LoPy Antenna Setup / Installation

[bartvandeenen]

@bartvrancken
Ok, I did run lorawan, without the antenna (well it was actually on the wrong connector!).

So can I tell if the radio chip is broken ? wifi runs fine, is this the same hardware? Does wifi interfere with the lora radio? Where can I find this info?

Greetings

[Xykon]

@bartvandeenen According to the specification sheet LoRa is using a Semtech LoRa transceiver SX1272 while Wifi/BT is using Espressif ESP32 Dual Core Microcontroller,

Not sure how the Semtech transceiver can be tested other than sending data between two LoRa devices.

[bmarkus]

@bartvrancken said in LoPy Antenna Setup / Installation:

running without antenne might break your radio! never turn on without antenna!

I don't think transmitting without antenna you can break the LoRa transceiver. I'm using gateways and devices without antenna many times for testing or just by accident with no issues (not LoPy but others with the same Sx127x chips).

[bmarkus]

@Xykon said in LoPy Antenna Setup / Installation:

@bartvandeenen According to the specification sheet LoRa is using a Semtech LoRa transceiver SX1272 while Wifi/BT is using Espressif ESP32 Dual Core Microcontroller,

Not sure how the Semtech transceiver can be tested other than sending data between two LoRa devices.

If you want to see the transmitted signals on the physical level you can go for an SDR (software defined radio) with a free SdrSharp software and a cheap DVB-T USB stick (RTL)., see http://airspy.com/

For LoRa test you need a proven, working LoRa device instead of two LoPy, at least in this stage. There are many vendors, e.g. Microchip's http://www.microchip.com/wwwproducts/en/RN2483 This module requires only a serial terminal and you can configure, send, receive with simple text commands. There are evaluation boards also with sensors and USB interface with this chip to connect to Linux, Windows via USB serial. Or the mikroelektronika click module http://www.mikroe.com/click/lora/

[borjam]

@te-bachi RF stuff requires some care. So I would recommend you to always install a proper antenna. Some transmitters can be damaged without one, or some circuits can misbehave due to interference. At the end of the day, the way to avoid unpleasant accidents and paranormal phenomena is to keep the simple rule: antenna always connected.

If you don't want to install an antenna, use a cheap 50 ohm terminator with a SMA connector. I would tell you to verify that it supports the transmitter power, but 14 or 20 dBm won't be an issue :)

Hint to Pycom: it would be a good idea to sell an accessory kit with, say, a couple of terminators, a couple of good quality coax cables terminated in SMA connectors and an assortment of attenuators. There are cheap 20, 30 or 60 dB attenuators available nowadays, and in case of doubt it can be really helpful to find out wether interference or bad software is causing problems.

[rskoniec]

Just wondering - what if I'm not using network.LoRa in my project - connected LoRa antenna requirement is still an issue?

[borjam]

@rskoniec said in LoPy Antenna Setup / Installation:

Just wondering - what if I'm not using network.LoRa in my project - connected LoRa antenna requirement is still an issue?

It won't transmit if you don't use it, so it shouldn't be an issue. Still, it is good practice to always "keep holes properly plugged" ;)

Just a healthy habit.

[LoneTech]

@rskoniec That should be fine. You can shut the LoRa radio down with network.LoRa(power_mode=network.LoRa.SLEEP), but it should be OK to just not transmit.

[rskoniec]

@borjam @LoneTech Thanx :-)

[SakshamaGhoslya]

@borjam "Using the LoPy hardware without antenna can harm"
Can you please elaborate it little bit?
What kind of signals can harm the hardware?
How will they harm it?

[livius]

@SakshamaGhoslya
Starting without an antenna may damage the hardware

[bmarkus]

@livius said in LoPy Antenna Setup / Installation:

@SakshamaGhoslya
Starting without an antenna may damage the hardware

Regarding the LoRa part (SX127x), transmitting w/o antenna will not damage the device. Even it is necessary to use it w/o antenna if you are experimenting two LoRa devices close to each other to avoid loss packets, overriding receivers.

[livius]

@bmarkus
this was on Pycom documentation - i do not remember the exact place

[bmarkus]

@livius said in LoPy Antenna Setup / Installation:

@bmarkus
this was on Pycom documentation - i do not remember the exact place

And it is my personal experience working with Lora devices and gateways :)

[borjam]

@SakshamaGhoslya

Some wireless hardware can suffer damage when transmitting without a proper termination impedance. Also, it's possible to suffer some unexpected interference in other parts of the circuit due to stray RF.

For instance, a coworker had problems with a router last month. Its GbE port wouldn't work at 1 Gbps. It turned out the culprit was a 5 GHz wireless interface which didn't have an antenna connected. It wasn't being used but it wasn't disabled either, and its default transmission power was 30 dBm (1 W).

Although you won't likely damage the LoPy by operating it without an antenna. As a general rule, always keep healthy habits when dealing with RF equipment. So, use an antenna or a 50 ohm terminator It will never hurt, and you will make sure that your test results are reproducible. And you will avoid paranormal phenomena.

If you have overload problems try separating the units a couple of meters, use an attenuator and/or lower transmission power.

Regarding damage: when a radio transmitter is not properly terminated, part of the transmitted energy is "reflected" towards the transmitting circuit instead of being absorbed and radiated by the antenna. If the reflected energy is too much it can really damage the transmitter. As a minimum it can cause overheating.

I insist: even if the transmitter won't be damaged, develop the habit of keeping the holes plugged.

[bmarkus]

@borjam said in LoPy Antenna Setup / Installation:

@SakshamaGhoslya

Some wireless hardware can suffer damage when transmitting without a proper termination impedance. Also, it's possible to suffer some unexpected interference in other parts of the circuit due to stray RF.

For instance, a coworker had problems with a router last month. Its GbE port wouldn't work at 1 Gbps. It turned out the culprit was a 5 GHz wireless interface which didn't have an antenna connected. It wasn't being used but it wasn't disabled either, and its default transmission power was 30 dBm (1 W).

Although you won't likely damage the LoPy by operating it without an antenna. As a general rule, always keep healthy habits when dealing with RF equipment. So, use an antenna or a 50 ohm terminator It will never hurt, and you will make sure that your test results are reproducible. And you will avoid paranormal phenomena.

If you have overload problems try separating the units a couple of meters, use an attenuator and/or lower transmission power.

While you are right in general, my answer was specific to SX127x.

[borjam]

@bmarkus

Anyway the SX1272 datasheet states a maxium VSWR of 3:1 when transmitting at +20 dBm. (rev. 3, page 84) and a maximum duty cycle of 1%. In extreme cases it could lead to damage I imagine.

[GregS]

@borjam Hmm - thanks for the heads up re the 1% duty cycle @20dBm - I guess that's an added incentive for honouring network fair use policies. ;^)

[borjam]

@GregS A pleasure ;)

Moreover, I forgot. Even when not causing damage, overheating might cause signal distortion, which can be a tough issue to debug. I'm speaking in general terms once more, but better safe than pulling your hair out because suddenly you can't decode your transmissions properly.

[assia]

Hi @LoneTech I used lopy in LoRa mode without external antenna and now I have to add the external antenna and I want to know if I have to do a configuration in my code to select the external antenna.
Knowing that I found nothing in the documentation as for WLAN for example.