{"id":2501,"date":"2021-12-28T18:27:35","date_gmt":"2021-12-28T18:27:35","guid":{"rendered":"http:\/\/www.blog.exrockets.com\/blog\/?p=2501"},"modified":"2022-09-20T19:05:54","modified_gmt":"2022-09-20T19:05:54","slug":"100-mw-433-mhz-long-range-30-km-gps-tracker-kit","status":"publish","type":"post","link":"http:\/\/www.blog.exrockets.com\/blog\/100-mw-433-mhz-long-range-30-km-gps-tracker-kit\/","title":{"rendered":"100 mW 433 MHz LoRa 30+ km GPS tracker kit"},"content":{"rendered":"

\"\"<\/a><\/p>\n

After I made the GSM-GPS tracker, I\u2019ve realized that the cell coverage is usually not available at sites where rockets are being launched. For a while I\u2019ve been thinking of making an independent from the cellular network tracker for rockets, planes etc. With the LoRa SX1278 chips this became an easy task.<\/p>\n

TRANSMITTER<\/strong><\/p>\n

\"\"<\/a><\/p>\n

Transmitter part is straight forward following the recommended hardware design by Semtech. For better results I am using an inexpensive 32 MHz TCXO instead of a Crystal. 26 MHz clock source works too, however you will need to re-calculate the frequency register settings accordingly. Because the GPS altitude estimation is relatively inaccurate, for altitude measurement I\u2019ve installed a barometric pressure sensor BMP280. There is also a built in LiPo charging circuit powered from the USB port.<\/p>\n

RECEIVER<\/strong><\/p>\n

\"\"<\/a><\/p>\n

This receiver is also following the recommended hardware design by Semtech. For better results I am using an inexpensive 32 MHz TCXO (+-1ppm) \u00a0instead of a Crystal. Similar to the transmitter there is also a built in LiPo charging circuit powered from the USB port. In addition to that this receiver has a128x64 OLED display, memory to record data for about an hour and some buttons for screen control. There is also a 10dB\u00a0 LNA (BGA427) to boost the signal and increase the link distance.\u00a0 Both parts TX and RX are powered by a 3.7 LiPo battery.<\/p>\n

PCB DESIGN AND ACTUAL DEVICE<\/strong><\/p>\n

\"\" <\/a>\"\" <\/a>\"\"<\/a><\/p>\n

LoRa SX1278<\/strong><\/p>\n

Semtech SX1278 is a transceiver chip using LoRa modulation. You can find more information about the LoRa modulation technique here<\/a>. Now I am going briefly to explain my findings when I was working with this chip.<\/p>\n

Power – The SX1278 has a maximum output power of 100mW but you have to make sure the battery can supply about 150-160 mA peak current, otherwise the chip might reset.<\/p>\n

Frequency \u2013 this chip support different frequency bands from 137MHz to 525MHz but I have chosen the 433MHz band since it is not licensed and it is a good compromise between antenna size and RF signal propagation.<\/p>\n

SF \u2013 The higher the Spreading Factor, the less susceptible is the link to noise and interference and the higher is the reception range. However higher Spreading Factor also means longer transmission time.<\/p>\n

SX1278 can support SF12 but I was unable to establish reliable link with this Spreading Factor. I\u2019ve asked on Semtech\u2019s boards but got no response so far. On other hand link established with SF11 proved to be very stable.<\/p>\n

BW \u2013 Channel Bandwidth is important parameter since it affects the RF link in opposite way to the Spreading Factor. Higher Bandwidth means the link is more susceptible to noise and interference, reception range is lower and transmission time is shorter.<\/p>\n

This transceiver can support Bandwidths from 7.8kHz to 500kHz. In my test 62.5kHz is the lower limit for Crystals and 15.6 is the lower limit for TCXO (+-1ppm) for establishing a reliable link.<\/p>\n

EC \u2013 Error correction code \u2013 this will increase the packet size by adding additional bits for error correction but it will also increase the reception range. Of course EC 4 works best but it practically doubles the packet length.<\/p>\n

Clock source \u2013 TCXO or Crystal? According the datasheet the LoRa modulation allows for +-49% variation in the clock source from the center frequency and still the chip being able to decode the packet. Having a more stable clock of course allows for lower Bandwidths and higher Spreading Factors. I\u2019ve done a simple test to see the temperature drift in a crystal compared to a TCXO. Here\u2019s a chart of both running for some time and how the frequency deviates during this time.<\/p>\n

\"\"<\/a><\/p>\n

ANTENAE<\/strong><\/p>\n

\"\"<\/a><\/p>\n

 <\/p>\n

Transmitter antenna is a simple 433 MHz whip antenna from Aliexpress with +1.5 dBm gain.<\/p>\n

 <\/p>\n

\"\"<\/a><\/p>\n

 <\/p>\n

And for the receiver I tested a foldable whip antenna again from Aliexpress and a DIY 433 MHz Yagi antenna.<\/p>\n

 <\/p>\n

 <\/p>\n

The Yagi antenna has 4-elements with +10 dBm signal gain and was constructed from aluminum flat ribbons. All calculations were done using VK5DJ\u2019 Yagi Calculator<\/a>\u00a0 including the required BALUN made from piece of coax cable.<\/p>\n

TESTING<\/strong><\/p>\n

First thing to do before testing was to find noise free spot on the 433 MHz band with sufficient bandwidth for my tracker. You don\u2019t actually need to do this, but for best range and performance it\u2019s always advisable to select frequency which is not occupied by other devices.\u00a0 \u00a0For that purpose I used an inexpensive USB SDR stick and AIRSPY SDR Studio. If you don\u2019t have a SDR USB stick, don\u2019t worry \u2013 I\u2019ve built in a function in the receiver that can help you to find the free frequencies, but this will be explained later in the software part.\"\"<\/a>Once I determined that the 433.1200 MHz was free of other transmitters, I set up the transmitter and receiver to the same center frequency using the PC host program for the tracker kit (details for that later). Also I set the bandwidth to 20.8 kHz for both.\"\"<\/a>First test was to see the range within line of sight. For that I placed the transmitter on the roof at about 30m above ground and drove away for few kilometers. Checked the signal and it was strong. Then I drove further away \u2013 at about 28km distance I reached the hills where the signal disappeared using the whip antenna. Then I switched to the Yagi antenna and the signal was still strong. At about 30km I was on the top of the hills and signal reception was still strong. As soon as I went behind the hills and no longer in line of sight the signal disappeared. So the reception range in line of sight is definitely more than 30km but there is no suitable place near me for testing.\"\"<\/a>Second test was with transmitter placed on the ground hidden in the bushes:\"\"<\/a>It was sunny day and I could see far away the field where I was testing the tracking kit. You can get an idea of what kind of terrain I used for the test.\"\"<\/a>The finishing point was far back, you can barely see the hills on the background.\"\"<\/a>Test results were far better than I would have expected. The field as you can see has some ravines and since the transmitter was on the ground the reception really depended on where I was at the moment. But simply lifting the receiver above my head was sufficient to improve the reception significantly.<\/p>\n

\"\"<\/a>This table summarizes the reception range measurements. As you can see from the table above in point 5 at about 15km from the transmitter I had to use the Yagi antenna because I was in a ravine where I lost the signal with the whip antenna. However switching to the Yagi increased the signal strength significantly. Once I was out of the ravine I switched back to the whip antenna. At the 18th<\/sup> kilometer (P6) I reached the hills still receiving signal with the whip antenna. When I started climbing the hill the signal got stronger but it was no longer within the purpose of this test.<\/p>\n

As a conclusion when the rocket\/plane is in the air in line of sight, the reception range is at least 30km. Once the model rocket\/plane is on the ground strongly depends on the terrain lay and vegetation with range up to 18-20 km on the open field. However in the worst case scenario tests I\u2019ve recorded range reduction down to 5-6 km in woody hills but this rarely can be the terrain where we launch rockets and model planes. Nevertheless using a grid search of 5-10 km per grid depending on terrain will allow you to cover very large area with this tracker.<\/p>\n

FIRMWARE<\/strong><\/p>\n

After developing an USB bootloader, I\u2019ve made a PC firmware flashing tool which comes in handy when new firmware has to be uploaded in the devices. The Bootloader is fully protected inside the Microcontroller and can\u2019t be re-written and\/or erased. So even if the flashing process is suddenly interrupted for example by a power failure, the device can be re-flashed which makes it virtually impossible to \u201cbrick\u201d the LoRa GPS tracking kit with firmware updates. Firmware updates became very straightforward and easy to execute by users.\"\"<\/a>FIRMWARE UPDATE PROCEDURE:<\/p>\n

1. Connect the device (either transmitter or receiver) to the PC with the USB cable
\n2. Start the GPS LoRa TRACKING \u2013 FLASH TOOL
\n3. Turn on the device
\n4. Wait until the red indicator (#1) turns green and says \u201cUSB CONNECTED\u201d
\n5. Wait until the program indicates \u201cDEVICE RECOGNISED)
\n6. Click on button FILE (#2) and select the firmware file (latest files are included in folder DATA FILES)
\n7. Wait until data is loaded (a lot of strange digits and letter will appear)
\n8. Click on button \u201cFLASH\u201d (#3) and confirm that you wish to continue
\n9. Wait until firmware flashing has finished
\n10. Restart the device by switching it off and back on
\n11. That\u2019s it flashing is done<\/p>\n

Again – don\u2019t worry you can\u2019t \u201cbrick\u201d and render it inoperable \u2013the Bootloader is protected and if something goes wrong, all you need to do is to re-flash the firmware.<\/p>\n

The firmware and the Bootloader were written in POSITRON BASIC<\/a>\u00a0 compiler for PIC Microcontrollers \u2013 excellent inexpensive compiler, written by Les Johnson, with lots of libraries, tools and very friendly and supportive community. Many professional and commercial products operate with firmware written in this language, definitely worth taking a look if you are interested in PIC Microcontrollers.<\/p>\n

\u00a0<\/strong>SOFTWARE<\/strong><\/p>\n

\"\"<\/a>For easy set-up and improved functionality I\u2019ve written a small PC application. Some of the buttons and functions are available for both, receiver and transmitter and some specific for each device.<\/p>\n

First you start the application, then connect the USB cable and start the device. After 5-6 seconds the device will be recognized and the red rectangle in the top left corner will turn green, saying \u201cUSB CONNECTED\u201d.<\/p>\n

Note: The very first time the device is connected to a PC it might take a bit longer to install all drivers and the time allowed for USB connection will expire at which point you simply have to restart the device by switching it off and back on.<\/p>\n

Once the device is connected and recognized, the program will display the current settings and firmware revision, as well some buttons will become available depending on whether transmitter or receiver has been plugged in.<\/p>\n

FUNCTIONALITY<\/p>\n

Settings:<\/p>\n

1. CYCLE (TX) \u2013 the time in seconds between transmissions, 0 means constant transmission, it is not advisable since constant RF noise deteriorates the GPS accuracy
\n2. FREQUENCY (TX and RX) \u2013 a code, representing the center frequency \u2013 should be the same for TX and RX. The actual frequency is displayed in the upper right corner where it says Frq:000.0000 MHz
\n3. BW (TX and RX) \u2013 the channel bandwidth, should be the same for TX and RX. Higher Bandwidth means the link is more susceptible to noise and interference, reception range is lower and transmission time is shorter. Bandwidth of 20.8kHz is best suited for long range and stability
\n4. POWER (TX) \u2013 transmitter power \u2013 0 means minimum power and 15 means maximum power. Higher power means longer link range but shorter battery life
\n5. ZONE (TX) \u2013 time zone in which the device is being used. Because the GPS only outputs the UTC time, for easy clock synchronization you can adjust the time. Does not affect the link in any way.
\n6. BATTERY (TX) \u2013 minimum battery voltage for transmission. If the battery falls below this voltage, the transmitter will not send packets. This is to prevent full battery discharge and potential damage<\/p>\n

System Information:<\/p>\n

1. Frq: – current frequency calculated from the frequency code
\n2. Fw: – firmware revision
\n3. Bl: – bootloader revision<\/p>\n

Buttons:<\/p>\n

1. CLEAR \u2013 will reset the form
\n2. DL BANKx \u2013 use this to download tracking information, recorded in the receiver\u2019s memory
\n3. READ \u2013 read the device\u2019s current settings
\n4. WRITE \u2013 apply the current settings to the device. The device will reboot after that
\n5. SET RX\/TX \u2013 reserved for future use with an aerial packet repeater
\n6. RSSI \u2013 use this to scan the RF spectrum few MHz above and below the current center frequency. It can be used to find which frequencies are occupied and which are free and respectively set the tracking kit to the least noisy frequency
\n7. TRACK \u2013 although the receiver is standalone device, you can connect it to the PC\/Laptop and receive the information on your screen. *Note \u2013 I was planning to add direct link with Google Earth so the tracking can be displayed directly in Google Earth<\/p>\n

PC tracking:<\/p>\n

1. RSSI: – packet\u2019s signal strength. Lower values indicate lower signal strength, note the value is negative
\n2. SNR: – signal-to-Noise strength, higher values mean better signal quality and lower in-band noise
\n3. Fn: – nominal frequency. This the frequency at which the transmitter was preset
\n4. Fa: – actual frequency. Due to temperature variation, acceleration load, crystal aging, the actual frequency of the used crystal\/TCXO changes. This value represents the relative frequency difference between the transmitter and the receiver. The closer these values he better. With higher relative difference between both TX and RX, lower channel bandwidths will become unstable
\n5. LAT: – GPS latitude
\n6. LON: – GPS longitude
\n7. ALT: – this is relative barometric altitude above start. Since the vertical positioning with GPS is very inaccurate, I am using barometric sensor to determine the relative vertical position with respect the altitude where the TX was switched on
\n8. DIS: – Distance and heading to the current position as seen from the starting point. At each new packet the receiver calculates the distance and the heading to the current position as seen from the starting point based on the GPS coordinates. Note this is only with respect to the initial starting point, so if you move around with the receiver, the distance won\u2019t account for your movement and still the distance and the heading will be with respect the initial starting point
\n9. BAT: – transmitter\u2019s battery voltage
\n10. POS: – each packet sent from the transmitter has an embedded serial number which is compared to the total number of received packets by the receiver. Left number represents the number of received packets, and the right is the packet\u2019s serial number. Comparing both numbers you can see if and how many packets have been dropped
\n11. TLO: – local time based on the PC clock
\n12. TPA: – packet time stamp. Each received packet has an embedded time stamp based on the GPS clock<\/p>\n

Assuming that all settings have already been done via the PC software and the Transmitter and the Receiver have been set-up with the same center frequency and bandwidth, it is time to put the LoRa GPS tracking kit in use.<\/p>\n

\u00a0<\/strong>TRANSMITTER GUID<\/strong><\/p>\n

– after the TX is switched on, it will remain silent for about 5 seconds while loading internal information
\n– then for about 6 seconds the status LED will start blinking very fast indicating that the TX is waiting to connect to the USB
\n– when the TX sees no USB connection, it switches to normal operation
\n– Immediately after that the TX sends one packet with all zeroes, except the battery voltage, to confirm that it is alive
\n– next the TX stays silent regardless of the transmission cycle time set through the PC software until the GPS finds valid signal fix and the GPS LED starts blinking with 1s period
\n– after the GPS fix has been found, the TX waits for about 20 valid position fixes to roll from the GPS
\n– after 20 valid fixes, the TX averages several GPS position coordinates and sends the second packet, which now holds all coordinates. Coordinates from this packet are used from no on as the starting point for calculating the distance and the heading for each new packet
\n– from now the TX continue transmitting packets with the preset period even if for some reason no signal is available for the GPS so you can track it using Fox hunting techniques (later more explanation for that)<\/p>\n

Note: if the battery voltage drops below the predetermined level, the transmitter will stop sending packets to prevent further battery discharge.<\/p>\n

RECEIVER GUIDE<\/strong><\/p>\n

After the TX is switched on, it will remain silent for about 5 seconds while loading internal information. Next screen shows receiver\u2019s battery voltage \u2013 wait to continue\u00a0\u00a0\"\"<\/a>Next screen is a welcome screen showing system information \u2013 wait to continue\"\"<\/a>Next screen will check if the USB cable is connected \u2013 wait to continue\"\"<\/a>USB connection has not been detected \u2013 wait to continue\"\"<\/a>This screen explains buttons meaning. DOWN\/UP means either decrease\/increase or move down and up. REC means either set or continue, STOP is usually resetting the current process. Press REC (Next) to continue\"\"<\/a> Next screen asks for the frequency mode, for now only NORMAL is available, the rest is reserved for future use. Press DOWN to select NORMAL mode\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 \u00a0 \"\"<\/a>Next screen displays the current frequency set in the memory. You can adjust it by pressing DOWN\/UP. If no changes are required or the frequency has been set, press REC to set and continue. Pressing STOP will reset the device. Any changes made here remain only for the duration of this session, the preset frequency in the memory is not being changed\"\"<\/a>Next screen displays the current bandwidth set in the memory. You can adjust it by pressing DOWN\/UP. If no changes are required or the bandwidth has been set, press REC to set and continue. Pressing STOP will reset the device. Any changes made here remain only for the duration of this session, the preset bandwidth in the memory is not being changed\"\"<\/a>Next few screens will display the currently selected frequency and bandwidth for few seconds \u2013 wait to continue<\/p>\n

Then we arrive at the main menu. Press DOWN to go in RECEIVER mode, UP to erase memory, REC to view memory, STOP for fox hunt.\"\"<\/a>RECEIVER (TRACKING MODE):<\/p>\n

This is the main working mode where data is being received from the transmitter and visualized on the screen. The meaning of the fields is the same as in the PC application.\"\"<\/a>1. RSSI: – packet\u2019s signal strength. Lower values indicate lower signal strength, note the value is negative
\n2. SNR: – signal-to-Noise strength, higher values mean better signal quality and lower in-band noise
\n3. N: – indicates that currently tracking data is not being recorded in the memory
\n4. LAT: – GPS latitude
\n5. LON: – GPS longitude
\n6. ALT: – this is relative barometric altitude above start. Since the vertical positioning with GPS is very inaccurate, I am using barometric sensor to determine the relative vertical position with respect the altitude where the TX was switched on
\n7. DIS: – Distance and heading to the current position as seen from the starting point. At each new packet the receiver calculates the distance and the heading to the current position as seen from the starting point based on the GPS coordinates. Note this is only with respect to the initial starting point, so if you move around with the receiver, the distance won\u2019t account for your movement and still the distance and the heading will be with respect the initial starting point
\n8. 00:00:00: – packet time stamp. Each received packet has an embedded time stamp based on the GPS clock
\n9. 0.00 V: – transmitter\u2019s battery voltage
\n10. POS: – each packet sent from the transmitter has an embedded serial number which is compared to the total number of received packets by the receiver. Left number represents the number of received packets, and the right is the packet\u2019s serial number. Comparing both numbers you can see if and how many packets have been dropped<\/p>\n

\"\"<\/a>During tracking mode you can start recording the received packets in the memory. For this press REC button and it will show the following screen:<\/p>\n

Using the UP and DOWN button select a memory bank where you want data to be recorded. F\/E – F means the bank has some data written in it or E is for \"\"<\/a>empty, thus there is no data in the selected memory bank. Once you have selected a memory bank, you can start recording data by pressing REC button, or if you press the STOP button you can stop recording the tracking data (if it was currently recording). Pressing any of the both buttons REC or STOP will return you to the previous screen with the tracking data. If data is being recorded in the memory, instead of N in the upper right corner a R will appear.<\/p>\n

 <\/p>\n

ERASE MEM:<\/p>\n

\"\"<\/a>This menu allows you to format all memory banks.<\/p>\n

Just follow the instructions \u2013 you will be asked to confirm few times that you are sure, buttons for confirmation change on each screen where you are asked to confirm. This is done in order to prevent accidental deletion.\u00a0 Pressing any other button than the confirmation button will restart the device.<\/p>\n

When you have browsed through all confirmation screens, an erasure counter will appear. Once the memory erasure has finished the devise will reboot.<\/p>\n

 <\/p>\n

VIEW MEM:<\/p>\n

\"\"<\/a>This menu will visualize the currently recorded data in the memory banks.<\/p>\n

 <\/p>\n

\"\"<\/a>If you press UP for yes, the next screen will appear. DOWN for no will restart the device and bring you back to the beginning.<\/p>\n

Use the UP and DOWN buttons to select which data bank should be displayed. Once you have selected the desired memory bank, press REC to display the data or STOP to exit and reboot the device.<\/p>\n

\"\"<\/a>Displaying the memory will bring forward the same screen as in tracking mode.<\/p>\n

Use the UP and DOWN buttons to browse through the different packets. If you wish to return to the main screen, press STOP to restart the device.<\/p>\n

 <\/p>\n

FOX HUNT:<\/p>\n

This mode is used whenever the GPS is unable to output valid position fix and the transmitter is sending 0-filled packets or if the transmitter is close enough and outputting positional data but the accuracy is low and we will use the signal strength of each packet to find the transmitter. More on Radio Fox Hunting<\/a><\/p>\n

For this purpose best is if you are using a directional (Yagi) antenna but an omnidirectional whip antenna can be used too with good results. The main idea is that you hold the receiver close to your body and use the body as RF signal shield. Then you start slowly turning around and see in which direction the signal is strongest. Then you move forward in this direction and check again.<\/p>\n

At some point the signal will be too strong and you won\u2019t be able to differentiate where the signal is coming from because the receiver is working in maxim sensitivity. In this case we need to dampen the signal to a level where we can distinguish the signal level in the different directions. Since we can\u2019t control the transmitter\u2019s strength, we have to lower the signal strength in the receiver. This can be done by lowering the receiver\u2019s sensitivity using one of the options available in Fox Hunt mode.<\/p>\n

Then with lower receiver\u2019s sensitivity we continue looking for the transmitter utilizing these techniques until we visually or audibly identify the transmitter\u2019s position.<\/p>\n

\"\"<\/a><\/p>\n

 <\/p>\n

While in TEXT mode or in CHAR (chart) mode you can change the frequency by pressing DOWN and UP or the receiver\u2019s gain (changing sensitivity) by pressing REC or STOP. But first select which mode for fox hunt you want to use – press DOWN for TEXT mode or STOP for CHART mode:<\/p>\n

 <\/p>\n

TEXT MODE:<\/p>\n

In text mode the signal strength is displayed with numbers and signal indicator.<\/p>\n

\"\"<\/a>1. RSSI: – packet\u2019s signal strength. Lower values indicate lower signal strength, note the value is negative
\n2. FRQ: – current center frequency, it can be changed by pressing DOWN and UP
\n3. #: – a code, representing the center frequency
\n4. LNA GAIN \u2013 receiver\u2019s gain (amplification) \u2013 Lower values mean less amplification, thus lower receiver\u2019s sensitivity. Note that the value is negative. The gain can be changed by pressing REC or STOP<\/p>\n

CHART MODE:<\/p>\n

In CHART mode, the signal strength is displayed as a graphic. In this mode is displayed not only the center frequency but also several hundred kHz above and below the center frequency. This mode has slower response time and it\u2019s more suitable for overall channel occupation assessment than actual Fox Hunt.<\/p>\n

\"\"<\/a>1. #: – a code, representing the center frequency
\n2. G: – LNA GAIN \u2013 receiver\u2019s gain (amplification) \u2013 Lower values mean less amplification, thus lower receiver\u2019s sensitivity. Note that the value is negative. The gain can be changed by pressing REC or STOP
\n3. current center frequency, it can be changed by pressing DOWN and UP
\n4. packet\u2019s signal strength. Lower values indicate lower signal strength, note the value is negative<\/p>\n

 <\/p>\n

PC SOFTWARE AND FIRMWARE DOWNLOAD:<\/strong><\/p>\n

LoRa_GPS_Tracking_Main_App.zip<\/a> – User Program
\nLoRa_GPS_Tracking_Bootloader_App.zip<\/a> – Firmware FLASH program<\/p>\n

USB_Bootloader_FIRMWARE.zip<\/a> – Bootloader Firmware for PIC18F26J50<\/p>\n

TX_1_06_26MHZ.zip<\/a> – Transmitter firmware for latest 26MHZ TCXO version<\/p>\n

RX_2_08_26MHZ.zip<\/a> – Receiver firmware for latest 26MHZ TCXO version
\nRX_2_09_26MHZ.zip<\/a> – Receiver firmware for latest 26MHZ TCXO version<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

After I made the GSM-GPS tracker, I\u2019ve realized that the cell coverage is usually not available at sites where rockets are being launched. For a while I\u2019ve been thinking of making an independent from the cellular network tracker for rockets, planes etc. With the LoRa SX1278 chips this became an easy task. TRANSMITTER Transmitter part […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"gallery","meta":{"footnotes":""},"categories":[9],"tags":[54,65,67,68,64,66],"class_list":["post-2501","post","type-post","status-publish","format-gallery","hentry","category-electronics","tag-gps","tag-gps-tracker","tag-long-range","tag-long-range-tracking","tag-lora","tag-sx1278","post_format-post-format-gallery"],"_links":{"self":[{"href":"http:\/\/www.blog.exrockets.com\/blog\/wp-json\/wp\/v2\/posts\/2501","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.blog.exrockets.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.blog.exrockets.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.blog.exrockets.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.blog.exrockets.com\/blog\/wp-json\/wp\/v2\/comments?post=2501"}],"version-history":[{"count":30,"href":"http:\/\/www.blog.exrockets.com\/blog\/wp-json\/wp\/v2\/posts\/2501\/revisions"}],"predecessor-version":[{"id":2719,"href":"http:\/\/www.blog.exrockets.com\/blog\/wp-json\/wp\/v2\/posts\/2501\/revisions\/2719"}],"wp:attachment":[{"href":"http:\/\/www.blog.exrockets.com\/blog\/wp-json\/wp\/v2\/media?parent=2501"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.blog.exrockets.com\/blog\/wp-json\/wp\/v2\/categories?post=2501"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.blog.exrockets.com\/blog\/wp-json\/wp\/v2\/tags?post=2501"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}