[HN Gopher] Raspberry Pi Zero 2 W external antenna mod
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Raspberry Pi Zero 2 W external antenna mod
Author : finex
Score : 104 points
Date : 2021-12-15 10:30 UTC (12 hours ago)
(HTM) web link (shop.sb-components.co.uk)
(TXT) w3m dump (shop.sb-components.co.uk)
| fredoralive wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| I believe not including the connector factors into their FCC
| certification
| alias_neo wrote:
| 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?
| momenti wrote:
| 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
|
| [2] https://www.embeddedcomputing.com/technology/analog-and-
| powe...
|
| [3] https://www.briandorey.com/post/raspberry-pi-zero-w-
| external...
| itsbenweeks wrote:
| 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 wrote:
| That's so cool! Should be one hell of a wireless router. Maybe it
| would even work on bonding multiple connections.
| DnDGrognard wrote:
| Put it up a watertight enclosure Hook it up to a directional
| antenna and it would make a good PTP set up.
| ComputerGuru wrote:
| 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-extern...
| tyingq wrote:
| _" 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.
| LaputanMachine wrote:
| > 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.
| Fnoord wrote:
| AFAIK the same is true for any WLAN card with antennas, radio
| with antennas, HackRF, etc etc.
| londons_explore wrote:
| I know this is true for big multi-kilowatt power amplifiers.
|
| But are there any on-chip silicon amplifiers which can be
| damaged transmitting into a short or open circuit? Logic to
| detect that case and power off is trivial and should make the
| manufacturing process easier too (for one thing, rework of a
| dry solder joint on an antenna no longer requires the SoC to
| be replaced).
| betamaxthetape wrote:
| 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
| tzs wrote:
| This outstanding 1959 movie from Bell Labs demonstrates
| standing waves, impedance matching, and more in a very nice
| way using a couple of Shive wave machines, hosted by Dr.
| Shive himself [1].
|
| [1] https://www.youtube.com/watch?v=DovunOxlY1k
|
| [2] https://en.wikipedia.org/wiki/John_N._Shive
| martin_a wrote:
| > 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 wrote:
| Wasn't that a computer virus?
| martin_a wrote:
| Nah, I was thinking about this:
| https://youtu.be/NyOTaHRBTXc?t=110
| buescher wrote:
| It can, but I'd be a little surprised if the zero w makes
| enough power to destroy its output without an antenna.
| starklevnertz wrote:
| 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.
| bko wrote:
| It's not out of stock, you just have to buy it at the market
| price, which may be more than you're willing to pay.
|
| I just bought raspberry pi 4 on amazon through canakit. It came
| with a bunch of other stuff that was useful like sd card, case,
| cable, hdmi mini to hdmi converter, etc, so it really wasn't
| that bad.
|
| Here's the equivalent for rpi zero for $50
|
| https://smile.amazon.com/CanaKit-Raspberry-Wireless-Complete...
| Crosseye_Jack wrote:
| 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 still have a few but they are limiting sales to 1 per
| customer atm.
| autofiend wrote:
| 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 wrote:
| 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 PS5 a piece -
| 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.
| BenjiWiebe wrote:
| Some Tuya/SmartLife sockets can't be flashed with
| tasmota. I've got 2 that don't use Espressif SoC's.
| Crosseye_Jack wrote:
| Yeah I have one RGB light that uses a ThingsTurn module
| (which iirc is based on a w600) and I couldn't be arsed
| to swap out the module for a ESP.
|
| But I have 10 (8 in use, two on hand incase I ever want
| another lamp/secuirty light around the home, well atm the
| spares are in use for the christmas lights, but will go
| back into standby status after the lights come down.) of
| these ultrabight poundland sockets and all of them are
| ESP based. (though the ones I've recently added to my
| collection couldn't be flashed with tuyaconvert and
| needed some surgery, the last 2 in my collection I
| couldn't be arsed and just left them with the Tuya
| firmware and use the tuya API to control them, but thats
| my own lazyness not that they cna't be done.)
|
| For ceiling lights I use shellys so I could retain the
| use of the wall switch to control them.
| iicc wrote:
| >You can open them and reflash then with Tasmota but they
| are a pain to open.
|
| Not sure if you tried it, but depending on the age of the
| stock or the tardiness of the OEM in applying security
| patches, it may be possible to flash them without opening
| them first.
|
| https://github.com/ct-Open-Source/tuya-convert#procedure
| mschuster91 wrote:
| 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?
| nickcw wrote:
| A good question... The trace looks like it is enclosed in
| ground up to that moment so isn't intended to radiate until
| after the SMD resistor, so removing that resistor should be as
| good as cutting the trace.
|
| My hat's off to them though - that is some steady hand
| dremel/soldering work on something extremely tiny. Those little
| u.FL connectors are hard enough to mate with the connecting
| wire - I dread to think how difficult soldering them on by hand
| must be!
| regularfry wrote:
| 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.
| myself248 wrote:
| 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.
| regularfry wrote:
| Good point about the testing. I guess it's cheap and easy
| enough to try out, right?
| buescher wrote:
| If you trust your test setup for 17.4 GHz to be within a
| few dB of what you'd get at a certified test lab, sure.
|
| Yeah leaving the stub is bad practice because it _could_
| cause you trouble in FCC certification, not because it
| always will or even probably would. Let 's put it this
| way, if you _wanted_ to get enough energy into your fifth
| harmonic to be within 10 dB of what you were putting out
| on the fundamental by leaving a stub like that... you
| would tear your hair out for a good long while before
| giving up.
| myself248 wrote:
| Nothing about testing at those frequencies is cheap, and
| very little of it is easy, but it's certainly doable for
| someone who already has the lab.
| regularfry wrote:
| Oh, also it's a capacitor, not a resistor. I don't think that
| changes the explanation, though.
| jacquesm wrote:
| 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 wrote:
| It is, but if the proposal is to desolder the component
| from the board, does it matter which it was?
| [deleted]
| tpmx wrote:
| The original article is much better:
| https://www.briandorey.com/post/raspberry-pi-zero-2-w-extern...
| martin_a wrote:
| Maybe @dang can fix the link?
| Tempest1981 wrote:
| Oh wow, much better.
|
| Looks like this shopping site just copied chunks of the Brian's
| article... hopefully with his permission.
| wrycoder wrote:
| Yeah, I loved the popup over popup right upon opening the
| page.
| yjftsjthsd-h wrote:
| Okay, technically cool, but is it legal? Seems like something the
| FCC (or local equivalent) would have an opinion about
| axiak wrote:
| 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 wrote:
| 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.
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(page generated 2021-12-15 23:02 UTC)