Phase Centre of WiFi dongle


John E. Beech
 

Hi All,
Anyone any idea od where the phase centre of the antenna inside a wiFi Dongle might be? Specifically a D-link
DWL-G122 H/W. It is 60 mm high excluding the USB connector.

I'd like to be in or near the ball bark with my mounting, as I don't have much adjustment once it is fitted to my dish f/D
ratio about 0.3. I'm trying to extend the range for a point-to-point connection.

de John G8SEQ


Glyn M0XGT
 

It's usually at the far end opposite the USB connector (along with a u.fl test connector that you can hack). 
What sort of link distance are you aiming for?

Glyn M0XGT 


Peter Burgess
 

Hi John

A google search for D-link DWL-G122 H/W pcb brought up an image of a dissasmbled unit.
It looks like it uses a small ceramic chip antenna under the Act LED label.

Peter
G4BCH


John E. Beech
 

Tnx fer that Peter,
Is that white ceramic thing really an antenna for 2.45 GHz. I've never seen one like that &
wouldn't have recognised it as an antenna. Or is it a matching device or phase shifting device for a track on the
other side of the PCB that acts as an antenna. I'm thinking circular / mixed polarization. There is some symmetry to
the board which suggests there may be two antennas at right angles, if you look at the bottom LH corner of the
board.

de John G8SEQ

-------Original Message-------
From: Peter Burgess via groups.io <g4bch=yahoo.com@groups.io>
To: ukmicrowaves@groups.io <ukmicrowaves@groups.io>
Subject: Re: [UKMicrowaves] Phase Centre of WiFi dongle
Sent: Mar 07 '21 18:09

Hi John

A google search for D-link DWL-G122 H/W pcb brought up an image of a
dissasmbled unit.

http://studycasini.dx.am/d-link-dwl-g700ap-drivers-for-mac.html image
near the bottom of the page.

It looks like it uses a small ceramic chip antenna under the Act LED
label.

Peter
G4BCH


John E. Beech
 

Tnx Glynn,
I did do some tests a few years ago which showed some promise. I used a Sky/Amstrad elliptical dish (
designed for 11 GHz, so reduced gain at 2.45 GHz about 20 dB) at one end with a helical feed antenna and about
10 ft of RG58 with an SMA connector on one end to connect to the Wifi card in a desktop PC. The other end of
the link had a
60 cm diam Grampian outside broadcast microphone dish ( also about 20 dB, which I had previously used on 3 cm
WBFM) with the dongle at/near the focus. It worked over the length of my garden - hardly surprising as the distance
was only 130 feet! The "normal" wifi set-up dropped out at that distance.
I then tried it at a range of about 1 km ie between my QTH & Coventry ARS QTH with mixed results. The
path should be line of sight, across a valley, but it is obstructed. The only place I could detect it was 50 yards up the
drive (inconvenient) from the club house ( church hall). At the time I chose "middle for diddle" as far as dongle/dish
focus went.
However, since then one of the obstructions to wit a 120 ft tall Lombardy Poplar tree at the bottom of my
garden has gone - blown down in a gale and sawn up for firewood. So I thought I might try again, but this time
optimising the system a bit better. And perhaps I might get it to work via a reflectin path as there are a number of
high rise buildings dotted about the area.

de John G8SEQ

-------Original Message-------
From: Glyn M0XGT <glyn.thomas512@gmail.com>
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] Phase Centre of WiFi dongle
Sent: Mar 07 '21 17:15

It's usually at the far end opposite the USB connector (along with a
u.fl test connector that you can hack).
What sort of link distance are you aiming for?

Glyn M0XGT


Glyn M0XGT
 

I think it’s always going to be slightly tricky relying on the internal antenna in the dongle – better to either hack the board and connect via the test connector or use a device that has external antenna connectors. 
 
The solution I like is a Ubiquiti Bullet M5, or dual-chain Rocket M5, with external N-type or SMA (after RP-SMA adaptors) connectors and an Ethernet connection to a 24V POE switch or POE injector plus 24V DC-DC converter and LiPo. This lets you put the access point at the top of a mast with data and power run over a long outdoor Ethernet cable, and it leaves you with just a short coax run to the antenna ports. I get the ubiquity kit on eBay, new from Latvia or used from UK/EU.
 
I have a collection of different antennas depending on the task: 6 dBi or 8 dBi omnis for UAV ground-to-air links or general area coverage, a pair of 18 dBi patches for moderate distance, and a pair of 28 dBi dual-polarised dishes for much long point-to-point links. For short range links you can push the data-link channel bandwidth right up (300 Mb/s with 40 MHz channels, dual-chain) or dial it down to increase the range. 
 
Glyn M0XGT  
 


Murray Niman
 


Plenty of small ceramic antennas around...
Look on here and you will see similar:-

https://uk.farnell.com/c/passive-components/antennas-single-band-chip

Their physical size vs freespace wavelength may not be uber-efficient though, but for short range WiFi or bluetooth it doesnt matter much

  Murray


John E. Beech
 

Very interesting Murray. Shows how much I'm out of touch with modern electronics. However, after googling how they
work, it seems the associated ground plane is doing a lot of the radiating & in a dongle the g-plane is probably acting
more like a patch antenna.
I might buy a few and try them as a dish feed.

de John G8SEQ

-------Original Message-------
From: Murray Niman <g6jyb@microwavers.org>
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] Phase Centre of WiFi dongle
Sent: Mar 08 '21 06:50

Plenty of small ceramic antennas around...
Look on here and you will see similar:-

https://uk.farnell.com/c/passive-components/antennas-single-band-chip

Their physical size vs freespace wavelength may not be uber-efficient
though, but for short range WiFi or bluetooth it doesnt matter much

Murray