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Ceengland
Joined: 11 Oct 2020
Posts: 391
Location: MS
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 Posted: Sat Oct 24, 2020 12:34 pm Post subject: ADS-B and Transponder antenna... |
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On Thu, Oct 1, 2020 at 8:59 AM andymeyer <meyerkc135(at)gmail.com (meyerkc135(at)gmail.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: "andymeyer" <meyerkc135(at)gmail.com (meyerkc135(at)gmail.com)>
So, all this chatter about the ELT antennas got me thinking about the ADS-B antenna I made. I dove into the math, made some estimates, and designed two on Upverter and had parts made. I got luck in that my SlimJim ADS-B antenna has picked up airborne traffic over 100 miles away connected to a Stratux (I have both SDR radios tied into a single antenna - criminal - I know, but it works and it's small and light.)
Attached are the layouts of the two antennas and links to the actual designs on Upverter.
I had 5 of each made. Anyone interested in testing and sharing data - maybe make this a shared design as well. Cost is just a few bucks.
Slim Jim: https://upverter.com/eda/#tool=pcb,designId=1d1c59be761e9901
DiPole: https://upverter.com/eda/#tool=pcb,designId=9eb3fbd043861e96
(Upverter is a pretty awesome cloud based schematic and layout tool that allows collaboration on designs, etc... Think Google Docs for circuit design.)
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Hello group,
Andrew sent me a couple of the antennas he mentioned, above, to play with (Thanks, Andy), which got me motivated to take my 1st dive into using a nanoVNA.
I promised Andrew I'd share results of testing the two antennas. Let me remind everyone that while I consider myself reasonably adept at electronics troubleshooting (3 or 4 'lives' in electronics maintenance), I'm not formally educated in the field nor am I a HAM operator. I hope the attached images will be viewed more as an invitation to teach me more about how to use the nanoVNA than an actual analysis of the antennas.
Starting from a knowledge level of near zero, here we go: Since Andrew is splitting the signal using one antenna to feed two SDRs that are tuned to 978MHz & 1090MHz, I set the center frequency on the VNA at the midpoint between the two freqs (1034MHz), & span to 200MHz. On the *very* slim chance that I set up the VNA correctly, It looks like the dipole has a worst case SWR of around 4.6 & the Slim Jim was basically off the chart at 1090MHz.Measurements were taken with the antennas hanging on the 6" long cable that came with the nanoVNA.
Even if I did the tests correctly, I'm not sure if the above has any real meaning for a receive-only antenna. If there's a better test that can be accomplished with the nanoVNA and someone is willing to walk me through the setup, I'll be happy to run the test(s), or I can forward the antennas to someone with more RF-foo. Shoot me a direct email if you're interested.
Charlie
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Eric Page
Joined: 15 Feb 2017
Posts: 245
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| Posted: Sun Oct 25, 2020 7:45 am Post subject: Re: ADS-B and Transponder antenna... |
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There's an RF Engineer who works for Tektronix, Alan Wolke, who has a very good YouTube channel. Among other things, he's recently been posting a series of videos on how to use the nanoVNA for various measurements.
Note that the following playlist does not list the videos in the order they were posted, but I would recommend at least watching #312 and #313 before any others.
https://www.youtube.com/playlist?list=PL4ZSD4omd_AylEyNCQYR3RcEb0olukPEJ
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andymeyer
Joined: 31 Mar 2015
Posts: 54
Location: SW MI
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| Posted: Fri Oct 30, 2020 1:15 pm Post subject: Re: ADS-B and Transponder antenna... |
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Charlie,
I saw the plots, but I don't know what I'm looking at... Am I way out on frequency, other issues? Any thoughts yet?
Andy
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Ceengland
Joined: 11 Oct 2020
Posts: 391
Location: MS
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| Posted: Fri Oct 30, 2020 2:39 pm Post subject: ADS-B and Transponder antenna... |
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On Fri, Oct 30, 2020 at 4:33 PM andymeyer <meyerkc135(at)gmail.com (meyerkc135(at)gmail.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: "andymeyer" <meyerkc135(at)gmail.com (meyerkc135(at)gmail.com)>
Charlie,
I saw the plots, but I don't know what I'm looking at... Am I way out on frequency, other issues? Any thoughts tyet?
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Unfortunately, I'm not sure what I'm seeing, either. I suspect that it has little meaning when for a receive-only antenna, as indicated in the conversation at this site:
https://ham.stackexchange.com/questions/382/what-is-the-relationship-between-swr-and-receive-performance#:~:text=Simplified%20answer%3A,between%20SWR%20and%20receive%20performance.&text=SWR%20is%20a%20measure%20of,between%20the%20transceiver%20and%20antenna.
*IF* I set up the nanoVNA correctly, the graphs indicate a worst case SWR for the dipole of around 4, where the pointer is on the right side of the screen. The J antenna SWR went 'off the chart' at minimal deviation above the center frequency I used, which was the numeric midpoint between 978MHz & 1090MHz. It should also be noted that getting my hand, or anything else, anywhere near either antenna had significant effects on the SWR. While the SWR looks awful, it probably has no real effect on the antennas' performances when used only to receive a signal, as would be the case with ADSB-in.
I'm afraid that to get any valid numbers on receive quality, we'd have to find someone that can measure the actual signal strength on the two frequencies of interest, when using these antennas.
As I said, I'll be happy to pass them on to someone else, if they can do a better job in testing them.
Sorry that I haven't been able to produce more useful data.
Charlie
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nuckolls.bob(at)aeroelect
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| Posted: Sat Oct 31, 2020 2:46 am Post subject: ADS-B and Transponder antenna... |
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At 10:45 AM 10/25/2020, you wrote:
| Quote: | --> AeroElectric-List message posted by: "Eric Page" <edpav8r(at)yahoo.com>
There's an RF Engineer who works for Tektronix, Alan Wolke, who has a very good YouTube channel. Among other things, he's recently been posting a series of videos on how to use the nanoVNA for various measurements.
Note that the following playlist does not list the videos in the order they were posted, but I would recommend at least watching #312 and #313 before any others.
https://www.youtube.com/playlist?list=PL4ZSD4omd_AylEyNCQYR3RcEb0olukPEJ |
just had a chance to review the gentleman's work . . . great find
Eric . . . thanks for the head's up!
Bob . . .
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Eric Page
Joined: 15 Feb 2017
Posts: 245
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| Posted: Sun Nov 01, 2020 4:46 pm Post subject: Re: ADS-B and Transponder antenna... |
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Here's another useful resource for learning the nanoVNA. It's a demo board that you connect to the device in order to learn what the test response should look like for various kinds of circuits.
https://preview.tinyurl.com/yxz2hast
I bought one and it seems to be well made. My only complaint is the tiny U.FL connectors they used on the board. They're a bit of a pain to mate, and they're only designed for a few dozen mating cycles, so it's not a lifetime tool. But hey, whaddya want for $13.00?!
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nuckolls.bob(at)aeroelect
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| Posted: Mon Nov 02, 2020 8:21 am Post subject: ADS-B and Transponder antenna... |
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At 06:46 PM 11/1/2020, you wrote:
| Quote: | --> AeroElectric-List message posted by: "Eric Page" <edpav8r(at)yahoo.com>
Here's another useful resource for learning the nanoVNA. It's a demo board that you connect to the device in order to learn what the test response should look like for various kinds of circuits.
https://preview.tinyurl.com/yxz2hast |
I'd seen that offered on Banggood . . . probably
ought to have one.
I do have an earlier version of the NanoVNA that
was barely used used before I acquired the VNATiny
that comes with some sophisticated PC based
management apps . . . but it's NOT self contained.
There are some apps that run in hand held Android
devices . . . I need to explore that further.
I ordered a 4", 1.5G version of the NanoVNA last
night . . . much handier for field and/or quick
look-see tasks. I just may have a very slightly
used NanoVNA for sale pretty soon!
Bob . . .
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andymeyer
Joined: 31 Mar 2015
Posts: 54
Location: SW MI
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| Posted: Tue Nov 03, 2020 10:33 am Post subject: Re: ADS-B and Transponder antenna... |
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Bob,
If you'd like a set of antenna to test and try out with the VNA, I can get a couple on their way to you - where do I send them?
Andy
| nuckolls.bob(at)aeroelect wrote: | At 06:46 PM 11/1/2020, you wrote:
| Quote: | --> AeroElectric-List message posted by: "Eric Page" <edpav8r>
Here's another useful resource for learning the nanoVNA. It's a demo board that you connect to the device in order to learn what the test response should look like for various kinds of circuits.
https://preview.tinyurl.com/yxz2hast |
I'd seen that offered on Banggood . . . probably
ought to have one.
I do have an earlier version of the NanoVNA that
was barely used used before I acquired the VNATiny
that comes with some sophisticated PC based
management apps . . . but it's NOT self contained.
There are some apps that run in hand held Android
devices . . . I need to explore that further.
I ordered a 4", 1.5G version of the NanoVNA last
night . . . much handier for field and/or quick
look-see tasks. I just may have a very slightly
used NanoVNA for sale pretty soon!
Bob . . . |
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http://www.matronics.com/Navigator?AeroElectric-List |
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