The amateur radio corner

exactly… that’s why its interesting

Sorry for my wrong explanation.
I was aware that full diversity reception/as known in GSM BS/ is not feasible at this moment.
I’ve ment the following setup

  • Two Rx antennas at the same direction 90 degree polarized.
  • Two feeding cables
  • Two receiever connected to antennas – receivers collect packets and RSSI
  • One mobile transmit node with GPS on it – Hardware is ready/Arduino Atmega 328 SX1278/spi module + GPS+ two yagi antennas/. I’m busy with software and second yagi
  • At the end I compare and combine the two message streams.

Does it make sense? If yes I can make this measurement and share it.
Any proposals, remarks and concerns are welcome.

To be polarization independent I plan on using a Skew Planar or cloverleaf antenna on my single channel gateway.
I’ve build a Skew Planar antenna, but it wasn’t quite resonant on 868. By touching the antenna on one “leaf” I found out the reflection attenuation (VSWR) improved a lot. So the next experiment is to build a cloverleaf antenna.


As a ham radio operator I have been working lately on a TTN integration to APRS. This is the Automatic Positioning Reporting System that is used amongst radio amateurs to display the GPS data of their mobile rigs or handhelds on e.g. or

I have succeeded in creating two RestAPI endpoints so that my GlobalSat tracker is now displaying my position when the lora signal is received by wether a TTN gateway or WirelessThings gateway. If you do a search for ON3ZOE on those websites then : ON3ZOE-1 means received by TTN and ON3ZOE-9 means received by WT

Nice piece of work where loraWAN meets APRS.
73s de on3zoe


Cool work there.
I like the integration idea of this. Would you be so kind to share info about the APRS api details?


Hi All.
So I have decided to give LoRa APRS a go here in Cape Town.
All the Information about my setup is here:


“LoRa Phy Synch Word: 0xf3”

mmm, World of pain there.

Do you know for sure if that syncword is valid, the current understanding is that they may not exceed 0x7F.

Not having a valid syncword can cause interoperability issues with SX126X devices and\or loose you receiver sensitivity.

Granted Semtech do not appear to have released full details, but they were asked back in November (by me) to comment.

As yet no reply.

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Not my cup of tea, but: does the following partial explaination help?

The MSB leftmost nibble 0xF in 0xF3 indeed does not seem to comply with the first rule. (But again: not my cup of tea.)

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Thanks for taking a look and the comments, good to know.
This library is a little old now. I suppose there will be a few libraries to update regarding this.
Im going to start with coffee then;)

You would assume that Semtech know the full answer to this, so I wonder why they are so reluctant to tell everyone else ?

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The interoperability bit (with SX126X devices) is in itself easy to check.

I did use my link test software, which works on a combination of SX127X or SX126X devices, to carry out checks on certain combinations of sync word and did indeed see receiver sensitivity differences.

Hi LoRaTracker, Thanks for spotting the sync word issue, it was a typo and it has been changed to 0x3f

For both 0x3F and 0xF3 the nibble 0xF is not in the valid range of 1 thru 7?

(That is how I read the first and second rules. But you know I’m not an expert, and I don’t even know if one needs that compatibility.)

OK; well with a SX127x syncword of 0x3F and a SX126X syncword of 0x34F4 the comms works at least, though based on the details Semtech have been prepared to reveal so far, it maybe should not.

Have you carried out a receiver sensitivity check, say comparing just the SX127X comms with a syncword of 0x34 versus 0x3F ?

I guess there should be some kind of agreement as to which sync word should be used in Ham Radio?

Indeed, and one that has been tested.

I have the software tools (for SX126X and SX127X devices) that would allow for me to check the changes in receive sensitivity against particular syncwords and interoperability of course.

I have been involved in Amateur radio projects in the past.


Hey, The outcome of your research will be interesting.
Here is the group where I think specs are about to be discussed


I finally set it at 0x34 just to know it will work for the time being.
I now have another LoRa APRS IGate setup on 869.200 MHz connected to Callsign: CHIRP
Yes ISM, power and duty-cycle setup and now for some coverage testing…

Excellant plan.

Its not an on topic discussion for TTN, since the sync words for that are well known and tested, but I do still find it surprising that the full details of valid or not syncwords are apparently being kept secret.