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  • Author Author: aswinvenu
  • Date Created: Date Created
  • Views 12703 views
  • Likes 10 likes
  • Comments 13 comments
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External Antenna for Raspberry Pi 4

aswinvenu

Introduction

     For one of the Raspberry Pi projects I have been working on had this specific requirement for an external antenna. The entire Raspberry Pi 4 needs to be placed inside a metal box. So external antenna was the only option left for me to make the Bluetooth and WiFi to work. I had two choices, One to use the compute module 4 and use the IO board or use a regular RPi and somehow add a UFL/IPEX Connector to the PCB. Considering the cost and availability I preferred to try the second option.

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    On a closer inspection of the WiFi/BLE Module area, We can see a small provision where a UFL/IPEX Connector can fit. Ofcourse there are no expose pads for an UFL/IPEX connector. We need to create one ( Atleast the ground pads ).

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Step 1

  Remove the solder mask and prepare a nice and clean exposed copper pad for soldering the UFL/IPEX connector.

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Step 2

    Cut the trace which goes to the on PCB Antenna and solder a 0201 0E resistor like shown below. 

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Step 3

   Remove the capacitors used in the PCB Antenna.

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Done! I connected an IPEX 4dB antenna to the my RPi 4 for a quick test.

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Result

Everything works fine and I am getting roughly 4- 5dB difference compared to the stock PCB antenna.

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My router was atleast 5-6 meters away from the RPi and there was a wall separation.

Parents

  • Hi!

    I guess you had little choice since the box was metal. It could also be worth using a Pi Compute Module instead since that comes with the RF connector already fitted. There are "baseboards" that the compute modules can plug on top of, to give the same form factor of the original Pi.

    For anyone thinking they want to do this on a Pi, it might be worth pointing out that there is a risk of exceeding the allowed power level (which is why they have the solder resist on that connector), and it's a quick way to damage the board too, since an 0201 resistor is not normal : ) That took some skill to do, not easy the first time around.

    Anyway, good work, glad it worked out for your need.

  • in reply to shabaz

    I thought of using  CM4IO Board and  CM4. But unfortunately, I couldn't fit everything inside the Metal Box ( Junction Box ). Now the other options I have is to use some waveshare boards. Which I am still exploring. The only advantage I can see using the regular RPi is my procurement becomes whole lot easier. But still exploring.


    "i, it might be worth pointing out that there is a risk of exceeding the allowed power level (which is why they have the solder resist on that connector), and it's a quick way to damage the board too"

    You meant the TX Power ?

  • in reply to aswinvenu

    I believe the standards define radiated power (i.e. not transmitter power) for WiFi, so for that reason often the antenna is either not replaceable, or has no RF connector, or uses a funny connector (RP-SMA, etc). Regarding the 'quick way to damage the board', there's perhaps just a small risk of that at the power levels involved, but I wasn't thinking of that; that comment was in regards to the next bit of the sentence, i.e. the 0201 resistor. Lots of people have huge soldering irons, and may end up just lifting pads due to heat, and losing the 0201 resistor inside the solder blob anyway!

  • in reply to shabaz

    Okay got it! You meant Radiated emissions under IEC 61326-1 and CE/FCC conformity right?

Comment Children
  • in reply to aswinvenu

    That's slightly different, that's unwanted emissions (but also relevant for products for sure). Every country has a regulatory body for wireless, e.g. in the USA it is FCC, and in the UK it is Ofcom (those are the only ones I know), so their websites will have the information, but it can be hard to find.

    For instance on the ofcom site, there's a PDF doc which mentions the amount of radiated power allowed (and there will be other restrictions too). So for instance, with 5 GHz WLAN, there would be the particular restriction below (but it would need an expert at navigating through their sites to be sure; not me!). 

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    In that doc, they list it as EIRP, meaning that they expect the antenna to be taken into account. There are online calculators to experiment with (e.g. https://m0ukd.com/calculators/erp-eirp-calculator/ ); for instance, if you had a transmitter of 100 mW, and no other loss and (say) connected to an antenna labeled 6 dBi, then the radiated power (there are several ways to measure it; they are using EIRP in the PDF document, so that is the box to look at in the screenshot below) would be almost 400 mW, so that would exceed the allowed limit in that example. If the user wished to stay within the 200 mW allowed limit in that case, they would need to either reduce the transmitter power to 50 mW, or instead, change the antenna to one that is 3 dBi max.

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