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Thread: Improving range between two nrf24l01+?

  1. #1

    Improving range between two nrf24l01+?

    I've seen a bunch of people have been using the nrf24l01+ to get ranges of 10 meters (or more) and am vaguely perplexed cause in my tests I haven't gotten anything remotely reliable over about 16 feet. This, mind you, is if I rawdog it with the pcb antennas hanging out facing each other. If I seal them up in the pretty thin plastic cases of the devices they reside in, the reception is rubbish unless I extend the pcb trace to outside the case with a little jumper wire. Even at around 10 to 15 feet, they are very directionally sensitive, so packets will start getting lost if I'm facing away from the receiver. This is all in wide open space too, a big garage with no obstructions.

    I've got em set at PA_MAX, have made sure to powerUp() but didn't really find anything else in the documentation that seemed potentially helpful. Mainly I'm just wondering if people really are getting 30+ feet with two nrf2401's or if they have a more powerful reciever station or something like that. I've seen some modding the antenna: http://electronics.stackexchange.com...ing-an-antenna
    but it doesn't seem like everyone's doing that.

    Granted, in my current setup I only actually need about a meter, so this isn't truly a big deal at the moment, but still, it would be nice to have a totally reliable 15 foot radius. So I guess I want to ask, does anyone have any cool nrf24 range maximization tips?

  2. #2
    Senior Member+ defragster's Avatar
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    I wonder if you have a bad module - or a power problem? I just found a site "NRF24L01 real life range test" saying they vary but in clear air they are at 50M or above to 80M, with the right one. Have you dropped the transmit speed and tried small payload packets of like 8 bytes? I saw other postings saying you need a cap on the power to make sure it doesn't drop. http://arduino-info.wikispaces.com/N...1-2.4GHz-HowTo

  3. #3
    SWEEET! thanks for the help man, boosted my range up to a solid 50 feet by using setDataRate(RF24_250KBPS) and setting the payload size to 6 (it had been 8). In some extra payload tests I got much more range with 2 bytes, something like 100 feet before I ran out of yard. Most importantly I'm not losing packets at 5-15 feet anymore, which had been a depressing state of affairs. I'm glad I asked before calling this project done.

    Also, I didn't solder a capacitor onto the module like some people have suggested, it's being powered from the 3.3v rail on a T3.1. I've got a 10cm wire extending the pcb printed antenna (just glomped right onto the end of the zigzag), not sure how that factors in.

  4. #4
    Senior Member+ defragster's Avatar
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    Glad that worked out! Range is important nRF24 or ESP-8266. Yesterday I was pacing my driveways and trying to figure how (much of) two 500 feet parallel drives in the woods I can cover that are 150 feet apart with trees in the middle and no power, or much sun. I'd like to know when the mail comes to the street and when somebody comes up a driveway.

  5. #5
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    I've got a 10cm wire extending the pcb printed antenna
    That might make things worse. Try it with and without the wire to see if there's any effect at all.

    Pete

  6. #6
    Senior Member+ defragster's Avatar
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    I was going to suggest taking off the wire too - those PCB runs are proven effective it seems 'when properly done' - adding anything would seem just a way to detune them. Saw another summary test where they were better than ceramic - though another anecdote said the ceramic can be better - maybe more directional?

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    ceramic antennas for 2.4GHz - made for Bluetooth. Ones I've assessed in depth - have odd radiation patterns. On average, directionally, the gain of these is about -6dbi. Bad.
    If you can disconnect it and use a wire antenna (about 1/4 wavelength), it'll be better, if the antenna is kept vertical.
    On-PCB etched antennas - tiny bit better than a 1/4 wave wire antenna.

    If you can equip the radio with an SMA connection, then buy and use a 5dBi antenna on the immobile end of a link, you'll see improvement.

    But the real range story is using 2.4GHz and low power (10mW or less) - rather than a sub-GHz radio in 868 or 915MHz band, or perhaps 433MHz. Laws of physics say these subGHz bands have a lot lower loss for a given path length. And non-line-of-sight paths work better at lower freqs. And radios like the HopeRFM69HW get you 300m + range as a rule, depending on how much path obstruction there is.

    the nRf24L01 spec says 4dBm tx power. that's about 2mW (0.002 watt). Penalize that with a negative gain antenna and range goes down more. Penalize more with a 1 or 2Mbps GFSK data rate= less range. And competition for air time with 802.11/WiFi in the same band with its 20MHz wide signals and 30-100mW (0.030W) signals. Low data volume telemetry needs to use like 4Kbps or so, in a 10KHz wide channel in sub-GHz.
    That's where the range comes from.

  8. #8
    Thanks for the detailed info! I had put the antenna extension on there because once I first sealed up the board in its thin plastic box, the wireless was completely belligerent from pretty much any distance. Maybe now that I've improved the range via other means, I'll try removing it. I'll definitely check out some sub ghz radios in the future, if I ever need for more substantial range. My wireless projects are really just music/MIDI based so although it would be pretty high class to be able to play a synth from 100 yards away, I probably dont need that for the moment

  9. #9
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    If you use the add-on antenna, somehow you need to properly disconnect the on-PCB antenna. Both at once will create an impedance mismatch and degrade radiated power and thus range.

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