How to Increase Bluetooth Range

Its been quite a while since i have been using a wired earphone for my computer and very recently i switched to Wireless earphones. My Computer being a custom made, doesn't has inbuild Bluetooth because i didn't use Bluetooth earphones before. For a quick hack, i bought cheap Chinese USB Bluetooth adapter dongle, which are good enough for 1-1.5 meter range, but as soon as you go beyond that, these micro tiny devices get disconnected and this USB dongle becomes useless, so i came up with this simple yet permanent fix for this miscalculated problem. So today in this blog, we will solve Range issue of our USB Bluetooth adapter using Wire antenna which is typically piece of copper wire soldered on pre-existing circuit. Read to the end of this blog and i promise this will be the only mod you need to do on your bluetooth usb dongle ever!

We will require the following parts for this build.

Parts:

1. USB Bluetooth Dongle. [Amazon India | Banggood | Gearbest | Amazon Global ]
2. 0.8mm (21 Gauge) Enamel Copper wire. [Amazon India | Amazon Global ]

Tools:

1. Soldering Iron.
2. Hot Glue gun.
3. Vernier Calipers.

Miscellaneous:

1. Calculator.
2. Box cutter blade.

Theory Behind this problem:

Bluetooth is a low tier WBAN (Wireless Body Area Network) Technology, ad hoc, terrestrial, wireless standard for short-range communication. The IEEE 802.15.1 standard contains the Bluetooth specification. It is designed for small and low-cost devices with low power consumption. The technology operates with three different classes of devices: classes 1, 2, and 3 where the range is about 100, 10, and 1 m, respectively. The USB Bluetooth Adapter we are using is class 2 device, with range of upto 10 meters.

On further inspection, it was found that the circuit had only 1 IC for communication and radio, which is practically not sufficient for high power RF (radio frequency) communication.

Following Figure describes the transmission of one-slot-type packet between a master and a slave. The master transmits a packet in a slot and the slave sends the data to master in next time slot. The time slots need synchronization between the master and the slave. Since our device is a micro receiver, it will need comparatively more power to finish its task.

Conclusion:

The main problem in our Circuit is Range, while the exact reason could be understood by the choice of antenna in this circuit, which is mainly due to size and price constraints.

The antenna system used for any radio communication platform is one of the critical parts of Wireless Communication system. The antenna system is the interface between the radio system and the external environment. Wireless communication systems require antennas at the transmitter and receiver to operate properly. There are many types of antennas available, all of which perform specific functions depending on the application at hand. The type of antenna used by a system operator can be colinear, folded dipole, or Yagi, etc.

The performance of an antenna system is not restricted to its gain and physical attributes, but also depends on other parameters that must be considered in evaluating antenna performance.

The parameters that define the performance of an antenna system are:

Antenna pattern, Main and side lobe, Radiation efficiency (η), Antenna bandwidth, Horizontal beam width, Vertical beam width, Gain (G), Directivity (D), Antenna polarization, Input impedance, Front-to-back ratio (RFB), Front-to-side ratio (RFS), Power dissipation, Intermodulation, Construction Cost.

But, depending on application, range, and many other factors, few of these parameters can be neglected to get desired results.

There are many types of Antenna like :

• Wire Antenna.
• Aperture Antennas.
• Microstrip Antennas.
• Array Antennas.
• Reflector Antennas.
• Lens Antennas.

There are many subtypes of these antenna, but lets stick to the simplest form of antenna and which is most relevant to our project, that is Wire Antenna.

Wire Antenna:

Conducting wires are material whose prominent characteristic is the motion of electric charges and the creation of current flow. Let us assume that an electric volume charge density, represented by qv (coulombs/m3), is distributed uniformly in a circular wire of cross-sectional area A and volume V.

The Wire Antenna can be configured in following ways:

Now you must be thinking why exactly do we need to use Wire antenna? the biggest reason here is to improve our range and signal capabilities.

If you see closely to the Electric field lines of free-space wave for Wire antenna, its clear that we get a 360 coverage, where as the pre-existing antenna on the USB receiver was a microstrip patch, which has the following pattern:

Now by comparison, its very clear that for our purpose of Bluetooth dongle, its very effective to use Wire (monopole) antenna instead of pre-existing Microstrip patch antenna.

Conclusion of Antenna Theory:

We need to use a Monopole antenna (wire) instead of Microstrip antenna for our suitable purpose and we can neglect certain parameters while considering our set example.

Like we discussed in last section, we are using a Monopole ( wire ) Antenna. and the configuration that closely matches our pre-existing circuit is a Quarter wave antenna, so we will use the Following Formula for quarter wave antenna designing.

Also, here the Relation of c = λ*f.

where C is Speed of Light and F is Frequency of signal, λ is Wavelength.

therefore, Wavelength:

λ = c/f.

Quarterwave Length of Antenna.

L = λ/4.

On Calulation with respect to 2.4GHz of Bluetooth frequency, we get L ( length of antenna ) as 31.25mm. ( Diameter of antenna is 0.8mm ( +- 0.2mm works for the same).

Here is a link to Excel sheet which you can use to implement the given formula.

Steps:

1. Take 0.8mm Enameled copper wire.
2. Set 31.5mm on Vernier calipers.
3. Mark 31.5mm on copper wire.
4. Cut to marked length using pliers.

Once we have our Antenna made with appropriate calculations, its time to solder the Antenna on PCB (waveguide).

Steps:

1. Open the first lock of USB Bluetooth Receiver.
2. Slide off the metal USB slot of Receiver.
3. Remove the USB Bluetooth Receiver circuit from its enclosure.
4. Solder Antenna cut in previous step to the start point of waveguide as indicated in picture above.
5. Using hot glue gun, isolate the solder point to provide strength.
6. Put the Circuit back inside the enclosure the same way as removed.

After this last step, we are almost done with all the modification, lets get to testing!

On testing this modified system, we successfully got at least 6m of range which was before getting disconnected at 1m. In conclusion this was a very easy and successful modification of Bluetooth. No more frequent disconnection and irritation, now i can easily enjoy editing my videos, listening to music, watching movies, Netflix and chill or whatever would want to do with your Bluetooth.

I have been using it for a few days and I really really love it!. More than aesthetics, i enjoyed the build process. However, It took a lot of time in writing the theory part of this blog. I am counting on you guys to share your feedback on comments so that i can improve.

If you enjoyed this blog post or project, consider supporting our work by subscribing to our YouTube Channel (its free!) and following our Social media handles, your support means a lot to us and motivates us to keep making awesome content!

Social Media Handles: Patreon, Twitter, Instagram, Facebook.