network analyzer or vector voltmeter "option" licenses yet, just the CAT (cable/antenna test) and SA (spectrum analyzer) .
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Old Mar 16, 2011, 06:46 PM
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That's impressive for 5.8GHz. Looks like the elements were a bit short.

Mine aren't nearly as neat as his for sure. I also like to run a small section of coaxial cable to get the antenna away from the transmitter. The Fresnel zone is very small at 5.8GHz.

-Alex
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Old Mar 16, 2011, 07:06 PM
...just an earth bound misfit
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Unfortunately the analyzer tops out at 6 GHz so I couldn't run it much wider, but it looks like 1.5 might be as good as it gets. I was lucky to track down an adapter kit that could handle RP-SMA to N-type today, let alone feed lines, but it is definitely very sensitive to objects (like fingers) in close proximity.

Here's the 5.4-6.0 GHz VSWR sweep.
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Old Mar 16, 2011, 08:59 PM
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Thx for sharing that with us.

1.5 is really not bad considering the frequency, a different after-shave and you might get different results
Did you test both?

Next ones will have a small coax (1/2 wave length)
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Old Mar 16, 2011, 09:19 PM
...just an earth bound misfit
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Hey Hugo, thanks for sharing the antennas with me, I just wish I had the license codes to enable the network analyzer so I could have plotted an impedance sweep on a Smith chart.

Post #226 had two attached images, one for each antenna's VSWR. The better of the two ranged from 1.5-1.8 and the other from 1.7-2.0

Next step is to get a regulator fro my RangeVideo tx and do some coastal ground testing. I might build a helical antenna for that work as I have some nice LOS shots ranging from 6-18 km.
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Old Mar 17, 2011, 07:29 AM
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Quote:
Originally Posted by Hugeone View Post
Thx for sharing that with us.

1.5 is really not bad considering the frequency, a different after-shave and you might get different results
Did you test both?

Next ones will have a small coax (1/2 wave length)
Or humidity will even change it. I bet a short run of coaxial cable will lower SWR due to the antenna being farther away from the test device. I make my 5.8 GHz antennas with about 1 wavelength or so coaxial and the antenna is formed into it. I also make it so the feed acts as a balun

-Alex
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Old Mar 17, 2011, 03:58 PM
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Produced a couple of these great antennas at work today



Thanks again for your great instructions Alex!


David
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Old Mar 17, 2011, 10:11 PM
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Those look fantastic.
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Old Mar 18, 2011, 03:27 PM
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DODOLAND
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Hi Alex,
Can you tell me if I can use RG58 50ohmn coax to connect antenna to the RX on 433mhz.Its a bit hard for me to find RG174 for the moment.I just want to make an extension.

Thanks,
Anthony.
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Old Mar 18, 2011, 06:51 PM
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Yes RG58 will work. In fact, I recommend it over Rg174.

-Alex
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Old Mar 18, 2011, 08:26 PM
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My skew planar wheel for my 2.4Ghz vrx.
I have used a length (1/2wave length)) of semirigid coax and 1.0mm mig wire.
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Old Mar 18, 2011, 08:40 PM
...just an earth bound misfit
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Quote:
Originally Posted by IBCrazy View Post
Or humidity will even change it. I bet a short run of coaxial cable will lower SWR due to the antenna being farther away from the test device. I make my 5.8 GHz antennas with about 1 wavelength or so coaxial and the antenna is formed into it. I also make it so the feed acts as a balun

-Alex
The result with a random 50cm (~10 lambda) SMA feed line was a bit better.
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Old Mar 19, 2011, 08:54 AM
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Ask for inspection :)

Do you think this looks good?



Thanks
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Old Mar 19, 2011, 09:59 AM
...just an earth bound misfit
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doh.
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Last edited by Dirt-Torpedo; Mar 19, 2011 at 10:05 AM. Reason: duplicate
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Old Mar 19, 2011, 10:04 AM
...just an earth bound misfit
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I expect you'll have some non-ideal behaviour due to the proximity of the coax shield to the leg of the element that it is taped to. This could be modelled or measured but you need to have the tools and know how to use them...
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