Interested in cheap GPS trackers?

Discussion in 'Rocketry Electronics and Software' started by Eric Jimenez, Feb 28, 2019.

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  1. Mar 19, 2019 #31

    midpower_madness

    midpower_madness

    midpower_madness

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    Yes, 1- 5 data cycles per second from the Ublox NEO M8N is being transmitted at full power from the LoRa device. Spreading factor on these EByte modules is huge!

    Note:

    On a model rocket we Canadians don't have wavers and the ceiling is unlimited to anything 160 Ns of total installed impulse or less. ie. You can launch anytime - anywhere with CTI 159G125 without permission. It is a model rocket motor. High power is far more of a challenge, however for H class and above.


    Posted the Canadian standards below:

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    This Radio Standards Specification (RSS) sets out requirements for the certification of radio equipment for the location and monitoring service (LMS) in the band 902-928 MHz.
    ------------------------------
    6.2 Types of Modulation
    The devices may employ any type of modulation technique. The type of modulation used must be reported.

    6.3 Frequency Stability
    The carrier frequency shall not depart from the reference frequency in excess of ±2.5 ppm for any type of equipment unless indicated otherwise.

    Fixed N-LMS transmitters with an emission bandwidth located more than 40 kHz from the band edge, intermittently operated hand-held readers and mobile transponders are exempt from meeting the frequency stability limit.

    6.4 Transmitter Output Power
    The output power shall be within ±1.0 dB of the manufacturer's rated value, and the e.r.p. shall not exceed 30 watts for the band 902-927.25 MHz and 300 watts for the band 927.25-928 MHz.

    6.5 Transmitter Unwanted Emissions
    The LMS sub-band edges for multilateral LMS systems for which unwanted emissions shall be attenuated are specified in section 6.1.1.

    6.5.1 Emission Mask A – Wideband Multilateral Transmitters
    Except as provided in section 6.5.4, the unwanted emission limits for wideband multilateral transmitters operating in the sub-bands 904-909.75 MHz, 919.75-921.75 MHz, and 921.75-927.25 MHz shall comply with the following:

    In any 100 kHz band outside the equipment operating sub-band edge, the power of emissions shall be attenuated below the maximum permitted transmitter output power, Pmax, by the following equation:

    16 + 0.4(fd - 50) + 10 log10 B dB, or 31 dB, whichever is more stringent (attenuation greater than 66 dB is not required).

    Where:

    - B is the occupied bandwidth in MHz; and
    - fd is the magnitude of the difference between the centre frequency of the measurement bandwidth and the centre frequency of the equipment operating sub-band, expressed as a percentage of the occupied bandwidth.

    6.5.2 Emission Mask B – Narrowband Multilateral Forward Link Transmitters
    For narrowband multilateral forward link transmitters operating in the band 927.25-928 MHz, the power of any emission outside the equipment operating sub-band edge shall be attenuated below the maximum permitted transmitter output power, Pmax , by at least:

    116 log10 ((fed+10)/6.1) dB or 50 + 10 log10 Pmax dB, or 70 dB, whichever is less stringent.

    Where:

    - fed is the magnitude of the difference between the centre frequency of the measurement bandwidth and the equipment operating sub-band edge, expressed as a percentage of the occupied bandwidth.

    6.5.3 Emission Mask C – Other Transmitters
    Except as provided in sections 6.5.1, 6.5.2 and 6.5.4, the unwanted emission of all other transmitters operating in the band 902-928 MHz shall comply with the following:

    The power of any emission outside the equipment operating sub-band edge shall be attenuated below the maximum permitted output power Pmax by at least 55 + 10 log10 Pmax dB.

    6.5.4 Emission Mask D – Intermittent Transmitters
    In the band 902-928 MHz, mobile transponders with integral antennas (i.e. transmitters that respond only to a received radio signal) and intermittently operated hand-held transmitters shall not be required to comply with the above emission masks, provided that their 20 dB bandwidth does not exceed the maximum occupied bandwidth permitted. In addition, on any frequency distanced from the carrier frequency by more than 250% of the occupied bandwidth, the power of any emission shall be attenuated below the maximum permitted transmitter output power, Pmax, by at least 43 + 10 log10Pmax dB, measured in a bandwidth of 100 kHz.

    6.6 Receiver Spurious Emissions
    Receiver spurious emissions shall comply with the limits specified in RSS-Gen.
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    Donnie likes this.
  2. Mar 19, 2019 #32

    BLH

    BLH

    BLH

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    Sounds like fun!! If radio is not frequency hopping, that would certainly be an illegal transmitter here in the US. I know of a few GPS trackers that just take the TX pin from the GPS module and connect it to the radio without frequency hopping which makes a non-compliant system...
     
  3. Apr 20, 2019 #33

    Eric Jimenez

    Eric Jimenez

    Eric Jimenez

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    After considering my options, I have decided that I would instead, make a build thread for my GPS trackers once its nearly finalized. I just received all the parts I need for them so I will start on it once my semester ends. The only parts I may plan to sell are the 3D printed enclosure/mount for it (if you have a 3D printer I will have the files on Thingiverse).
     
  4. Apr 21, 2019 #34

    ksaves2

    ksaves2

    ksaves2

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    Is this 3DR based? I experimented with it on the ground for awhile but the 2 way link (which is unneeded) was a sticking point plus I was trying to reprogram the GPS so I could put my Ham radio callsign into one of the strings so I would be absolutely legal irregardless. I bought some of the so called 500mW radios but you know that's "Chinese mW" and they are notoriously over optimistic.
    The cheap $9.95 GPS chipsets I found I was unable to program (or couldn't figure them out) and I didn't get to the point to where I could have one way communication from the tracker to the receiver. I was shooting for a $50.00 system complete basically so if I lost the rocket or it core sampled, it would
    be a lot easier to cope with the loss of a $30.00 GPS tracker. Yes GPS tracked rockets do go AWOL sometimes and if a deployment failure occurs, the electronics might not be able to take the hit. Kurt
     
  5. Apr 21, 2019 #35

    Eric Jimenez

    Eric Jimenez

    Eric Jimenez

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    It's arduino based. So far I have the system just under $35 and as small as I could get it (2.5 inch x .9 x 1.14 inch on the rocket side) without antenna.
     

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