Raspberry Pi Zero W external antenna mod

It's fantastic that they included a place on the board to solder the component. Very thoughtful!

If you look carefully at the pad arrangement, it's more likely that the u.fl jack was there so the onboard resonant antenna could be connected to external test equipment for tuning. Removing the pads in the final board rev would've affected the tuning, so they left it. Using it for this purpose only requires moving the component 90 degrees, and it fits properly across the pads once you've done so. The 45-degree arrangement is clearly not what the pads were designed for, but it serves a purpose that's more useful to the end-user.

Its probably more likely that it was there for diagnostics and not removed. Although I do agree its quite useful that they left it there :)

It's actually there as a requirement for certification/regulatory testing. A conducted RF port is needed on the final product.

Thats Lotus, thats good info, well worth knowing.

Also in my experience RF stuff is static sensitive, so please be careful!
Maybe someone can figure out how to use the now-redundant internal antenna for triangulation or similar?
On certain chipsets its possible to specify antenna I or II so it might be feasible ?

The link resistor allows you to use the built in antenna or redirect the RF signal to the U.FL socket by turning the resistor 45 degrees

Ah. My bad, sorry. I see that the internal antenna is basically a special cavity inside the board so each unit is "tuned" correctly although the handy feature here would be further fine tuning using a tiny drop of UV set glue for those times you can't quite fit an external antenna in the unit. Protip, this is also handy for patching up damaged USB-micro connectors after resoldering, adding pink LEDs in place of the vanilla green/yellow and other micro-soldering mods.

Nice! However you should also probably change your Wifi network to not use ch13 (Google wifi channels for more info).

Only in the USA. There you can use it to hide you WiFi :)

I cant find anything that says that i cant use channel 13 in the UK, seems only the USA dont allow it?

Nice find! Thanks for sharing... This could come in very handy for some of those iOT applications in remote parts of the house that the W is going to fit into.

Shouldnt be too difficult to sort out a spdt switch, like on the redbear labs IoTpHAT https://redbear.cc/product/ Although I'm not sure about any that would fit directly instead of the 0 ohm resistor I'm not sure if longer traces might have a negative effect.

The zero-ohm resistor is common in mass-produced boards where machines do 99% of the assembly. in through-hole assembly we would have used a simple jumper.

Excellent Tutorial, and nice photos.

Nice mod. I have a question. Do you think that the bluetooth module also uses this antenna and thus would get its range increased as well?

I think the bluetooth module must use the same antenna and so its range would also increase.

Thanks for excellent tutorial. You're not breaking against any regulations if you for example create a packet sniffer. Then there is no Tx so you can add a 30dBi antenna if you want. For transmission, I also doubt the radio chipset that sits there at the moment gives 20dBm. It's very common in for example phones that Wi-Fi gives maximum 14-17dBm in Tx mode (compare with up to 2W for cellular radios, but those use power adjustments while the Wi-Fi Tx power is on a constant level). Question: is it possible to squeeze an SMA connector on to that pad rather than a UFL? Don't like UFLs. They come off easily.

I dont think a sma would fit on the pad, but you could use a short ufl to sma socket lead and then glue the wire to the board to stop the ufl connector from coming away.

This really is a great idea and should be a factory-feature. I am going to be mounting my Pi Zero in a fully sealed aluminum enclosure, and I need a coax connector at the outside for an antenna. This article was VERY useful.

Interesting to see that external antenna does not works "far much better" than the original.
When you tested the external antenna, it was like on the pictures, not up/down like a normal antenna? That may explain small difference?

Since the Pi-ZW is certified as an FCC Part 15 device (https://fccid.io/2ABCB-RPI0W), any antenna must be an integral part of the device and not user-changeable.

From the Part 15 regulations (47 CFR 15.203 Antenna Requirements)
"... each Part 15 transmitter must be designed to ensure that no type of antenna can be used with it other than the one used to demonstrate compliance with the technical standards. This means that Part 15 transmitters must have permanently attached antennas, or detachable antennas with unique connectors. A "unique connector" is one that is not of a standard type found in electronic supply stores."

Technically- it is an FCC violation to modify the antenna. In the real world, nobody knows if you peed in the pool.

Hi I have a small question I lost the resistance by desoldering. I wanted to know the value of the resistance to be able to replace it

It is a zero ohm resistor to link across the pads.

@Steve Mann

But, if you're a licensed amateur radio operator, you have license in the 2.4ghz band, and wifi transmitting is then covered under Part 90 rather than Part 15.
Fun to know.

What about doing in some oter way?....

For not so "precise" soldering:

Removing the "dummy load" resistor and coils near the trapezoidal area, then "bridge" the two connections (pcb antenna and connector for the external).

I think it will make thing easier for thos without microscope. ;)

Since it's just a 0 ohm resistor, do you even really need it? You could just remove it and put a piece of wire to patch over.. Or even leave it and add the wire in as well, I mean, cause is there any harm in having both antenna's attached at the same time? lol

OkinSama, If the resistor was left in place giving two antennas it would cause an rf impedance mismatch on the driver circuit which could damage the WiFi chip.

I found your article by accident... Had a zero w idling around here and had the opportunity to get all parts for 8€ locally...

I hammered everything together with a 50€ el'cheapo soldering station and a 10x Watchmakers magnifying glass.
??
All in all, took me less than 15 minutes and my range doubled with a Tp-Link 29cm 8db antenna.

Thanks for the idea :)

My interest is not in extending range, but in being able to use a metal industrial case with an external antenna. Is there a solution for this that doesn't violate FCC rules? Thanks!

Darren, I think adding the external antenna would techincally break the FCC rules but unless you are selling the upgraded boards and cases I dont think you would have any issues.

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