[HN Gopher] Broadcasting LoRa packets wihout a radio [video]
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       Broadcasting LoRa packets wihout a radio [video]
        
       Author : koutsie
       Score  : 66 points
       Date   : 2024-03-25 23:27 UTC (23 hours ago)
        
 (HTM) web link (www.youtube.com)
 (TXT) w3m dump (www.youtube.com)
        
       | ysleepy wrote:
       | wow, that is a great hack
        
       | saidinesh5 wrote:
       | I really liked the explanation of how he used harmonics to get to
       | the frequency he desired.
       | 
       | Also, LoRa is _really_ good when it comes to low power data
       | transmission. To share a recent example, with just ~100mW of
       | transmission power, they managed to fly an RC plane to a distance
       | of 100km: https://www.youtube.com/watch?v=CYJ2UOrlXgM .(Their
       | transmitter from the ground station was configured at a higher
       | power, but the transmitter on the aircraft was transmitting
       | telemetry back at 100mW throughout the distance)
       | 
       | Another related fun project is using raspberry pi gpio to work as
       | an FM transmitter: https://github.com/markondej/fm_transmitter
        
         | thijson wrote:
         | I looked a bit into the LORA protocol. It does offer reception
         | below the noise floor. LORA doesn't do anything to attempt to
         | make other LORA transmissions seem like noise to a receiver
         | that's attempting to lock to your transmission. This makes it
         | possible for a transmission that's closer to the receiver to
         | essentially jam a transmission that's far from it. I guess
         | since LORA isn't used that much, it's not a problem these days.
         | I think it's being used as part of Amazon's sidewalk network
         | though.
        
         | FrankPetrilli wrote:
         | Notably, Wez's flight was done with 2.4GHz LoRa (this was one
         | of his main points, to address naysayers who claimed a 2.4GHz
         | link could never achieve >100km) while Charles is using 900MHz
         | - the same setup that achieved 100km (100mW with a lightly
         | directional antenna on one end, ExpressLRS 50Hz RF mode) would
         | have a theoretical range of >500km on 900MHz. LoRa at longer
         | wavelengths can achieve some incredible feats - like microwatts
         | or nanowatts of power to >1 mile as we saw here. :)
        
         | ranger_danger wrote:
         | 100km @ 100mW is not impressive when it's attached to a 30dBi
         | antenna...
        
         | topspin wrote:
         | Doesn't LoRa have a pretty constrained duty cycle? I read the
         | regs on LoRa (for the US at least) and found that you're
         | required to limit transmission frequency to 1% (36s/h). I'm
         | guessing you'd have to go well past that to operate an RC
         | aircraft in the conventional manner. If you're just commanding
         | waypoints I suppose you could be compliant.
        
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       (page generated 2024-03-26 23:00 UTC)