Bluetooth USB Antenna?

[Alek]

Is it possible to extend the range of a USB Bluetooth adapter using a 2.4GHz antenna? Specifically, can I scratch off the tiny antenna on the PCB (at least I think that's the antenna) and solder a connection to an external antenna? Is this a good/bad idea?



This may not strictly be the correct place to post this, but it is about wireless and 2.4GHz antennas! Also didn't know where else to ask and you guys seem like you might be able to give me a good answer.

 

[paul_51]

Probably

Is it possible to extend the range of a USB Bluetooth adapter using a 2.4GHz antenna?

All WIFI antennas support the 2400-2484 MHz band, and typically the WIFI antenna is connected to a chip that does both WIFI and bluetooth. This means designing antennas for WIFI and bluetooth is basically the same thing.

I should guess that it is, though (full disclosure here) I am not familiar with Bluetooth at all.
The frequencies are practically the same: 2.4 to 2.485 GHz for Bluetooth, and 2.4 to 2.4835 GHz for IEEE 802.11. Also, I've read somewhere at some point that at these high frequencies you don't need a balun added, so there's that. The gain should be probably roughly equivalent to that achieved with the same antenna in WiFi applications.

Nonetheless, it's hard to tell whether what you're seeing is the antenna or not. Moreover, that thing is tiny and fragile, so consider hot-gluing both parts to a plank of some kind, and maybe putting it into a rigid plastic tube. You will need a matching female RP-SMA connector (source) with a few centimeters of cable attached. Also, don't forget that the stripped cable conductors must be as short as possible to minimize loss.

Have you looked into guides online yet? Andrew McNeil has a lot of DYI antenna instructional videos on YouTube. Here's a sample. Just make sure to stay away from instructables.com and abominations like the popsicle stick yagi.

 

[Alek]

Thanks for the links, Paul. And for the tips on using a female SMA and gluing to a stable base: I was going to cut off the SMA connector, strip the wire and solder that, but using the female connector is a much much better idea. Also gives me the flexibility to test different antennas should there be any need.

Furthermore, I think it makes good sense to separate the different parts so that they can be housed sensibly, fixed securely and easily swapped or replaced. I can use a simple USB extension cable to give the PCB some room and keep it fixed, so that IO can be mounted to the enclosure and not cause me any headaches.

Just bought a female SMA connector off a popular online marketplace for a whopping dollar, so that should get here in about a week or so. I'm in the middle of moving house, so I might only get to work on this sporadically, but will update this thread when I do. I am determined to get reliable bluetooth out of this damned thing!

Only aspect I'm still really unsure about is where to attach the female SMA wire on the PCB, but I'll do some more research and cross that bridge when I get there.

 

[sfx2000]

Is it possible to extend the range of a USB Bluetooth adapter using a 2.4GHz antenna? Specifically, can I scratch off the tiny antenna on the PCB (at least I think that's the antenna) and solder a connection to an external antenna? Is this a good/bad idea?

View attachment 2346

This may not strictly be the correct place to post this, but it is about wireless and 2.4GHz antennas! Also didn't know where else to ask and you guys seem like you might be able to give me a good answer.

Have you consider a Linksys USBBT100 dongle instead?

Alternately - I use an ANYCOM USB-250 for my bluetooth hacking - it's older, and the company itself is out of business - but it's a Broadcom chipset, and works well with Linux

 

[Alek]

Have you consider a Linksys USBBT100 dongle instead?

Alternately - I use an ANYCOM USB-250 for my bluetooth hacking - it's older, and the company itself is out of business - but it's a Broadcom chipset, and works well with Linux

I found it really hard to find branded class 1 devices like that, and I already have all these useless mini-dongles lying around. I'll get a cheap $2 no-name from HK and test it. The other reason is that I need the adapter to support HID proxy so that I can use it in BIOS/bootloader and be compatible with OSX, which limits me to Broadcom chipsets.

Still waiting on the female SMA to get started. I did find this tutorial on YouTube: Part 1 / Part 2. That guy uses an insane amount of solder though, might as well dip the whole thing in a vat of liquid metal. Seems like he, somehow, got it working though.

 

[sfx2000]

Hmmm... sounds like a lot of work - part of the problem I see with your adapter is how to mount an antenna on the dongle - might be better to put some coax and break it out into an SMA - then any wifi antenna would work (it's all 2.4GHz).

Also, consider, if you're doing deep dive into BT, you might consider an arduino and a BT shield instead...

The USB-BT dongle you have - it's pretty limited - try to find a Class 1 - that's the ANYCOM dongle I mentioned - I was able to keep a cheap BT headset in a Corp/Enterprise Wifi environment out to about 100 meters paired up before it dropped (nice to work in a building that is 1/4 mile long)... doing traces on Rx only, and I saw a 1/4 mile range before we lost the target device (another laptop with the same ANYCOM dongle)

The Linksys device I mentioned is interesting, as it has an external antenna anyways, so just unsolder it, put your SMA coax onto those points...

One other consideration - use a USB extender cable, laptops are pretty noisy in 2.4GHz, esp if WiFi is also being used.

good luck!

 

[Alek]

Well I decided to test out my sticking-a-huge-antenna-on-things-that-don't-have-an-antenna skills on this RF remote.



Not exactly elegant but it totally works! Still waiting on the SMA adapter getting here from China to start on the bluetooth dongle.