No radio waves emission on Lopy4

[cyby]

Hello,

I bought a Lopy4 card with the V3 expansion card to connect to Lora in LoraWan mode. I also have a gateway to make a private network.
I updated the firmware of the lopy4 card by specifying the 868Mhz frequency band.
I used the Lorawan example with OTAA activation to program the card.
I had two experiments, one with the private gateway and the other with The Things Network.
In the first case I used a personal AppEUI and AppKey declared in the gateway and
in Lopy4 and in the second case I used the values provided by TTN after account configuration and declaration.
I didn't succeed in connecting, the Lopy4 looped permanently on'lora.has_joined()'.
I used a field meter to measure the radio emission on the Lopy4 antenna and I get 0 v/m !
I used another antenna and another Lopy4 card and I have the same result!
It seems there is no radio emission.

Is there a step I missed to validate radio emission ?

Or any other idea?

Thank you for your help

[robert-hh]

@cyby After calling Lora.join() you should see the join messages every 15 seconds. The RF signal itself is short, depending on the SF setting just a burst for 70 ms at SF7 (default) up to about one second for SF12, and the power is low, 20 mW max. I do not know the sensitivity of of your field meter, but it has to be able to capture this signal.

[cyby]

Hello
Thank you for your answer

My Champ Meter is very basic and its accuracy is about 1v/m.
I did a new test with an SF of 12 at initialization and I don't see any manifestation at the antenna either . My gateway generates 50 v/m at about 50cm and I imagined that this would also be noticeable on the Lopy4 at least during its activation sequence.
If I measured the electric field it is because I can't connect to either my gateway or TTN and I think I have met all the conditions: DevEUI declaration on the Gateway/Server side, matching of AppEUI and AppKey between the gateway/server and the device.
Moreover the example provided for the Lopy4 is very clear and simple!
CT

[robert-hh]

@cyby Even when DevEUI and AppEUI are wrong, OTAA join will send the join requests. Only it may not get a response.
You may try also ABP for initialization. Then you can send arbitrary messages at the pace you like.
And just for confirmation on simple question (and I'm a little bit shy to ask): did you connect the antenna to the right U.FL connector?

[cyby]

@robert-hh
No problem for the question about antenna :)

Yes, I connected it.
I have experience in radio, not LoraWan. I know that it is destructive to transmit without load (antenna) connected to the radio output amplifier.

I'm going to try ABP activation.

Thanks

CT

[jcaron]

@cyby I think @robert-hh meant the right connector among the 3 présent on the board (there’s one for WiFi/BLE, one for 868 and one for 433 MHz). It’s easy to mistakenly connect the antenna to the wrong one.