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Project 015 - Bluetooth Dongle - Range Extender

The wife doesn't have a PC proper, she uses a small PC that's connected to our 42" Plasma Tv in our living room. That PC/Tv combination also doubles as a front end/GUI for our entire music (MP3) collection stored on my Dvico Tvix6500A. I don't really use the Tvix GUI, prefer to use WinAmp.

However, the wife has an Iphone and is getting an Ipad so as far as using that PC for email it's become rather redundant. So, I decided to get rid of the PC.

WinAmp I moved to my web/email server PC at the other side of the house and use a great WinAmp plugin called AjaxAMP which basically gives WinAmp a web interface so can be controlled via wifi from any web browser.

Problem I'm left with now is that the WinAmp PC at the other side of the house has it's audio out jack many rooms away from my home hifi setup in the living room. So, I purchased a Bluetooth dongle for the WinAmp PC and a suitable Bluetooth (A2DP) receiver at the audio setup in the living room.

So, the control loop is as follows:-

- AjaxAMP on web browser on laptop (or Ipad etc) via Wifi controls WinAMP on Server PC on Lan.
- Tvix6500A also on Lan stores the MP3 files, so any music played is streamed across the hard wired Lan.
- Bluetooth dongle on Server PC streams music wirelessly to Bluetooth receiver in living room.
- Audio output from Bluetooth receiver hardwired to amplifier/speakers.

And it works!, however, as most Bluetooth dongles are 10m range then it can be rather intermittent and will stop/start mid song. I guess the foil backed plasterboard in our house doesn't help (Faraday cage!). Grrrrr! So, I set about modifying the Bluetooth dongle to increase it's range. Turned out rather easy in-fact!

Most Bluetooth devices work at frequencies of around 2450MHz, the formula for which will give you an antenna length of around 12cm. Divide this by 4 to give a quarter wave antenna length of 30mm. This is the magic number, 25mm or 35mm will just make it less efficient and lower the range.

The net result is like chalk & cheese. With the original dongle I was getting constant dropouts, but as soon as I plugged in the modified unit it's perfect. I'll estimate the range of the original dongle at about 10-20m, but the modified one at least double that, maybe more.

So, here's a series of pics which demonstrate the job. First, the original dongle:-


The unit opened up you can see the antenna printed onto the board:-


Cut the antenna short and scrape the remainder off the board with a sharp knife:-


I used an old capacitor leg for the new antenna. Solder and glue it into place. Note that on this particular dongle the antenna doesn't start where I soldered it, it actually snakes (see the blue track) onto the board by some 6mm. Make sure you include this in your 30mm calculation.
This was just my test dongle, so preferrably I should have soldered the new antenna at the components where the antenna starts thus maximizing the single, uninterrupted, straight line of the antenna for best efficiency.........which is exactly what I did with the 'production' dongle that I have in permanent use:-


Here's it all boxed up again:-


The bluetooth receiver. This has stereo audio outputs that simply cable down to my Denon amp & speakers. Actually, I've had this unit for a while as it is also a Bluetooth transmitter and can stream audio/music to Iphone's/PC's etc.....but thats another story!:-


AjaxAMP running in my web browser on my laptop, but can just as easily be from Safari on an Ipad. Matter of fact I tested this and it works, so Apple have made a great remote control.....:-).
PS. Yes, I own all the CD listed below (I'm a big Eagles fan!):-


Here's AjaxAMP running on my mobile phone (HTC Desire):-


Winamp Pro running on the Server. There is a small amount of latency because the MP3's are located on the Tvix6500A, but it's hardly noticeable on a 1gig Lan.
Winamp will sit minimized in the system tray as this screen is not normally seen (doubles as web/email server), heck, this PC doesn't even have a monitor, I log into it using remote login.