Increase and Extend the Range of a USB Bluetooth Dongle!

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Intro: Increase and Extend the Range of a USB Bluetooth Dongle!

This modification is something I came up with after struggling to get a reasonable range from my Nokia N82 to my computer in another room.
The victim was a $8 USB Bluetooth dongle, with a usable range of about 10 metres (less through walls).
Being a radio ham, I am familiar with antennas, and know how critical it is to get the CORRECT antenna length, if your signal is going to be efficient.
I was surprised to find other 'range extender' mods on the net, which did not mention this important fact! (One site had someone who had attached a "foot long piece of wire" onto his USB dongle and was wondering why it didn't work very well!!!)
There is a recognised formula for calculating antenna length/frequency, which is (without going into detail) 300/frequency - i.e. 300/150(MHz) will give you 2 metres.
As Bluetooth devices work at frequencies of around 2450MHz, the formula will give you an antenna length of +/- 12cm.
This figure then has to be divided by 4 to give us a quarter wave antenna, which will be 30mm in length - THIS LENGTH IS CRITICAL!!!
25mm or 35mm will just make it less efficient (Lower range).
Your old CB antenna WILL NOT WORK!
So - if you are happy to try something (at your own risk), and want to get a significant increase in usable range for you dongle, go to the next step, but remember, the end result doesn't look pretty, but performs brilliantly!

Step 1: Opening Up the USB Bluetooth Device

To get started, we obviously have to get inside the dongle.
The picture shows the dongle with the 'antenna' on the side removed.
Don't worry, this antenna is just a plastic dummy, and performs no function at all!
The plastic case then has to be prised open, using either a flat blade screwdriver, or a blunt knife.
There are no screws.

Step 2: Inside the Bluetooth Dongle

OK, so now we're inside, and you should be looking at a small PCB (printed circuit board).
Having second thoughts now?
If you aren't confident with a soldering iron, simply pop everything back together again, and forget this mod.
If you are ok to continue (a small glass of whiskey will help!), then we'll move to the next stage.
On the side of the PCB with the 2 chips and a 13MHz crystal, you will see a hook-shaped silver line at the top of the board (I've marked this in YELLOW on the picture).
This is the antenna which you're using at the moment.
Now you can see why the range is somewhat limited!!
Ok, bite the bullet, because this has got to come out, and you're gonna remove it.
It is easier than you think, all you have to do is find a sharp utility/hobby knife, and simply SCRAPE IT OFF THE PCB.
Be very careful to scrape towards the edges of the PCB to avoid damaging the other smd components on the board.

***VERY IMPORTANT***
leave enough of the old antenna on the board to give you something to solder you new antenna onto.
I've marked the STOP area in RED on the pic.
DO NOT remove all of the old antenna (leave about 3-5mm)

Step 3: No Going Back Now!!

Right - The old antenna is now removed. The Yellow shows where it was, and now you should have a small left-over piece of the old antenna to give you something to attach (solder) your new antenna onto.
For the new antenna, I used a 30mm (CRITICAL!!!) piece of rigid copper wire (earth wire etc), which gives a better bandwidth, but is also liable to pull the old antenna track away from the PCB if soldered directly onto the track.
For this reason, I made a small hole in the PCB, using a small watchmakers' screwdriver (you can use a dremmel or 1mm drill bit).
Whatever method you use, make sure you support the PCB on a firm surface, to avoid stressing the board while you're making the hole.
The antenna is then threaded through the PCB from the other side.
Now it gets tricky, because you cannot hold the wire while you're soldering it to the track (it's too hot), so you need to find a way to support the board while you're soldering it.
Also remember to 'tin' the wire, before you solder it (it gives a better connection, and also solders quicker so you don't overheat the other components).


Step 4: New Antenna Is Now Attached.

When soldered in place, the antenna will now stand up vertically from the PCB, and is likely to come unattached, or break the old track (antenna), if you try to play with it (bend it straight etc), so LEAVE IT ALONE!
At this point, it would be wise to check that you have soldered it correctly, and have a good joint (connection).
HOLDING THE PCB BY THE EDGES, plug it into your USB socket (I use a short extension lead), and see if the LED lights up, and the device is recognised.
Don't touch the components while you're plugging it in, because you are almost certain to short something out, and totally wreck your new improved dongle.
You should already have a good idea what range you had before, and should now be able to see a significant increase in the operating range.
If you live in a well populated area, do a device scan to see if any phones etc are in range (you'll be surprised).
If all is ok, then you have another problem - how do I get it back into the plastic case?
I just used my still hot soldering iron to make a hole in the case for the antenna to poke through (I never said it was going to be pretty!!)
The hole should be in the plastic case which does NOT have writing on it, and is located level with the little plastic 'ledge' inside, where the PCB sits - on the opposite side to the hole for the 'dummy' antenna.
If you don't get the hole position quite right, DO NOT try to bend the antenna to fit through, make the hole bigger - you will avoid ripping the track up on the board.
As you can see from my picture, I got the position wrong, so just made a bigger hole. (ugly, but practical)

Step 5: That's All Folks.

With the case back in place, you're now the proud owner of probably the worlds ugliest looking USB Bluetooth dongle!
BUT on the positive side, you now have a Bluetooth dongle which will outperform anything for less than $50!
The range of mine is now a lot more than the 10-15 metres I got previously, with every room in the house being in range, and a 'line of sight' range in excess of 200 metres!
You could, of course, add a parabolic reflector (aluminium wok etc) to get ranges of more than 1 or 2km, but for practicality, I find the range more than adequate for my needs.
The same mod can also be applied to WiFi dongles, with similar increase in usable range, but I don't want to experiment with my $35 WiFi adaptor just at the moment (I'm poor!)
Also remember that Bluetooth operates a 'handshake' protocol, where it needs to recieve a signal, as well as transmit it, so if your phone has a naff bluetooth system, then don't expect to get much increase in range.
For sniffing out other devices in the neighbourhood though, you should find signals you couldn't detect before.
There are other antenna designs which you could also try (co-linear etc) which will improve things even more, but this design is a quick and cheap (free?) method to get the most from a cheap Bluetooth device.
Apologies for the terrible soldering in the picture, but I used a soldering gun for the job (yikes).
Any comments or questions can be sent to me at:
Nottslad89@yahoo.com
Good luck, and thanks for viewing.
Josh

3 People Made This Project!

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50 Discussions

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billb

9 years ago on Introduction

Please excuse my ignorance!!!!! If your antenna radiates 360° how is by turning it on its side will change its radiating properties. If vertical is 360° horizontal should also be 360° I'm clearly missing something. This is a SUPER COOL hack which I'd like to try but I'm missing something on the radiating pattern thing.

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Nottslad89billb

Reply 7 years ago on Introduction

I always say, 'only a question unasked, is dumb', so no worries.

Sorry for the late reply (2 years!), and no doubt you already know the answer.
Anyway, the 360 degree radiated pattern is formed around an antenna in a 'doughnut' configuration, and not like a sphere or ball surrounding the antenna.

Most of the signal is generated within this 'doughnut', with very little at the end of the antenna (the signal doesn't go up or down, only around).

If the antenna is horizontally polarized (laid down), the least amount of signal will be wherever you 'point' the antenna.

The signal degradation between a vertical and horizontal antenna is also a key factor, so if the TX antenna is vertical, then the RX antenna should also be vertical, or visa-versa...

Hope that cleared it up.

TTFN

NL89

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et1nusnbillb

Reply 9 years ago on Introduction

if one antenna is vert and the other is horz. you lose 3db (which is 1/2 the power) in which is called polerization mismatch. hopefully this is the answer you were looking for.

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Jean-BaptisteF

Question 6 weeks ago on Step 5

Hi,
Thanks for this guide.

Have you choosed to solder the antenna at 90deg from the PCB for any rf reason ? (PCB acting as ground plate ?)

Any reason you choosed to go quarter length and not half length or full length?

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BenjaminJ2

10 months ago

I recently bought a usb bluetooth dongle from ebay for $2 with free shipping for my dad, it only worked at a maximum of 10 feet, so I popped open the plastic cover and cut a three inch strip of tin foil and folded a tiny area at the end of the foil strip and wedged it under the printed circuit antenna and put the cover back together and now I can get the bluetooth speaker to work 200 feet direct line of sight, it even worked in my dads walk in closet on the other side of the house.

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idmadjBenjaminJ2

Reply 9 months ago

Pure genius. These dongles typically provide just enough range to be used on a laptop sitting a few cm from the peripheral. This mod makes it possible to have a strong signal even with the dongle plugged in the back of a PC sitting under a desk.

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ToddW71

10 months ago

Is there an optimal gauge size for the solid core copper wire antenna? Since the length of the wire is important and your calculations are precise to the mm, it would seem as though the wire gauge might also have an impact on performance. Thanks for the great post!

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ArgleB

1 year ago

Well whaddya know......it works! Amazing
what a little theory does. I just tried it on a cheapy $2 ebay dongle
that wouldn't get more than 1 metre range before the signal started to
break up and crackle. Now I've got about 5 metres! I did accidentally
pull up the remainder of the trace but my solder joint held. A little
dab of hot glue should hold it firm.

Also, don't bother picking
out all the existing antenna, simply make a wide cut in front of where
you will solder and the antenna is not connected anymore.

The original was ~45mm long

Thanks Josh

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fcampbell

8 years ago on Introduction

I appreciate the formula for calculating antenna length but I have a few questions.  You place a lot of emphasis on the correct length of the antenna but what about the conductor and wiring leading to the antenna?  If you solder a 30mm length of wire to a 4mm remnant of the old antenna, doesn't that leave you with a 34mm antenna?  And then, what if you folded the wire into a fractal shape.  Should a fractal antenna be made from the 30mm wire or should the final antenna be 30mm across?

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JoeF4fcampbell

Reply 1 year ago

The conductor between the antenna and the transmitter/receiver only matters in that it should be properly sized for the length required(antenna to transmitter/receiver) at the frequency which will be used.

In the sixty seconds I spent looking up "fractal antenna", I didn't find any made from wire.

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you can yes, just make sure the end result of the antenna is about 30mm in length, for the best results.

if the antenna on the board is about 15,, long, add a single wire that is about 15 mm long, and it should work just fine.

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MarcusR31

2 years ago

I have bought 6 bluetooth audio receivers and I would like to increase their range, although when I open them, they seem to have printed their antennas inbetween layers of the PCB. Is there a way to increase it anyhow? Best regards

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Peter2011MarcusR31

Reply 2 years ago

i have ones with a similar design, where i bought a small handful to try out different methods..

the one that works best so far, is to use old ribbon cable, make the length about 15mm and add it to the end of the antenna on the board(the red part, yoinked your image, hope you don't mind)

i got a good 10 meter range boost from it..

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wrecche

2 years ago

Nice work ! I am too jittery to solder efficiently, but the upside is the bluetooth dongle I have is a $2 gadget from china lol, so what is there to lose. :)

Actually, for the price and size (it's as big as a large dudes thumb nail) it's actually quite powerful already, it just doesn't play well with any interference.

Hoping something like this can resolve it, and if done properly, well it can't hurt aye !

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Mrinny

8 years ago on Introduction

I don't understand how this works.
With this bluetooth hack the usb dongle range has increased from say the default 10mts to either 20mts or above but other devices like mobile phones etc. will still have 10 mts range.
So how would the 2 devices communicate if the mobile phone is say 15mts away from the dongle?
That is only the pc dongle would be able to reach the mobile phone but not the other way around, isn't it?
Am I going wrong here?

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Nottslad89Mrinny

Reply 7 years ago on Introduction

The whole concept of this instructable is based on modifying the ANTENNA, leaving the actual power settings of the device unchanged.

Your phone/PDA etc does not need to be altered in any way, as the antenna on the dongle does all the work, enhancing both the transmitted and RECEIVED signals.

Bluetooth relies on a 2-way communication between devices, and is configured to work when a 'handshake' with a device has been established.

Since I wrote this article, there have been many advances in bluetooth technology and the modification of the new devices is easy, with a simple firmware hack/update changing power levels of the TX.
That still leaves you with the problem of receiving a low power device, and an antenna is the only solution, short of modding the device itself.

In any case, bluetooth was and still is only a SHORT RANGE communication medium, but I enjoy pushing the limits!

TTFN
NL89

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THX 1138Nottslad89

Reply 3 years ago on Introduction

Easy with simple firmware attacks? How do I go about that?

I've got a Kinivo BTD-400 and it's super compact and puts the pitiful antenna in the middle of a three-layer PCB! It's impossible to find a Bluetooth 3.0 or later dongle that doesn't use this compact format. The future is truly dystopian!

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madtaurus.z

3 years ago on Introduction

1. Is it posible to do it in a bluetooth headphones using a copper wire from a network cable?