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.

Comments

[billb]

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.

[et1nusn]

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.

[Nottslad89]

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

[Nottslad89]

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

[ematson5897]

Couldn't you just cut the antenna trace with a hobby knife instead of scrape the whole thing off?

[mcutee]

Its very informative post.I have tried it on my device.There is improvement.

[suicidal.banana]

Nice tut, finally some actual insight!
Thanks, will prolly do this to my dongle(s) soon :D

[rushatrout]

is it compulsary to remove the internal antenna????

[Mrinny]

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?

[admunt]

it very good to do that but i need to make more than 100M from antenna by bluetooth and the antenna  signal can run follow cable around my country (mean use cable substitute antenna, if u can do please email tell me i pay u my mail: [e-mail]
thanks

[fcampbell]

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?

[TripleHelix]

I Love the smell of modification in the morning !!!

[themonkeyz]

Great Instructable! I did this for my Bluetooth dongle and where I was getting almost no signal it now stays at "Good" level. I didn't test it extensively but it seems to have at least doubled it range. I applied the same technique to a Wifi dongle. The circuit was a little different but it worked the same way. I had trouble soldering it and it became quite hot but nothing broke. I now see a lot more networks. I even see the AP of my WISP, wich is 2.5km away, from my basement! Ok, it's at -88db, and it probably wouldn't hear me but I didn't see it before. Next step would be to get my hands on that useless dish hanging on my apartment building's wall.

[spiritiak]

is it save for pc? !If i do mistake can it damage my pc?

[cornflaker]

Don't worry you would have to mess up really bad for anything bad to happen to your comp, I've even run a little motor out of an old camera straight off my usb (without even using a connector! XD) it sucked so much power that all my other usb devices simultaneously disconnected, and reconnected when I quickly stopped lol no permanent damage was caused though so yeah if that didn't wreck anything I don't know what will.

[decades]

this is a quarter wave antenna (one fourth of the wave at 2.4gigahertx is 30 mm. The speed of light divided by the frequency in megahertz if you like knowledge..

[cornflaker]

Um... what does that have to do with my comment??? lol

[adamsdead]

ROFL I'll bet that smelled for a while afterward (I've melted plastics with my soldering iron before NOT a good smell hehe)

[cornflaker]

Um, can I use some coat hanger for the antenna? I currently don't have any other kind of thick solid core wire...

[cornflaker]

Ok, I have some kinda thick solid core copper wire now (not quite as thick as yours but I'm sure it will do) But if I solder it on like in this picture, will it still work well? The dongle will be sideways when in use so the aerial will be pointing up vertically.

[cornflaker]

Damnit the jpg compression has made it so you can read the small writing, it just says that the yellow and red is the existing aerial and I'm going to remove the red.

[Pazzerz]

Now that I see the case to give me a reference for the antenna mod position, it looks like you could have forgone the hole in the case and just soldered the antenna horizontally, leaving it entirely inside the case. Was there enough room for that, or did you have other diabolical reasons not to?? =)

[cornflaker]

Yea, good idea. Just use a bit of electrical tape to stop it from shorting stuff... But those diabolical reasons sound kinda fun ;)

[Nottslad89]

Hi Ken, Yeah, the vertical antenna gives omnidirectional (360 degrees) coverage, while a horizontal antenna, radiates from its sides, with almost no signal radiated from the ends. That's the reason for the vertical config. As I said in the article, the end result of my experiment is as ugly as sin, but it works well. If you spend more than the ten minutes I spent doing this, you can obviously get a neater looking result. Good luck :-)

[Pazzerz]

Here's an idea: The little hole in the side looks like a great place to put an antenna out that rotates to fold along the side of the case. ???

[woody123]

would it not be possible to use the rotating and folding link from the bottom of a radio antenna?

[cornflaker]

Hmm ok, I might make mine come out the side though as I had previously tried to solder my own antenna on and made a very neat hole in the side of my case (looks like it came with it :D) although that didn't work very well as i had no idea about size requirements etc so I had a rather thin approx 10-12cm bit of insulated copper wire half of which I coiled around a pencil then left the rest straight. It looked pretty good, but didn't work so well... I ended up just ripping it off because it didn't virtually nothing and it was annoying trying to not bend it

[etlerd]

Why is 30 mm a critical measurement for the antenna?

[etlerd]

And how long was the original antenna track?

[etlerd]

I wish I could delete this comment, as I just read the explaination :( But instructables is throwing errors.

[fez_uk]

I like the idea of this and nearly bought the same dongle for the external antenna but thought it might unscrew like a wifi dongle. To my disbelief looking on the net it's actually a dummy antenna... Makes you wonder if this make of dongle is also really class1? Anyway as I said I like the idea but who wants a copper spike sticking out of their dongle. If knocked the track will come off the pcb and might stab yourself. I still will buy one of these due to the space thats inside the casing for adding extras. I'll probably make my own instructables showing what I plan. Cya around. Im also a Ham op.

[spiritiak]

Hmm it's really work........i am noob but i did it successfuly.......realy good tutotial....realy thx.

[depotdevoid]

Very nice, I've been thinking of picking up one of those cheapo bluetooth dongles, but I've been concerned about range. Knowing that I can mod it to increase the range means that even if it sucks, I can make it better. 5/5 stars.