I have a GPS tracking device which was designed for inventory management, currently I'm using a GSM module to transmit the telemetry data (latitude and longitude only) to the base station. The problem in using GSM is it is not suitable to work in remote locations.

Is it possible to use a QRP transmitter to send the same data to the base station?

Edit: The current system is capable of sending the whole NMEA data with an interval of 1 minute, but I want only the latitude and longitude. Geographically, my locality (Kerala) is roughly divided into three climatically distinct regions. These include the eastern highlands (rugged and cool mountainous terrain), the central midlands (rolling hills), and the western lowlands (coastal plains).
Since this is a hand held portable device and supposed to operate in remote areas, there may be obstacles in between the transmitter and receiver so Line of sight communication may not be possible.

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    $\begingroup$ There is not enough information to give an accurate response. In order to reply can you elaborate on how much data you need to transfer and how often. A large amount of data or a frequently updated data set will need a higher bandwidth and therefore a higher frequency. What is the Terrain like? Line of sight? This will indicate whether or not higher frequencies can be used. How about the range? $\endgroup$
    – AndyW
    May 1 '19 at 11:32
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    $\begingroup$ Also notice that this doesn't sound like an amateur radio application at all. So, if this is for commercial purposes (or even just any application that doesn't fit your amateur radio operator license): you can use techniques like these used in QRP operations (though you'd certainly not use the 80 year old modes many QRP operators use), but you can't do that without buying a commercial license to a bandwidth of spectrum. $\endgroup$ May 1 '19 at 11:42
  • $\begingroup$ (@AndyW re: line of sight: of course, depending on data rate, we have data to show that you can reliably communicate using 2.4 GHz and no line of sight at all across most of a 300,000 people city.) $\endgroup$ May 1 '19 at 11:44
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    $\begingroup$ We also need to know what country the OP is in to be able to answer. $\endgroup$
    – Duston
    May 1 '19 at 14:06
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    $\begingroup$ Search the net for the WSPR balloons. These are very-low-power solar balloons that circle the globe, transmitting their GPS position using WSPR with a few mW. $\endgroup$
    – tomnexus
    May 8 '19 at 13:46

When you ask if a QRP transmitter could be used to solve your problem, I presume that you mean a low-powered transmitter on HF, meaning roughly 3 – 30 MHz. That would solve the problem of limited range associated with the VHF and higher-frequency bands, but a large antenna would be necessary.

The problem is that radio spectrum, especially in the HF bands, is very scarce. Because there are so many uses for scarce bandwidth, governments require licenses to use the bandwidth, and often charge large fees for the privilege. On the HF and lower-frequency bands, governments generally reserve most of the bandwidth for themselves. The only reason that there is an allocation for amateur radio is that hams were there at the very beginning of radio, and have loudly campaigned for a share ever since. Unfortunately for you, the amateur radio bands aren't available for business uses such as the one you describe.

I don't know of a frequency allocation for low-powered HF automated data transmission for business purposes, but if there were such an allocation, then licenses would surely be very expensive because the available bandwidth is so narrow. Think how much mobile phone companies are willing to pay for allocations at much higher frequencies where there is much more bandwidth available.

This fundamental problem of limited bandwidth has driven ingenious solutions to similar problems:

  • The global cellular network
  • The Iridium satellite network
  • The SNOTEL network in the Western US

If you could find another solution that would be inexpensive enough for inventory tracking and would work with handheld devices in remote locations, then fame and fortune would surely find you.

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    $\begingroup$ Excellent! I would add If you could find another solution ... then please share it here with all of us! :-) $\endgroup$
    – Mike Waters
    May 1 '19 at 19:37
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    $\begingroup$ @Sumithran I see your edit that you just want to transmit GPS coordinates, but my answer still applies. Even if you only want to transmit for one second once a week, you would still need to use scarce bandwidth. $\endgroup$
    – rclocher3
    May 1 '19 at 21:06
  • $\begingroup$ In the U.S., there is an HF ISM band at 13.56 MHz, possibly usable for ISM telemetry. Another possibility might be voice synthesis of telemetry data over CB channels (11M HF). Check the legal use cases in your RF jurisdiction. $\endgroup$
    – hotpaw2
    May 3 '19 at 18:12

If you are just transmitting GPS coordinates and at a slow rate and need a bandwidth of about 50kbps or less then have a look at LoRa technology. It is low power, low data rate and spread spectrum but it is very reliable with a range over 10km (some as far as 50km) on licence free VHF and UHF bands. It is designed for IoT uses in a noisy environment it could be the solution to your problem depending on your exact requirements.

some details below:



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