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For an amateur rocket project, I want to receive the GPS signal from 2 antennas placed in the opposite directions, but I'm very beginner in RF domain.

So my first thought is to use a signal Power Splitter and an LNA (like LaNA from NoonELEC) to re-boost the power lost from the Power splitter and feed-up a Neo8N GPS Receiver.

Am I missing something in my design? or should I consider using 2 GPS receiver each use its own antenna and then merge the 2 outputs in software.

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  • \$\begingroup\$ also note that GPS receivers must shut themselves off when they detect they travel at rocket-typical speeds or heights! \$\endgroup\$ Oct 18, 2021 at 21:55
  • \$\begingroup\$ @MarcusMüller I'm not aware of such limitation, is that a security/safety guard built-in requirement in GPS receivers? \$\endgroup\$
    – Zskdan
    Oct 18, 2021 at 22:03
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    \$\begingroup\$ at what maximum speeds and altitudes your GPS receiver works: check with the data sheet, and / or with ublox! They're really a helpful bunch. \$\endgroup\$ Oct 18, 2021 at 22:21
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    \$\begingroup\$ You CAN buy GPS receivers without the height or speed (about Mach 2) limitations; but you'll have to jump through all sorts of export paperwork hoops to get them, and probably for amateur rocketry it'll be completely impossible. \$\endgroup\$
    – user16324
    Oct 18, 2021 at 22:33
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    \$\begingroup\$ @mkeith you're right. Our rocket maximal speed will be around 980km/h (0.80 mach), we are not allowed to reach 1mach due some safety limitation imposed by local regulatory. \$\endgroup\$
    – Zskdan
    Oct 19, 2021 at 10:05

2 Answers 2

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If your GPS doesn't natively support 2 antennas (take a look a diversity antenna) than the RF project is really complicated and expensive.

Consider, as you said, 2 GPS receivers.

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    \$\begingroup\$ Unfortunately Neo8N does not support diversity antenna :-( Sure, I'll certainly go for 2 GPS receivers. But I want to have good understanding on what makes this project so complicated .. \$\endgroup\$
    – Zskdan
    Oct 18, 2021 at 22:48
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    \$\begingroup\$ @Zskdan, Re, "what makes this...so complicated?" TLDR: If you connect two antennas to each other, then you no longer have two antennas. You now have one array antenna which, if it was not purposely and carefully designed, may not do anything like what you expected it to do. \$\endgroup\$ Oct 19, 2021 at 1:47
  • \$\begingroup\$ @Zskdan If it doesn't support diversity then you are unlikely to improve anything with two antennas, but likely to make the signal worse. \$\endgroup\$
    – Lundin
    Oct 19, 2021 at 6:21
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Without RF measuring tools, or antenna experience, you might try something really simple first, to see if it meets your needs. Such a simple approach works adequately for ballooning GPS. A dead-simple antenna is shown below: simple GPS antenna


It can be constructed with magnet-wire, and has a reasonably wide bandwidth making cutting lengths not-too-critical.

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  • \$\begingroup\$ Thanks for the hint, but unfortunately this cannot work for me because the rocket core is a carbon fiber (conductive) tube with a 20cm diameter but the 1/2 wavelength of the GPS signal is ~= 10 cm. Although I'll keep this for other rocket mechanical design. \$\endgroup\$
    – Zskdan
    Oct 19, 2021 at 9:58
  • \$\begingroup\$ If the core is carbon fiber, maybe you can put a slot antenna in the wall of the core. I think some slot antennas are nearly omnidirectional. This is just a speculation. Not at all sure it will work. \$\endgroup\$
    – user57037
    Oct 20, 2021 at 2:00

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