Big metal barn radio interference???

[nzbaxterman]

Hello
First post to the forum, but I've been using MySensors (with NRF24L01) for a few months now.

I'm having range problems between a sensor and a gateway. They're only 15m apart, with no obstructions, but they're both attached to metal/tin sheds. The sensor is on the side of a 2m high x 3m wide metal pump shed and the gateway is inside a 7m high 18m barn (like a giant aircraft hanger!).

I've tried various antennas on the NRF modules. Have also tried putting the gateway in a window, so there's only glass between it and the sensor.

All I can think is the giant metal barn is somehow reflecting the signal? If I put the gateway and sensor inside the barn, 15m apart, they work fine!

Any experience or ideas with sensors and gateways in giant metal sheds?

[mfalkvidd]

Welcome to the forum @nzbaxterman
Giant metal barns can also be called Faraday cages. They are very good at blocking radio signals.

[skywatch]

@nzbaxterman As @mfalkvidd has said this is not an ideal situation.

You need to place the antennas outside where they can 'see' each other. A pre-made length of coax and a small fixing will be required. Try to think of ways to keep the coax cable run as short as possible as this will be a big help with the low power levels we generally use.

If you can put the whole radio module outside in a weather proof box then that would be another option.

[sundberg84]

@nzbaxterman - I had the same issue with a power meter inside a metal box. I drilled a small hole trough the box, put the radio on dupont cables and outside the box and voila, worked great.

[nzbaxterman]

@skywatch said in Big metal barn radio interference???:

@nzbaxterman As @mfalkvidd has said this is not an ideal situation.

You need to place the antennas outside where they can 'see' each other. A pre-made length of coax and a small fixing will be required. Try to think of ways to keep the coax cable run as short as possible as this will be a big help with the low power levels we generally use.

If you can put the whole radio module outside in a weather proof box then that would be another option.

Thanks @skywatch I'll experiment some more with different radios and antennas outside the barn. It's a bit frustrating because the barn has sensors in it, and I plan to have several sensors in opposite directions outside the barn. There's the pump shed 15m outside in one direction and a water tank on a hill 200m in the other direction.

I think I'm going to need sensors, acting as repeaters, on all 4 corners attached to the outside of the barn!

[skywatch]

@nzbaxterman You are welcome - It's a bit difficult to imagine the setup you want, but here a bit more to try and help.

1. All sensors in the barn will need to communicate with 'something' in the barn. Due to all metal walls you may get reflections that will affect signals so moving antennas 20mm at a time to try and find the 'sweet spot' will probably help.

2. Outdoors a 200m run will need a 500mW Nrf24l01+ or you could use lora radios. With the nrf it would be cheap and good to use a yagi (directional) antenna just for this link. You will want a yagi mounted at the barn and at the water tank pointing directly at each other. A helping hand an some walkie talkies would make this reasonably easy!

Mount antennas a high up as you can and avoid any obstacles in the path between antennas (including trees).

Let us know how it turns out!