I’ve got almost all of the pieces parts spec’d out for the nRF2401 circuit in their documentation, except for the inductors b/c I can’t seem to find parts with the same tolerances.
Can anyone suggest a supplier for the pieces? Does anyone have a PCB design they’re willing to share?
Thanks,
Jeff
Hi Jeff,
As you know, we do things a bit differently around here. The manufacturer will use the highest quality components. We managed with some lower tolerances and cheaper parts. We use digikey primarily for all our parts and Mouser for some odd things (USB connectors, headers, Abracon xtals, etc) where they are significantly cheaper.
-Nathan
Nathan,
Thanks; I found part numbers for almost all of what they recommended from Mouser and was going to check Digikey for the rest–I guess I did it backwards! I guess I must like making things hard on myself if I’m to build a TxRx with original components rather than using the trf24g I already have! I guess it’s just the challenge.
You mentioned many blown boards, etc; can you give any words of advice that you may have learned from your experience in building the transceiver from the Nordic schematic?
Thanks,
Jeff
Few things we’ve learned:
Make sure you use a crystal and not a resonator.
The antenna is pretty forgiving. It’s easy to get the board to emit over a short distance of 5-10ft with no antenna at all. It’s next to impossible to design a board with antenna to go anywhere near the 200m? limit. 100ft is not too much of a problem tho.
The QFN package can be hand soldered with a modified footprint.
A low noise voltage regulator helps. Decoupling helps. That’s about it.
-Nathan
This is my first post, this group looks like fun.
Has anyone tried one of the 2.4 Ghz “chip antennas” with the Nordic chips?
Tried one without any added benefit but that’s probably because my matching network was wrong. I just discovered this 2.4GHz chip antenna on digikey : ANT-2.45-CHPCT-ND (uber cool).
Unfortunately I am not savvy enough to design the matching network from the nRF2401A to this 50Ohm chip antenna. Does anyone have any experience designing these things or know of some software that would help?
It’s all black magic to me.
-Nathan
The folks best qualified to do the matching is obviously Nordic. Given the appropriate matching components, these chip antennas would appear to be the ideal low cost drop-in antenna solution. Do you have a contact at Nordic?
Just looking around, I've found nRF2401rev1_1.pdf, page 35 has a matching network for a 50 Ohm antenna, and on Linx's website they have an Excel spreadsheet (in their Support/Software section) for calculating the microstrip to use to the antenna. From what little (read: the words, and nothing else!) I know of this stuff, that seems like what's needed?sparky:
Tried one without any added benefit but that’s probably because my matching network was wrong. I just discovered this 2.4GHz chip antenna on digikey : ANT-2.45-CHPCT-ND (uber cool).Unfortunately I am not savvy enough to design the matching network from the nRF2401A to this 50Ohm chip antenna. Does anyone have any experience designing these things or know of some software that would help?
It’s all black magic to me.
-Nathan
*edit: To save you the trouble of the microstrip calculator, with the 0.062" FR4 boards from SparkFun, it looks like the microstrip should be 114 mils (0.114") wide, assuming I didn’t screw something up. 
The Nordic schematic is for a single ended monopole antenna. The chip antennas are differential.
Yep - all the SMiRFs (and the new MiRFs) have a recommended manufacturers layout.
We don’t really think for ourselves around here. Well, at least when it comes to microstrip 50ohm 2.4GHz antennas. :twisted:
-Nathan
jqp123:
The Nordic schematic is for a single ended monopole antenna. The chip antennas are differential.
Hunting through Google didn’t turn up much information about what the difference is - but are you sure? From the application note nAN24-01rev2_0:
nAN24-01rev2_0.pdf:
the schematic for RF layout with a single end connection for 50W antennas is presented. This is done using a differential to single ended matching network using 0603 size passive components.
That sounds like it’s saying the schematic (same one as in the datasheet) is for precisely this purpose; “differential to single ended”, unless I have it backwards. The Linx chip antenna does only have a single connection (the other end is NC and only used to secure it to the board according to the datasheet).
It sounds like I have everything backwards - I just need a little confirmation.
Nutter:
*edit: To save you the trouble of the microstrip calculator, with the 0.062" FR4 boards from SparkFun, it looks like the microstrip should be 114 mils (0.114") wide, assuming I didn’t screw something up.
I use a few linx technologies RF transmitters and receivers, along with their ‘Splatch’ planar antenna, and I find them to be exceptionally easy to use.
There’s a linx application note (for the LR series receivers) that for standard FR4 PCB material, in a 62mil width, the microstrip should be 111mils wide to give a 50 ohm impedance.
I’ve just ordered a full panel of boards from SparkFun with 111 mil microstripped traces, so I hope they’re right!
On an added note, the LR series tx and rx have a theoretical range ‘in excess of 3000 feet’
I’ve got 45 tx and rx pairs on their way from digikey, so I’ll let you know how the range goes with the 111mil traces.
sparky:
We don’t really think for ourselves around here. Well, at least when it comes to microstrip 50ohm 2.4GHz antennas. :twisted:-Nathan
He he…is that right? 
The Linx chip antenna does only have a single connection (the other end is NC and only used to secure it to the board according to the datasheet).
By golly, I think you’re right! I just assumed that it was a loop type since both ends are soldered.
I’m not certain who you could contact at Nordic about these chips, but I know that their NA distributor is Symmetry Electronics. They may be able to help you out with that. I think Symmetry may even have a place you can pick these parts up online as well.
See if you can find anything at:
Let me know what you find out.
I know that about 112 mils is correct for 50 ohms below 1 GHz.
A few mils either way is not critical. The FR4 dielectric may change
a little at 2.4 GHz but 112 mils should still be close enough unless
you have a long run.
He may not appreciate me giving out his name but I’ve received
good information from:
Jon Gunnar Sponaas, M.Sc.E.E.
Field Application Engineer, Wireless Communication Nordic VLSI ASA Vestre Rosten 81
N-7075 Tiller
NORWAY
<EMAIL email="jon.gunnar.sponaas@nvlsi.no">jon.gunnar.sponaas@nvlsi.no</EMAIL>
MJ:
I’ve got almost all of the pieces parts spec’d out for the nRF2401 circuit in their documentation, except for the inductors b/c I can’t seem to find parts with the same tolerances.Can anyone suggest a supplier for the pieces?
Jeff
Having worked with the nRF2401, the crystal is the most critical part.
I don’t know about the Abracon crystal SparkFun is selling without
a complete part number (can someone give us that?). My biggest
concern would be whether the load capacitance is too large. I do know
that the MA03057 which can be purchased directly from Golledge:
http://www.golledge.com/docs/products/xtl_sm/gsx433.htm
works extremely well. Remember that 16 MHz is being multiplied up to
2.4 GHz so a little bad at 16 MHz is a lot bad at 2.4 GHz. If you use the
50-ohm matching network of Figure 20 on the nRF2401A data sheet I
would recommend capacitors as Mouser (AVX microwave size 0603):
581-06035J4R7BBT, 581-06035J1R0BBT, 581-06035J2R2BBT
These are +/- 0.1 pF which in some cases is better than specd.
For inductors I don’t think you can beat coilcraft and I would use
0603CS-5N6XJBU and 0603CS-10NXJBU which are 5% tolerance.
If you want 2% tolerance the numbers end in GBU instead of JBU.
You can purchase directly from coilcraft and they have free samples:
http://www.coilcraft.com/0603cs.cfm
If anyone tries the chip antenna from DigiKey with this network, please
post and let us know how it works.
Abrcon Part # : ABMM2-16.000MHZ-E2-T
We’ve had good sucess with this SMD xtal. You’re right, the load capacitance is high, but we could not find a SMD xtal with the Nordic recommended max 12pF load. Indded, the one you spec’d is still 16pF.
Nice part though. Better stability than the abracon part. Any Xtal can be procured at any spec. The main thing for us at SFE is price. The abracon part at 1-$2 is a steal. A SMD xtal can easily run 5-$20 depending on tolerances.
My main point - the abracon part works. I imagine a better xtal, tighter tolerance parts, and a better matching network would increase the range nominally. Then again, a 2.4ghz SMA antenna would do wonders as well. The PCB etched antenna on the SFE boards works, but it’s a cost thing again.
What I’d love to see is a nordic setup with a Power Amplifier and an external Antenna. Talk about range…
-Nathan
Hey Sparky – I’ve done a couple prototypes of the nRF905 and nRF2401 with SMA connecotrs and Linx 1/4W whip antennas for a couple of my clients. They work great and definitely extend the range. Although we weren’t really looking for extended range, the best effect I’ve observed is that the packet error rate goes down quite a bit using whip antennas.
Using a “real” whip antenna is obviously more expensive than a PCB strip antenna but in my case we were after the best signal we could get with what was already there and cost wasn’t an issue.
Better packet error rate, eh? I wonder if it’s a BW thing…doubt it, but I’d love to get one of there on a network analyzer. If ever I could afford one of those.
Pete