8 ms·

Raspberry Pi Zero 2 W external antenna mod

111 points by finex 5y ago

fredoralive 5y ago
It's always a bit disappointing when you have one of these pages and it's just "the designers left a footprint to fit the part" and no bodging required. Still, seems a useful bit of forethought from the designers.
- londons_explore 5y ago
  It's pretty rare designers don't leave a footprint for antenna connectors. The footprint is pretty small, and makes debugging and testing of the software stack far easier since you can plug the connector into other hardware which simulates other wireless devices, without requiring an expensive and hard to use RF chamber.
  - buescher 5y ago
    They use it in their part 15 compliance testing. Conducted power output is a standard test. The alternative is bodging a connector onto the board.
- PragmaticPulp 5y ago
  The number of people doing this mod is probably less than 1 in 10,000 to 1 in 100,000 units shipped. If the connector cost was $0.25, that could mean the Raspberry Pi foundation was spending $2,500 to $25,000 for every one person doing this mod. It would be a very poor financial decision. Including the footprint is free, though.
  - soneil 5y ago
    I believe not including the connector factors into their FCC certification
LaputanMachine 5y ago
> You'll be expected to never turn on your Pi Zero without an antenna attached again, should your transmitter get fatally confused by the mismatch of hardware-defined impedance assumptions. Can the hardware really be damaged by using it without an antenna? I would not have expected that at all.
- betamaxthetape 5y ago
  Indeed it can - if the impedances are not matched correctly, the transmitted signals can end up being reflected back down the antenna, causing damage to the transmitter. The Wikipedia article on Standing Wave Ratios [1] has more on this topic. [1] https://en.wikipedia.org/wiki/Standing_wave_ratio https://en.wikipedia.org/wiki/Standing_wave_ratio
  - buescher 5y ago
    It can, but I’d be a little surprised if the zero w makes enough power to destroy its output without an antenna.
  - martin_a 5y ago
    > Indeed it can - if the impedances are not matched correctly, the transmitted signals can end up being reflected back down the antenna, causing damage to the transmitter. I think I've seen this once in a documentary where this blew up a whole ship and then many others, too. I think it was called Independence Day or sth. like that.
    - Crosseye_Jack 5y ago
      Wasn't that a computer virus?
      - martin_a 5y ago
        Nah, I was thinking about this: https://youtu.be/NyOTaHRBTXc?t=110 https://youtu.be/NyOTaHRBTXc?t=110
  - 5y ago
mschuster91 5y ago
Why does the person in the video cut off the PCB antenna with a dremel and short-cut the resistor pads, instead of simply taking the SMD resistor that is ~1cm left-bottom and connects the antenna trace to the PCB antenna?
- regularfry 5y ago
  That's explained in the comments on the original source. It turns out that the curved bit of trace is significant: if you leave it connected but unterminated it'll be resonant near the 5th harmonic of the wifi signal, which is bad. Microwave RF is hard.
  - regularfry 5y ago
    Oh, also it's a capacitor, not a resistor. I don't think that changes the explanation, though.
    - jacquesm 5y ago
      On the contrary, that makes all the difference: it's an LC circuit that is resonant at a frequency that you don't intend to amplify.
      - regularfry 5y ago
        It is, but if the proposal is to desolder the component from the board, does it matter which it was?
  - myself248 5y ago
    By the time you get to that high a harmonic, the signal is way, way, way down. I have to imagine these footprints, both the u.fl footprint and the 0402 footprint, were meant to be used during testing, and I can't imagine that their own testing also involved Dremeling off a trace. Removing the cap at the end of the curved stub is surely fine.
    - 5y ago
tpmx 5y ago
The original article is much better: https://www.briandorey.com/post/raspberry-pi-zero-2-w-external-antenna-mod https://www.briandorey.com/post/raspberry-pi-zero-2-w-extern...
- Tempest1981 5y ago
  Oh wow, much better. Looks like this shopping site just copied chunks of the Brian's article... hopefully with his permission.
  - wrycoder 5y ago
    Yeah, I loved the popup over popup right upon opening the page.
- martin_a 5y ago
  Maybe @dang can fix the link?
starklevnertz 5y ago
Raspberry Pi Zero is basically no longer available. Out of stock everywhere. With the chip shortage who knows how long till they’re generally available again.
- Crosseye_Jack 5y ago
  Dunno where in the world you are but there are still a few on sheves. https://coolcomponents.co.uk/products/raspberry-pi-zero-2-w https://coolcomponents.co.uk/products/raspberry-pi-zero-2-w still have a few but they are limiting sales to 1 per customer atm.
  - autofiend 5y ago
    Where I live they sell pretty quickly but they also get restocked quickly. Slightly more pent up demand, but nothing like a GPU. I bought one to set up some home automation.
    - Crosseye_Jack 5y ago
      Dunno what the performance of the Pi Zero 2 is compared to the Pi3 (iirc they have the same number of cores, but the Pi Zero 2 has less ram), but I happily run Home Assistant on a Pi3 even with a couple of DOODS detectors running on it processing camera feeds (however it takes about 500ms to process them iirc - its been a while since I set them up and I actually store the recordings of those cameras off the Pi). Have fun, its a rabbit hole, but a fun one :-) EDIT: Also if you are in the UK. Poundland have some Tuya/SmartLife compatable Wifi sockets for £5 a piece - https://www.poundland.co.uk/446890-ultrabrite-wifi-controlled-socket-plug/ https://www.poundland.co.uk/446890-ultrabrite-wifi-controlle... You can open them and reflash then with Tasmota but they are a pain to open. The EASY option is to stick with using Tuya/Smartlife and add Tuya/Smartlife to HA, just remember to remove the Smartlife skill from Alexa otherwise you can end up with dupicates and Alexa getting confused when you want to turn things on/off. ATM (imo) the "tuya old" intergration is better than the current offical tuya version (They changed things when updating it, which removed some compatibility but they said they would re add it at a later date, but duno if Tuya actually got round to it yet). Also if you do use Home Assisant, get into the habbit of reading the patch notes before updating, quiet often there will be breaking changes which mess up with your set up.
momenti 5y ago
The 1st-gen Zero had the same resonance cavity antenna on-board,[1][2] but it had a nicer design for the external antenna, namely a 0-Ohms(?) resistor that could be desoldered and resoldered at an angle (and be reverted if need be),[3] rather than crudely cutting the trace. [1] https://i.redd.it/fido28zdv1331.jpg https://i.redd.it/fido28zdv1331.jpg [2] https://www.embeddedcomputing.com/technology/analog-and-power/power-semiconductors-wireless-charging/a-lesson-in-wireless-engineering-from-the-raspberry-pi https://www.embeddedcomputing.com/technology/analog-and-powe... [3] https://www.briandorey.com/post/raspberry-pi-zero-w-external-antenna-mod https://www.briandorey.com/post/raspberry-pi-zero-w-external...
- itsbenweeks 5y ago
  I'm curious if you could desolder and use one of the resistors further down the trace to avoid having to scrape off the mask.
stere 5y ago
That's so cool! Should be one hell of a wireless router. Maybe it would even work on bonding multiple connections.
- DnDGrognard 5y ago
  Put it up a watertight enclosure Hook it up to a directional antenna and it would make a good PTP set up.
yjftsjthsd-h 5y ago
Okay, technically cool, but is it legal? Seems like something the FCC (or local equivalent) would have an opinion about
- axiak 5y ago
  It's been a while since I've read FCC rules, but as far as I know they usually regulate power output, not antenna design.
  - buescher 5y ago
    They regulate effective radiated power (except for the AM broadcast band), which is a function of both conducted power output and antenna design. Any part 15 stuff like WiFi that has replaceable antennas will typically be certified for use with specific antennas. (there are plenty other rules too) So this hack is not FCC certified (since it isn't what was tested for the zero W 2 certification) and may or may not be compliant.
alias_neo 5y ago
My understanding, from experience of finding similar footprints on other hardware, was that this footprint is there for testing in the factory and not actually intended to be a u.FL footprint for an external antenna. I think the first time I saw it was on a GL.iNet mini router which I wanted to add an external antenna to. It's possible, but you have to cut the trace to the on-board antenna. Can anyone confirm or deny this?
ComputerGuru 5y ago
This is just a supplier generating traffic to their website. The actual post is here and has the real details: https://www.briandorey.com/post/raspberry-pi-zero-2-w-external-antenna-mod https://www.briandorey.com/post/raspberry-pi-zero-2-w-extern...
- tyingq 5y ago
  "to fit a zero ohm resistor (0201 size 0.6mm x 0.3mm)" I know what they mean here, but I had to re-read "zero ohm resistor" a few times.
  - azalemeth 5y ago
    0 Ω links are commonly used on SMT boards as bridges, to avoid having to either have another layer or make routing easier when you have relatively hard constraints (e.g. ground planes behind antennas). The added marginal cost of a 0 Ω 0201 SMT link is basically $0 to about 3 s.f.. The added cost of another layer in the board is decidedly nonzero. Yes, they made me blink the first time I encountered them too...

111 points by finex 5y ago

It's always a bit disappointing when you have one of these pages and it's just "the designers left a footprint to fit the part" and no bodging required. Still, seems a useful bit of forethought from the designers.

londons_explore 5y ago
It's pretty rare designers don't leave a footprint for antenna connectors. The footprint is pretty small, and makes debugging and testing of the software stack far easier since you can plug the connector into other hardware which simulates other wireless devices, without requiring an expensive and hard to use RF chamber.
- buescher 5y ago
  They use it in their part 15 compliance testing. Conducted power output is a standard test. The alternative is bodging a connector onto the board.
PragmaticPulp 5y ago
The number of people doing this mod is probably less than 1 in 10,000 to 1 in 100,000 units shipped. If the connector cost was $0.25, that could mean the Raspberry Pi foundation was spending $2,500 to $25,000 for every one person doing this mod. It would be a very poor financial decision. Including the footprint is free, though.
- soneil 5y ago
  I believe not including the connector factors into their FCC certification

LaputanMachine 5y ago

> You'll be expected to never turn on your Pi Zero without an antenna attached again, should your transmitter get fatally confused by the mismatch of hardware-defined impedance assumptions. Can the hardware really be damaged by using it without an antenna? I would not have expected that at all.

betamaxthetape 5y ago
Indeed it can - if the impedances are not matched correctly, the transmitted signals can end up being reflected back down the antenna, causing damage to the transmitter. The Wikipedia article on Standing Wave Ratios [1] has more on this topic. [1] https://en.wikipedia.org/wiki/Standing_wave_ratio https://en.wikipedia.org/wiki/Standing_wave_ratio
- buescher 5y ago
  It can, but I’d be a little surprised if the zero w makes enough power to destroy its output without an antenna.
- martin_a 5y ago
  > Indeed it can - if the impedances are not matched correctly, the transmitted signals can end up being reflected back down the antenna, causing damage to the transmitter. I think I've seen this once in a documentary where this blew up a whole ship and then many others, too. I think it was called Independence Day or sth. like that.
  - Crosseye_Jack 5y ago
    Wasn't that a computer virus?
    - martin_a 5y ago
      Nah, I was thinking about this: https://youtu.be/NyOTaHRBTXc?t=110 https://youtu.be/NyOTaHRBTXc?t=110
- 5y ago

mschuster91 5y ago

Why does the person in the video cut off the PCB antenna with a dremel and short-cut the resistor pads, instead of simply taking the SMD resistor that is ~1cm left-bottom and connects the antenna trace to the PCB antenna?

regularfry 5y ago
That's explained in the comments on the original source. It turns out that the curved bit of trace is significant: if you leave it connected but unterminated it'll be resonant near the 5th harmonic of the wifi signal, which is bad. Microwave RF is hard.
- regularfry 5y ago
  Oh, also it's a capacitor, not a resistor. I don't think that changes the explanation, though.
  - jacquesm 5y ago
    On the contrary, that makes all the difference: it's an LC circuit that is resonant at a frequency that you don't intend to amplify.
    - regularfry 5y ago
      It is, but if the proposal is to desolder the component from the board, does it matter which it was?
- myself248 5y ago
  By the time you get to that high a harmonic, the signal is way, way, way down. I have to imagine these footprints, both the u.fl footprint and the 0402 footprint, were meant to be used during testing, and I can't imagine that their own testing also involved Dremeling off a trace. Removing the cap at the end of the curved stub is surely fine.
  - 5y ago

tpmx 5y ago

The original article is much better: https://www.briandorey.com/post/raspberry-pi-zero-2-w-external-antenna-mod https://www.briandorey.com/post/raspberry-pi-zero-2-w-extern...

Tempest1981 5y ago
Oh wow, much better. Looks like this shopping site just copied chunks of the Brian's article... hopefully with his permission.
- wrycoder 5y ago
  Yeah, I loved the popup over popup right upon opening the page.
martin_a 5y ago
Maybe @dang can fix the link?

starklevnertz 5y ago

Raspberry Pi Zero is basically no longer available. Out of stock everywhere. With the chip shortage who knows how long till they’re generally available again.

Crosseye_Jack 5y ago
Dunno where in the world you are but there are still a few on sheves. https://coolcomponents.co.uk/products/raspberry-pi-zero-2-w https://coolcomponents.co.uk/products/raspberry-pi-zero-2-w still have a few but they are limiting sales to 1 per customer atm.
- autofiend 5y ago
  Where I live they sell pretty quickly but they also get restocked quickly. Slightly more pent up demand, but nothing like a GPU. I bought one to set up some home automation.
  - Crosseye_Jack 5y ago
    Dunno what the performance of the Pi Zero 2 is compared to the Pi3 (iirc they have the same number of cores, but the Pi Zero 2 has less ram), but I happily run Home Assistant on a Pi3 even with a couple of DOODS detectors running on it processing camera feeds (however it takes about 500ms to process them iirc - its been a while since I set them up and I actually store the recordings of those cameras off the Pi). Have fun, its a rabbit hole, but a fun one :-) EDIT: Also if you are in the UK. Poundland have some Tuya/SmartLife compatable Wifi sockets for £5 a piece - https://www.poundland.co.uk/446890-ultrabrite-wifi-controlled-socket-plug/ https://www.poundland.co.uk/446890-ultrabrite-wifi-controlle... You can open them and reflash then with Tasmota but they are a pain to open. The EASY option is to stick with using Tuya/Smartlife and add Tuya/Smartlife to HA, just remember to remove the Smartlife skill from Alexa otherwise you can end up with dupicates and Alexa getting confused when you want to turn things on/off. ATM (imo) the "tuya old" intergration is better than the current offical tuya version (They changed things when updating it, which removed some compatibility but they said they would re add it at a later date, but duno if Tuya actually got round to it yet). Also if you do use Home Assisant, get into the habbit of reading the patch notes before updating, quiet often there will be breaking changes which mess up with your set up.

momenti 5y ago

The 1st-gen Zero had the same resonance cavity antenna on-board,[1][2] but it had a nicer design for the external antenna, namely a 0-Ohms(?) resistor that could be desoldered and resoldered at an angle (and be reverted if need be),[3] rather than crudely cutting the trace. [1] https://i.redd.it/fido28zdv1331.jpg https://i.redd.it/fido28zdv1331.jpg [2] https://www.embeddedcomputing.com/technology/analog-and-power/power-semiconductors-wireless-charging/a-lesson-in-wireless-engineering-from-the-raspberry-pi https://www.embeddedcomputing.com/technology/analog-and-powe... [3] https://www.briandorey.com/post/raspberry-pi-zero-w-external-antenna-mod https://www.briandorey.com/post/raspberry-pi-zero-w-external...

itsbenweeks 5y ago
I'm curious if you could desolder and use one of the resistors further down the trace to avoid having to scrape off the mask.

stere 5y ago

That's so cool! Should be one hell of a wireless router. Maybe it would even work on bonding multiple connections.

DnDGrognard 5y ago
Put it up a watertight enclosure Hook it up to a directional antenna and it would make a good PTP set up.

yjftsjthsd-h 5y ago

Okay, technically cool, but is it legal? Seems like something the FCC (or local equivalent) would have an opinion about

axiak 5y ago
It's been a while since I've read FCC rules, but as far as I know they usually regulate power output, not antenna design.
- buescher 5y ago
  They regulate effective radiated power (except for the AM broadcast band), which is a function of both conducted power output and antenna design. Any part 15 stuff like WiFi that has replaceable antennas will typically be certified for use with specific antennas. (there are plenty other rules too) So this hack is not FCC certified (since it isn't what was tested for the zero W 2 certification) and may or may not be compliant.

alias_neo 5y ago

My understanding, from experience of finding similar footprints on other hardware, was that this footprint is there for testing in the factory and not actually intended to be a u.FL footprint for an external antenna. I think the first time I saw it was on a GL.iNet mini router which I wanted to add an external antenna to. It's possible, but you have to cut the trace to the on-board antenna. Can anyone confirm or deny this?

ComputerGuru 5y ago

This is just a supplier generating traffic to their website. The actual post is here and has the real details: https://www.briandorey.com/post/raspberry-pi-zero-2-w-external-antenna-mod https://www.briandorey.com/post/raspberry-pi-zero-2-w-extern...

tyingq 5y ago
"to fit a zero ohm resistor (0201 size 0.6mm x 0.3mm)" I know what they mean here, but I had to re-read "zero ohm resistor" a few times.
- azalemeth 5y ago
  0 Ω links are commonly used on SMT boards as bridges, to avoid having to either have another layer or make routing easier when you have relatively hard constraints (e.g. ground planes behind antennas). The added marginal cost of a 0 Ω 0201 SMT link is basically $0 to about 3 s.f.. The added cost of another layer in the board is decidedly nonzero. Yes, they made me blink the first time I encountered them too...