nRF24L01+: Improve range between PA+LNA+SMA antenna version and basic version

Projects Networking, Protocols, and Devices
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I've been doing some testing on nRF24L01+ modules, especially on range, and I like everyone I want more range.
The goal is to have a central hub with multiple sensors for use in house (with concrete floors, yay). Each sensor communicates directly to the central hub, so between a sensor and the hub 2 way communication should be possible. I want to use the PA+LNA with antenna - version in main hub, and the smaller modules with on board antenna for sensors.

To look at feasability I've done some basic range testing on them, and is is on the edge of fair connection. Meaning that if I look at the sensor furthest from the hub location, it has contact, sort of. Depending on where I stand, the exact antenna direction, and possibaly even the ether winds, I sometimes have no connection.
I'm looking for a decent way to make sure I have connection roughly everywhere. I already have set powers on max, caps soldered on all modules, set send retries to 15, and am using 250kbps data rate. Additionally I am using a 3.3v regulator on the PA+LNA module.

Can I get better sending/receiving capabilities on the central hub by changing the antenna for a "better" one? If yes, what to look for in such an antenna?

Alternatively can I improve connectivity by soldering a wire antenna to the basic modules (as described here). Exept I don't think I can implement this perfect dipole. A sollution I would rather be looking at is a flexible wire-antenna, that can be bent to fit the space of sensor installation (for example: bent around the inside of a 3x3cm enclosure). Or would that give worse than stock performance?

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Monitou:
ICan I get better sending/receiving capabilities on the central hub by changing the antenna for a "better" one? If yes, what to look for in such an antenna?

Possibly.

A lot depends on the regulations applying to your part of the World.

Adding 'better' antennas will increase the effective radiated power and there are very often legal restictions as to what you can do.

If the range with the nRF24L01+ is marginal then switching to a lower frequency module, 433Mhz for instance, could improve range considerably.

3

Monitou:
I've been doing some testing on nRF24L01+ modules, especially on range, and I like everyone I want more range.
The goal is to have a central hub with multiple sensors for use in house (with concrete floors, yay)

You have not told us what range you actually need.

Concrete is not good for 2.4Ghz wireless.

...R

4

I tried looking at local gurlations, but they are pretty complicated. For now I know somewhere between 25 and 100mW is legal, depending on the exact use, so that is 14 to 20dBm as max e.i.r.p.

Range I would want is up to 30m indoors with up to one concrete floor and 3 stone/concrete walls max. Though more range is more better, or at least gives more stable coverage and is less interference prone.

I do know 2.4GHz is not optimal, but these modules are easy to work with, well documented, and I finally understand most of the features/library. And if my wifi can do it, why couldn't these?

5

Monitou:
I tried looking at local gurlations, but they are pretty complicated. For now I know somewhere between 25 and 100mW is legal, depending on the exact use, so that is 14 to 20dBm as max e.i.r.p.

And since the power output of the nRF24L01+PA+LNA is, if I recall correctly, 20dBm, you cannot (legally) fit a better antenna.

The range you want seems optimistic to me in that environment, but since you have access to the actual location, why dont you just do a test and report back ?

6

Ah, yea, found the datasheet on another site (my seller didn't have it online). Seems max power is indeed 20dBm. But does changing the antenna change the dBm power?

With regards to just testing. That is sort of what I’m aiming for. But as I'm only vaguely familiar with antennas and the exact workings of RF communication, I would like to get some info first. I have little idea what to look for.

2.4GHz antenna’s I found do often have a dBi value that is their spec. But what is the “better” I’d be looking for? After all is a higher dBi antenna better? Or does it just shape the range to be more flat, and would a low dBi antenna be better to get a more spherical range?

Also I could just try to solder a wire on the basic nrf24l01+ module, but if the consensus is that it won’t matter, or I’d need to take into account something specific (shape, length, location, idk.). Just saying I’d rather not ruin my modules just for some random trial and error testing. Non-random testing is ok, but I’m not sure where to start. And like I said, the ideal dipole as in the link is not feasible for me.

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Monitou:
Ah, yea, found the datasheet on another site (my seller didn't have it online). Seems max power is indeed 20dBm. But does changing the antenna change the dBm power?

Say you used an 8dBi antenna, putting 20dBm through that would double the effective radiated power to 26dBm, 6dBm over the limit.

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I think you mean 6dBi antenna? Else I have no idea how 20 and 8 make 26.
Also how does this doubling of power work? Is it free, in the sence that all components do the same, exept you have more range? Does the amp physically supply more power? Is it more like beam focussing? (i.i.r.c. long antennas have flat disk-like range, and short ones are spherical) Or is there some other mechanic in play?

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Monitou:
I think you mean 6dBi antenna? Else I have no idea how 20 and 8 make 26.
Also how does this doubling of power work? Is it free, in the sence that all components do the same, exept you have more range? Does the amp physically supply more power? Is it more like beam focussing? (i.i.r.c. long antennas have flat disk-like range, and short ones are spherical) Or is there some other mechanic in play?

The limits are set assuming your using the simplest practical antenna such as a dipole or 1/4 wave vertical with radials, this is 2.1dBi.

Gain antennas focus the power.

10

I don't think I really understand what you're saying. Could you elaborate?

Also still looking for an answer on modding the on-board antenna.

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A very quick and easy test will be for you to place WIFI router, connected to the internet, where your Arduino is going to be, and then go to the rooms where your other Arduino is going to be and use a computer to access the internet using the test router. If this works, then there is a chance the NRF24 system will work.

Paul

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Monitou:
And if my wifi can do it, why couldn't these?

I wrote a Reply on this point earlier - it seems to have been lost. Anyway ...

If you can get WiFi to work over the exact same route I would expect the nRF24s to work.

  • Have you tried different nRF24 channels to see which works best?
  • Have to tried carefully orienting the antennas and making sure they are not near any metal that might absorb the signal?
  • Are you using the lowest data rate?
  • I suspect that putting a better antenna on the low-power modules would not offend the regulations - but I'm not an expert.

...R

13

Monitou:
I don't think I really understand what you're saying. Could you elaborate?

If 2dBi is the base antenna, then an 8dBi antenna is 6dBm more (2 + 6 = 8)

Also still looking for an answer on modding the on-board antenna.

If you are experienced in RF stuff, you might improve the antenna, or then again you might not.

I would not know without trying such a mod on that particular module to know what impact it might have on range.

But as suggested why dont you actually try out the modules you are using, that cannot be difficult, if they work OK in your situation then a lot of time will be saved discussing theoretical modifications or changes.

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Paul_KD7HB:
If this works, then there is a chance the NRF24 system will work.

Already did this check, but with my phone. And it works very well for the 2.4Ghz. But I'm having trouble getting it to work with the modules.

Robin2:
Have you tried different nRF24 channels to see which works best?

Yes, I have tried the default, 100 and 125, but could not really detect any differences

Have to tried carefully orienting the antennas and making sure they are not near any metal that might absorb the signal?

Yes, this does help, and this is the way I can get signal on modules on the outer perimiter of my wanted range. But it realy strongly depends on positioning, meaning that any touch while cleaning or so may break connectivity. So my aim is to make it a more robust connection by either improving the main hub (antenna), or the sensor modules (with onboard antenna, and no PA+LNA).

Are you using the lowest data rate?

Yup, all set at 250kbps.

I suspect that putting a better antenna on the low-power modules would not offend the regulations - but I'm not an expert.

Likewise, but i'm a bit stuck on what a better antenna would actually be. An actual sma antenna like on the main hub would probably work, but is unpractical for smaller builds, where the entire sensor + arduino + nrf24 module would fit in a 4x4x3 cm footprint.
Ideally itd just be a flexible wire that just fits wherever the sensor is put/built in. Though that would mean a bent antenna. Not sure how that effects range. The on board antenna is also a zig-zag pattern, the question is then if this has a tuned distance, or anything with that length will do. Antenna knowlage is pretty limited...
So I guiss my question on this part is, if I would put an antenna on the low power module, what would work, and what wouldn't?

srnet:
If you are experienced in RF stuff, you might improve the antenna, or then again you might not.

I know bits and pieces, but would not call myself experienced. But do not know enough to say something sensible about making an antenna. Was hoping to find some experience here.

But as suggested why dont you actually try out the modules you are using, that cannot be difficult, if they work OK in your situation then a lot of time will be saved discussing theoretical modifications or changes.

You mean try them stock? I have, and they barely do the job, but the ones further away sometimes dont have a connection. Hence this topic

15

You wrote:"Already did this check, but with my phone. And it works very well for the 2.4Ghz. But I'm having trouble getting it to work with the modules.".

What kind of phone do you have that works at 2.4 gHz with a central site to where you are testing your nRF24? If you are referring to your cell phone, they operate in the 800-900 mHz area and talk to a very powerful transmitter in the closest cell tower, probably through a window.

Paul

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Paul_KD7HB:
What kind of phone do you have that works at 2.4 gHz with a central site to where you are testing your nRF24? If you are referring to your cell phone, they operate in the 800-900 mHz area and talk to a very powerful transmitter in the closest cell tower, probably through a window.

A normal cell phone, but i'm looking at the connection to my local wifi, not the calling signal. So I'm looking at the connection to the wifi access point.

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WiFi systems have a lot of redundancy built in. You need the same in your nRF24 programs so that they can cope with a few missed messages.

...R