Antennas for 3G Mobile Broadband Data Communication
So you got this flat rate 3G internet USB dongle and find that you have a slow or unreliable connection?
Read on how to improve mobile broadband speed with an external antenna for a better internet surfing experience...
Download speeds of 3G/HSPA data connections and connection reliability are heavily dependent on 3G signal quality. The signal strength depends on the distance to the base station, your equipment and on the surroundings of your work place. You can compensate for weak elements in this chain by using a suitable additional antenna. With an appropriate antenna one can typically improve data throughput by a factor of 2 to 10. The graph below shows the throughput of the cellular connection while downloading a large file from a website. In this case, a Huawei E160 3G USB stick was used together with the ADPT-026 and the external antenna OMNI-A0121 mounted outside on the wall of the house. The speed of the download was 3-6 times higher with external antenna than without. The user experience is therefore greatly improved.
So what is the right antenna and how do you get it to work with your USB dongle?
There are two very important things to consider when you get an antenna:
Poynting’s antenna selection for poor mobile network reception areas
Different Antenna Types
In principle, antennas are classified as "directional" (sending and recieving in one specific direction) or "omnidirectional" (same sending and receiving all around the antenna).
Directional vs. omni-directional antennas, when to use what
The main issue is how good your signal is outside. Directional antennas in general have higher gain than omnidirectional. The rule of thumb is:
Installing an external antenna
Installing an omni-directional antenna is easy. The rule is: mount the antenna as high as possible outside on the wall of the house but do not increase the cable length unnecessarily. Cables dampen the signal (depending on cable quality). With an omni-directional antenna, the cable length should not exceed around 8m (low loss cable like LMR-195), otherwise all you gain with a good antenna would be lost.
Installing a directional antenna requires a bit more work. Again, mount the antenna as high as possible without excessively increasing cable length. With a high gain antenna like the LPDA-A0044, cable lengths of as much as 15m are possible (providing usage of high quality, low-loss cable). Then, the antenna needs to be aligned towards the nearest base station. If you use your 3G adapter or mobile phone in order to measure signal strength, you must wait up to 60 seconds until your display shows you the correct measurement. Turn the antenna by increments of 10° degrees to find the direction of strongest signal. It may help to check with your provider where your nearest base station is located. An alternative is to use a mobile spectrum analyzer to help identify the direction of the strongest signal.
A word on cables
Antenna cables play an important part on how well the antenna will work (and what it will cost). One of the commonly used cables is RG-58. It is cheap - but not good for frequencies above 1800MHz (like UMTS and HSPA). Cables like HDF-195 (also known as LMR-195) have the same physical dimensions as RG-58 but only about 0.55dB vs. 1dB loss per meter. If "dB" doesn't really tell you anything, here is an example: with 10m cable, you will end up with 28% of the signal at the end with HDF195, but only with about 10% with RG58. Make it 20m cable, and you are left with 8% with LMR195 and only 1% with RG58. This is also why it is so important to keep your cable short. The losses are dramatic. So don't be disappointed if your antenna with an RG-58 cable will not deliver what it promises. You get what you pay for.