I got a [Nordic FOB and a [nRF24L01+ Module with Chip Antenna with the idea that I could use it in my home as an automation controller but first looks on range have been disappointing.
I have the nRF24L01+ Module setup with the example firmware on my stk-500 and have been testing the devices and it seems like max acceptable range is 15’ indoors, aka awful. The room the receiver is in has a cinder-block wall dividing it between the rest of the house but I thought for something that boasts 100’ LOS range that wouldn’t be too much of an issue.
I’m wondering if there is just something im doing wrong or overlooking. Are there any tips or things I should check (settings?) with these modules to get some more range out of them? Would getting the [module with the SMA connector and running an antenna to the other side of the cinder block wall help?
Leon’s right: Chip antennas are lossy, but we like small!
theatrus:
Cinder block walls will kill most high frequency signals. Even normal drywall is a good shield.
You can do a line of site test outdoors, just make sure to elevate the equipment.
I disagree - drywall attenuates about 2dB per layer, 4dB per wall, at 2.4GHz. The line of sight path loss is many tens of dB. So 4dB is relatively small.
Block walls, if hollow-core, are not too bad; about 8dB or so. One with poured concrete interiors are higher.
There’s a NIST database of the attenuation vs. frequency for common construction materials. My comments relate to this and to my experience and careful measurements.
Transmitter’s Power in dBm (1mw = 0dBm, log scale) Out plus antenna gain (chip antenna about -2dBi), minus free space path loss (distance, per the physics forumla) + receiver antenna gain if any, less misc. losses for cables = received signal level. These low speed 2.4GHz data radios need anywhere from about -105dBm to about -90dBm to get a decent bit error rate. To this, allow margin for fading.
These budgets, used with some care, are usually fairly accurate, unless you have some very odd construction materials. This applies to indoors.
I did a range test with the fob and chip and got 2-3 meters indoors through a brick wall, and a good 6 meters without a wall and ran out of room to test.
The SMA duck antenna with the fob got through 4 walls and over 12 meters and again I ran out of room to test indoors. I’ve been trying to get around to doing an outdoor test but very busy with work at the moment.
To improve the data range try enabling AA, and lowering the data rate to 1Mbps as 2Mbps will reduce range a fair bit.
One more thing to pay attention to. Any Wifi signal around 2.4gig may raise the noise floor, and make the receiver seem less sensitive. Try a few channels, and see if there is some local interference that is frequency specific. I abandoned 2.4 for 900 MHz for long range apps a couple of years ago. Still use it for close in work though…
I am running 2 wifi APs in the house so I’m sure that’s not helping either.
I would love to use a 900mHz module, or even the 313 or 435mHz ones but SF doesn’t offer any key-chain FOB for them. I’m looking for a minimal effort, long battery life type thing for that part, so I’d like to avoid having to design and make one myself because I don’t have the capability to make such at thing.
I have 2 APs also and it doesn’t effect my default nordic config. I noticed when using the Xbee my Wireless Router was actually running on a nordic 2.5 old firmware so when I first tested Xbees I was automatically connecting to my router without realising, so I presume the protocol will be nothing the my nordics firmware so any noise would probably be discarded by the underlying demodulator pretty quickly.
With way, with the duck antenna the range was not an issue at all so I would try that. Also, 900Mhz is banned in some states so not as universal.
I just tried the module with a 5dBi duck antenna and the range is still pretty bad. The cement wall seems like it still pretty much blocks everything. Even at 25-30’ with 2 interior walls (drywall) between the FOB and the receiver reception is ~50% when you hold the FOB in a sweet spot and 0% otherwise.
I guess this thing was meant to work LOS outdoors, not indoors. I’m going to have to figure something else out. Thanks for all the input.
I have the nRF24L01+ Module setup with the example firmware on my stk-500 and have been testing the devices and it seems like max acceptable range is 15’ indoors, aka awful.
Data sheet says transmitter is 0dBm (1mW). Chip antenna is perhaps -2 or -3dB gain. So radiated power is perhaps 1/2 mW. With some antenna gain, it'll be better. But getting more than 3dB gain or so with a small antenna is not viable.
There are better solutions of course, in the $20-30 per module range. IMO, you’re better off using one of the many 802.15.4 modules (Digi, Jennic, et al), and choose the Tx power supported by the module based on your use case. Not proprietary air interface.
Less loss in penetrating masonry at, say, 433MHz, but here there aren’t any standards like '15.4. Consider Linx, Inc. modules. Easy to use.
I did more range testing at weekend with the FOB and the duck antenna and chip antenna.
Outdoors the chip antenna got about 20 meters in open air before failing. The duck antenna got further than I could see with my eyes so I need another person to give me a hand to do that open air test.
As for intererence. I tested the unit going through a car, from end to end, and side to side. The metal has a much more dramatic effect on the wireless than the bricks, as the chip antenna could only just about get through from door to door of a car (standing on the outside with the chips next to the middle of the door). The chip antenna failed to get from end to end (number plate to front number plate) however the duck antenna managed that… just about.
The next tests I plan to do are with both reciever and transmitter having duck antennas, which should give the best range possible. I will report back when I have tested that.
angelsix:
As for intererence. I tested the unit going through a car, from end to end, and side to side. The metal has a much more dramatic effect on the wireless than the bricks, as the chip antenna could only just about get through from door to door of a car (standing on the outside with the chips next to the middle of the door). .
Jargon: "Interference" commonly means, in RF-land, transmissions by other devices that degrade the receiver's performance. Or multipath (we'll go into that some other time).
“Attenutation” is the term for obstructions in the path from transmitter to receiver that reduce the received signal strength.
Be aware too that the chip antennas are somewhat directional. As you rotated it in 3D, sphere-like, you’ll see large changes in received signal strength.