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abelectronicsuk
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External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 2:05 pm

I have modified the new Raspberry Pi Zero W to add a U.FL antenna connector to use an external WiFi aerial with the new Pi and added more photos and the parts required to my blog at http://www.briandorey.com/post/Raspberr ... ntenna-mod

Image

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mahjongg
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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 2:59 pm

Great! I see from your blog that it does really work!

Note that by replacing the certified antenna with another uncertified antenna you have invalidated FCC certification, but as that is true for any radio device with a replaceable antenna it not a big deal, as long as you do not blame the RPF when they come knocking on your door. LOL :lol: :mrgreen: :ugeek:

Its really great, and I see that you used the tip I mentioned in the blog to turn the zero ohms reistor 90 degrees, unless of course you thought of that yourself.

I'm very happy this is possible, and isn't too difficult to do!

now see if an antenna for the FM radio function in the chip is also possible. :mrgreen:

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bensimmo
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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 3:40 pm

What happens if you have them both connected up ?

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abelectronicsuk
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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 4:00 pm

bensimmo wrote:What happens if you have them both connected up ?
The resistor link changes the port/antenna used so this mod disconnects the PCB antenna. if both are connected there would be a RF mismatch between the antennas which could damage the RF stages in the chip.

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abelectronicsuk
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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 4:48 pm

mahjongg wrote: Its really great, and I see that you used the tip I mentioned in the blog to turn the zero ohms reistor 90 degrees, unless of course you thought of that yourself.
I didnt see your post about the resistor, it wasnt the easiest component to move, not sure what size it is but with the 0.5mm soldering iron tips it still was tricky to move!

The photo below shows the new modified board fitted to the barcode scanner pcb which has the adafruit touchscreen fitted on top so the onboard antenna would have been shielded by both PCB's.
Image

alphanumeric
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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 6:28 pm

Working with SMT parts is always fun with just regular soldering iron. :| I may try that myself. When I finally get my hands on Zero W.

Heater
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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 7:19 pm

Given that zero ohm resistor is just a jumper would it not be easier to just leave it where it is, make a new bridge with a blob of solder and scratch a gap in the PCB trace in the direction you don't want to go?

Saves all that messing trying move the "resistor".

Unless you expect to want to undo the mod of course.
Memory in C++ is a leaky abstraction .

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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 7:32 pm

abelectronicsuk wrote:....... it wasnt the easiest component to move, not sure what size it is but with the 0.5mm soldering iron tips it still was tricky to move!....
I don't have a RPi 0W to verify this but the resistor is likely a 0 Ohm resistor which can be replaced by a wire or in a pinch a solder bridge.
Unless specified otherwise my response is based on the latest and fully updated RPiOS Buster w/ Desktop OS.

Heater
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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 7:37 pm

That is what I just said.

If you just bridge it with a solder blob the old antenna is still connected. Hence my suggestion to scrape the PCB trace away.
Memory in C++ is a leaky abstraction .

alphanumeric
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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 7:41 pm

Assuming it is a resistor and not an inductor.
From the link
"On the Raspberry Pi PCB there is a component which appears to be a zero ohm resistor".

An inductor would measure zero of near zero ohms. It can be hard to tell sometimes exactly what something is when dealing with SMT components. If it is a resistor, you could just carefully cut it in half, with wire cutters or a dremel. Then unsolder each end one at a time. Then just solder in a wire jumper the other way.

Somebody from the RPF, that has access to a schematic could verify exactly what it is.

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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 7:53 pm

If you're removing the resistor completely why not connect a SPDT switch (or even header pins with a jumper) so you can choose between external or internal WiFi antenna.
Note: Any requirement to use a crystal ball or mind reading will result in me ignoring your question.

Criticising any questions is banned on this forum.

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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 7:59 pm

DougieLawson wrote:If you're removing the resistor completely why not connect a SPDT switch (or even header pins with a jumper) so you can choose between external or internal WiFi antenna.
That's fine for DC voltages etc. It doesn't always work so good for RF though. ;) Stray capacitance or inductance for example.

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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 8:11 pm

alphanumeric wrote:
DougieLawson wrote:If you're removing the resistor completely why not connect a SPDT switch (or even header pins with a jumper) so you can choose between external or internal WiFi antenna.
That's fine for DC voltages etc. It doesn't always work so good for RF though. ;) Stray capacitance or inductance for example.
Ah, I've never worked with RF beyond the capacitor, coil and crystal on a MW AM crystal set in the 1970s.
Note: Any requirement to use a crystal ball or mind reading will result in me ignoring your question.

Criticising any questions is banned on this forum.

Any DMs sent on Twitter will be answered next month.
All non-medical doctors are on my foes list.

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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 8:17 pm

It would have to be a very small SPDT switch. Like the size of that zero ohm resistor :)
Memory in C++ is a leaky abstraction .

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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 8:21 pm

DougieLawson wrote:
alphanumeric wrote:
DougieLawson wrote:If you're removing the resistor completely why not connect a SPDT switch (or even header pins with a jumper) so you can choose between external or internal WiFi antenna.
That's fine for DC voltages etc. It doesn't always work so good for RF though. ;) Stray capacitance or inductance for example.
Ah, I've never worked with RF beyond the capacitor, coil and crystal on a MW AM crystal set in the 1970s.
I'm a retired electronic technician. I worked in the installation and maintenance or electronic equipment used is civil aviation here in Canada. Basically all the ground based equipment an aircraft uses for takeoff, landing, navigation and communication. Instrument Landing Systems, RADAR, Navigation Beacons, VHF, UHF, MF, HF, etc. And the computers used for maintenance and control. A jumper pin, like what is used on the GPIO, will be an antenna at the right frequency. ;)

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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 8:26 pm

Heater wrote:That is what I just said.

If you just bridge it with a solder blob the old antenna is still connected. Hence my suggestion to scrape the PCB trace away.
Your post was not there when I clicked reply.

There is no need to scrape any trace away. Scrape what trace?

Bridging with solder or wire would have to be done by first removing the zero Ohm and then shorting across the 2 pads as shown in the photo in the OP........ Diagonally from the left pad to the lower pad leading to the external antenna connector. The pad on the right leads to the on board PCB trace antenna which would be disconnected when the 0 Ohm is removed.
Unless specified otherwise my response is based on the latest and fully updated RPiOS Buster w/ Desktop OS.

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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 8:27 pm

Heater wrote:It would have to be a very small SPDT switch. Like the size of that zero ohm resistor :)
The resistor is a 0201 size so need a switch 0.6mm x 0.3mm :)

At 2.4GHz a 1/4 wave antenna is only 31.25mm so adding a set of jumpers the size of a GPIO header would be getting close to the resonant frequency of the Wifi / bluetooth transmitters.

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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 8:33 pm

abelectronicsuk wrote:
Heater wrote:It would have to be a very small SPDT switch. Like the size of that zero ohm resistor :)
The resistor is a 0201 size so need a switch 0.6mm x 0.3mm :)

At 2.4GHz a 1/4 wave antenna is only 31.25mm so adding a set of jumpers the size of a GPIO header would be getting close to the resonant frequency of the Wifi / bluetooth transmitters.
Exactly, and set up standing waves etc and mess things up royally. In simple terms, it could detune the circuit to a point where it doesn't work at all. It would be like connecting the wrong antenna. AKA coat hanger, lol.

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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 8:53 pm

klricks,
There is no need to scrape any trace away. Scrape what trace?
You are not as lazy as me.

I would leave the zero ohm resistor in place. Make a solder bridge from the resistor to the pad to the south. Then slice the track to the right with an exacto knife. Job done.
Memory in C++ is a leaky abstraction .

digger72
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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 9:25 pm

Any idea on relative performance gain with external antenna.

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CarlRJ
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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 9:37 pm

digger72 wrote:Any idea on relative performance gain with external antenna.
If you follow the link in the first post, he gives a nice table comparing signal strength between the internal and external antennas.

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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 10:03 pm

Heater wrote:klricks,
There is no need to scrape any trace away. Scrape what trace?
You are not as lazy as me.

I would leave the zero ohm resistor in place. Make a solder bridge from the resistor to the pad to the south. Then slice the track to the right with an exacto knife. Job done.
If you leave the resistor in place and also use an external antenna it would half the impedance to the RF section which will damage the RF stages.

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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 10:07 pm

If I leave the resistor in place and short the route to the new antenna connection with a solder blob, I can then cut the trace to the on board antenna with an exacto knife. Job done. No worries with half impedance, etc.
Memory in C++ is a leaky abstraction .

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solar3000
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Re: External Antenna connector for the Pi Zero W

Sat Mar 04, 2017 10:40 pm

mahjongg wrote:Great! I see from your blog that it does really work!

Note that by replacing the certified antenna with another uncertified antenna you have invalidated FCC certification, but as that is true for any radio device with a replaceable antenna it not a big deal, as long as you do not blame the RPF when they come knocking on your door. LOL :lol: :mrgreen: :ugeek:

Its really great, and I see that you used the tip I mentioned in the blog to turn the zero ohms reistor 90 degrees, unless of course you thought of that yourself.

I'm very happy this is possible, and isn't too difficult to do!

now see if an antenna for the FM radio function in the chip is also possible. :mrgreen:


Nonono! Don't LOL! This actually happened:
https://yro.slashdot.org/story/00/01/04 ... ow-by-blow
Antikythera

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rpdom
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Re: External Antenna connector for the Pi Zero W

Sun Mar 05, 2017 12:16 am

solar3000 wrote:
mahjongg wrote:Great! I see from your blog that it does really work!

Note that by replacing the certified antenna with another uncertified antenna you have invalidated FCC certification, but as that is true for any radio device with a replaceable antenna it not a big deal, as long as you do not blame the RPF when they come knocking on your door. LOL :lol: :mrgreen: :ugeek:

Its really great, and I see that you used the tip I mentioned in the blog to turn the zero ohms reistor 90 degrees, unless of course you thought of that yourself.

I'm very happy this is possible, and isn't too difficult to do!

now see if an antenna for the FM radio function in the chip is also possible. :mrgreen:


Nonono! Don't LOL! This actually happened:
https://yro.slashdot.org/story/00/01/04 ... ow-by-blow
That story is about an FM transmitter.

The chip on the Pi has a perfectly legal FM receiver
(but the antenna pin isn't connected to anything, so it can't be used)

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