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The idea was to send GPS data from the rocket to the ground station at 433 MHz using a Lo Ra transmitter - mainly to help locate it once it lands and also to provide in-flight telemetry.

I have a similar transceiver on the ground - but lack an appropriate antenna design. I have had it suggested that a Circular Polarised Antenna for the mobile ground station would beneficial, but I have no idea of what form this would take - either to buy or construct one from scratch.

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  • $\begingroup$ Hello David, and welcome to ham.stackexchange.com! $\endgroup$
    – rclocher3 ♦
    Jan 23 '21 at 22:03
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    $\begingroup$ Perhaps things have changed, but when my brother was flying payloads in small rockets, GPS was useless (at least in flight) because the rocket was moving too fast to get a lock. I suppose it could be helpful on land, but you'd have to be within line-of-sight to receive the telemetry. And if you're that close, you could also use standard fox-hunting direction finding techniques. $\endgroup$
    – Duston
    Jan 25 '21 at 15:39
  • $\begingroup$ I was actually hoping to use it for static location once it landed. I know that most GPS units actually cut out above a certain speed to prevent them being used in weapons. The design for the rockets are limited in terms of their altitude and thus speed by other factors so there is a slim possibility that it may track it (at least initially and finally once the parachute deploys). If I latch the last known position at will at least help. Never heard of fox-hunting DF techniques - any links $\endgroup$
    – David Allan
    Jan 26 '21 at 18:18
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You could, very quickly and cheaply, experiment with a turnstile antenna. Alternatively, checkout a QFH antenna which are also inexpensive to make, but require a little more skill.

And there are plenty of other designs as well that you'll find with very little googling!

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  • $\begingroup$ Thanks for that - Do you know of any calculators related to turnstile antennas. There appears to be some form of compensated lengths involved in the antenna design for the radiating elements and the quadrature phase shift. How is this is affected by different factors and what factors? $\endgroup$
    – David Allan
    Jan 25 '21 at 13:00

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