SparkFun Forums

[Nullz]

Anyone have an example of the nRF24L01 connected to a power amplifier? I have been looking at the MAX2240 by Maxim. The MAX2240 is a 100mw or +20dB power amplifier for 2.4 GHz ISM GFSK modulated radios.

Can I connect the MAX2240 directly to the ANT1 or ANT2 outputs of the nRF24L01 without the impedence network? I think the impedence network is still required to match the 50 ohm impedence but I want to make sure. The MAX2240 datasheet says it can accept a 50 ohm transmission line but it doesn't say it has to be 50 ohms. I am not too familiar with impedence matching on RF.

Also, the MAX2240 datasheet makes it seem like it is unidirectional from RF input to RF output. Is this true? Meaning, if I use the MAX2240, I can only transmit and not receive?

Any info would be appreciated. If this little chip turns out to work well and is easy to use, I would love to see a 100mw MiRF v2 with RP-SMA.

Thanks!

Nullz

[brennen]

Here is a white paper by Nordic that details how to hook up the 2401 (the 24L01's predecessor) to an external power amp. I can't see any differences between this schematic and what you would do with the 24L01. Check it out at http://www.avantcom.com.tw/products/act ... b%2003.pdf.

As far as hardware, you have to use switches because, as you noticed, these RF amplifiers only go one way. The white paper I mentioned above shows how to do this. The matching network that is already present on all of the 24L01 breakout boards (MiRF-v2, etc.) is already 50 ohms, so you don't really need to worry about that part. Oh and this white paper also happens to use the MAX2240 that you mentioned, so it should be right up your alley.

[RonnyM]

Hittite makes some very easy to use 2.4 gig amps also. I believe the 308 puts out 60 mW in a SOT package. They even have a low noise preamp for the other side. You can use a submini balun for going to an unbalanced output. It will save board space and part count.
Ron

[caillyn]

The app note given by brennen has the RF switches controlled by the microcontroller connected to the NRF chip, so I think you will need to use the nrf24L01 with enhanced shockburst turned off ( nrf2401 compatible mode ) as the auto ack and retransmit features will automatically switch the 'L01 from RX to TX and vice versa.

[brennen]

The app note given by brennen has the RF switches controlled by the microcontroller connected to the NRF chip, so I think you will need to use the nrf24L01 with enhanced shockburst turned off ( nrf2401 compatible mode ) as the auto ack and retransmit features will automatically switch the 'L01 from RX to TX and vice versa.

You are correct. I overlooked this in my prior post.

[Sheng]

Hi Nullz,

This is interesting! RonnyM did a range test w/o PA viewtopic.php?t=8028
Would appreciate if you can let us know the range after you added in a PA.

Thanks!

Regards,
Sheng

[tastech]

I have recently been working with the nRF24L01 and a PA with approx 25dB gain. We measured our actual output at +22.5dBm (some losses from switches and coupling) and are using small monopole antenna from Antennova.

At this point with a fairly rough setup we are seeing 750 feet at 2Mbps and over 1000 feet at 1Mbps. At this range there is very little data loss so the range can be extended from this. Allowing "some" data loss we went beyond 1400 feet at 1Mbps.

Large obstructions such as vehicles or building have a significant impac on the range. Antenna selection also has a large impact.

At this point things are not fine-tuned, we anticipate another 2 to 3dB improvement in output power. We are also working on a frequency hopping scheme that we will implement before further testing.

[Nullz]

I have recently been working with the nRF24L01 and a PA with approx 25dB gain. We measured our actual output at +22.5dBm (some losses from switches and coupling) and are using small monopole antenna from Antennova.

At this point with a fairly rough setup we are seeing 750 feet at 2Mbps and over 1000 feet at 1Mbps. At this range there is very little data loss so the range can be extended from this. Allowing "some" data loss we went beyond 1400 feet at 1Mbps.

Large obstructions such as vehicles or building have a significant impac on the range. Antenna selection also has a large impact.

At this point things are not fine-tuned, we anticipate another 2 to 3dB improvement in output power. We are also working on a frequency hopping scheme that we will implement before further testing.

tastech,

Would you be willing to share your design or is this for your job? If you can't share schematics, would you be willing to atleast share what parts you used (PA and RF switch)?

Please let us know. I am very interested in this.

Thank you,

Nullz

[tastech]

Unfortunately this design is for work so I can't give away the details.

I can however tell you to take a close look at the PA's from California Eastern Labs. We have tested both the UPG2314 and the UPG2250 PA's and both work quite well. There is quite a bit of signal compression near the top end of the power output, but if things are scaled back a bit then all works very well.

We are considering making our module available for sale when we are done. It will have an integrated ceramic antenna and will be FCC, ETSI (lower power version), and IC approved in this version. We will also offer a non-approved version with a connector for an external antenna as well.