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I am working on my senior capstone and I am needing a way to send commands with as low latency as possible. I have found the LoRa but I am concerned there will be a high delay. I fly high altitude balloons and my senior project is a payload and I need a way to communicate with the Pi on the payload from the ground station(my laptop). I will be controlling a mount in as close to real time as possible. If anyone has any insight on this I would greatly appreciate your help. Thanks!

Edit: Would prefer the delay being now more than a second to two seconds max. I have funding but would prefer it not to be anything too outrageous.

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  • Define "Low Latency" and "Real Time" in units of time, you also fail to specify expected throughput in bits. It may mean the difference between a $50 off the shelf solution or a million dollar project. Your physical best case limit here is about 300 uS round trip plus processing delay, which should be good enough for a control scheme (Position Update ~1-2KHz), but if you are relying on tighter coupling then you need to rethink control algorithms and offload more work locally to the PI.
    – crasic
    Commented Oct 11, 2017 at 20:08
  • Please edit details into the question instead of posting them as comments, and take the tour to understand better how the site works in general.
    – goldilocks
    Commented Oct 11, 2017 at 20:24
  • Alright, I updated the original post with more information. Thank you. Commented Oct 11, 2017 at 20:30
  • Since Andreas Speiss broke a record 212km distance, the current world record for LoRa is now 702km. Might be worth a try... If you have a clear sight, latency should not be a problem.
    – user29510
    Commented Oct 12, 2017 at 9:24

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Use a small >5W handheld transceiver with VOX set to a decent sensitivity. VHF has a bit better range than UHF. Trip the VOX with a generic click.wav, then send your data. It’s important to use a nice USB soundadapter for this - you can get >=57600 baud with amodem and LOS. If you need to send data to the Pi, the transceiver will accomodate this. You may want to look at drone antennas instead of generic whip antennas for the band you use. If you use a whip or ducky, is important to have the same polarity on both your antennas.

You’ll need 3 3.5mm and 1 2.5mm male jacks. Remember to connect the shield properly on both ends, or there will be no love.

Romanz’ amodem package handles this well, though you will need to hack bits out of it to suit your design.

https://github.com/romanz/amodem

It is worth mentioning I can open repeaters more than 25km away with a 4W transceiver, and no LOS.

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