We catch someone else’s WiFi at a distance of 1 km

Published on November 15, 2016

We catch someone else’s WiFi at a distance of 1 km


    In a  previous article, we looked at options for increasing WiFi coverage for routers with external whip antennas. But consider the situation “on the other hand”, in which the built-in network adapter of a laptop or PC does not see the network well, as a result of which the WiFi signal is received at a low level, and in some cases, the desired WiFi network is not visible at all. Of course, it should be understood that the built-in WiFi adapter does not have a directional antenna and its tasks are completely different than “long-distance reception”.

    We list several situations where you can encounter a similar problem.

    - At a camp site, in a hostel, a sanatorium where WiFi is at the reception, and in your room, at best, 1-2 network divisions are caught;
    - On a bench on the street, where across the road there is a cafe with free WiFi, which seems to be close at hand, but the level is not enough;
    - You live with relatives or friends in neighboring houses, you have WiFi, but for some reason they don’t have it and it would be great to pass it wirelessly.

    And many similar situations in which we find ourselves regularly.
    So, what are the options for solving this problem? The first one that comes to mind is the option of using an external antenna to increase the range of the adapter, but unfortunately, it does not have a built-in adapter and an external antenna input for connecting antennas.

    You can use a USB WiFi adapter with an external whip antenna for better effect (Figure 1). However, this will not give a tangible increase in range. The fact is that such a whip antenna will be non-directional, and the gain with its dimensions will be low, as a result of which it will not be possible to increase the range of the adapter at times.

    Figure 1. USB WiFi adapter with external whip antenna

    You can use a USB WiFi adapter with an antenna connector and connect a directional antenna to it, but this design will be quite bulky and complicated. Nevertheless, this is not a mass option, because not everyone wants to make such a design. And it’s not cheap.
    In the end, you can use a regular WiFi router and connect it via a twisted pair cable to a laptop, however, again, this is not a very convenient and not the cheapest way in our opinion. This decision has the right to life, but the mobility and compactness of such a system can be forgotten.

    So, we have only a laptop or PC with a built-in WiFi adapter, which has a small radius of action. Task: to receive a signal of a remote WiFi network with a good level. After analyzing the situation, we came up with a solution “WiFi Agent” and want to tell you about it.

    Figure 2. WiFi Agent device render

    This device is a mobile USB WiFi adapter with a powerful directional antenna that allows you to see remote wireless networks with a good signal level and connect to them at a great distance.

    The basis was a patch antenna with a gain of up to 15 dBi, which has a pronounced radiation pattern in the frequency range 2.4-2.5 GHz. An antenna and a WiFi adapter board based on the RTL8188 chipset, interconnected by a coaxial cable with a length of about 10 cm, are located in a case made of radio-transparent plastic, which minimizes the loss of the RF signal in such a transmission line to a minimum.

    To connect the antenna to the computer, a USB type B connector is output on the front of the case, through which the device is connected to a laptop or PC using the supplied USB (type A-type B) cable. The user can use his cable of arbitrary length, but in this case it should be remembered that a cable that is too long will have high ohmic losses on the power buses, and this may lead to the device not being detected by the computer, or periodically “falling off”.

    In order not to be unfounded in evaluating the range of our device, below are the test results in various real conditions.

    In the first experiment, the engineers had the task of testing the capabilities of the “WiFi Agent” in a dense urban area. We know that for radio waves at frequencies of 2.4 GHz, walls of buildings and even trees can serve as interference. For convenience, we decided to remove not the receiver (our antenna), but the signal transmitter: WiFi router. The receiver is located stationary at the office window on the 2nd floor of the industrial building and is directed to the road along which our engineer with the transmitter will be removed from the receiver.

    As a WiFi signal transmitter, a portable router with autonomous power was used (Figure 3). The router is connected to a 4G network and distributes WiFi network - MF90PLUS_A5B14F.


    Figure 3. Self-powered portable router


    Figure 4. USB WiFi adapter with omnidirectional antenna

    Testing WiFi Agent in the industrial zone

    So, the measurements were carried out in urban conditions, in the industrial zone - fairly dense development of 2-3-storey buildings of industrial buildings, the receiver was located at a height of 2 floors of the industrial building, which also complicated the reception of the signal. The measurements were taken at a distance of 163 meters between the receiver (WiFi adapter) and the transmitter (router).

    First, we use a regular USB WiFi adapter as a receiver (see Figure 4), based on the RTL8192 chipset with a built-in omnidirectional antenna. Connect it to the laptop and run the InSSider Home utility (or any other convenient for you) to monitor the WiFi network level (see Figure 6).

    Figure 5 shows the profile of the terrain where the tests were conducted.

    Figure 5. Profile of the area where the first experiment was conducted

    Figure 6. WiFi networks visible through a regular USB WiFi adapter based on RTL8192

    As you can see, the network level is very weak (-87dBm), we were barely able to connect. Unfortunately, the response time for the speed meter’s website page has expired and the data has not even been downloaded.
    Take the WiFi Agent directional antenna “WiFi Agent” as a USB receiver. (see Fig. 7-8), we connect it to the same USB port of the laptop instead of the usual USB WiFi adapter.

    Figure 7. The directional antenna “WiFi Agent”.

    Figure 8. WiFi networks visible through WiFi Agent

    The signal strength of the network grew by 15 dB to −72 dBm. Also, it was possible to find 2 more new networks.

    Let's take a speed measurement (see Figure 9).

    Figure 9. Measuring connection speed while using WiFi Agent
    With further removal of the transmitter, direct visibility is lost due to trees and buildings located on the radio path, so the experiment was completed.

    Results of the first experiment

    As a result of the first experiment, in conditions of difficult reception of a microwave signal, stable reception of a WiFi network (level –72 dBm) was achieved at a distance of 163 meters in a straight line. It may seem that this is a comparatively short distance, but it must be understood that a portable standalone router with a built-in antenna was used as a signal source (transmitter), which is inferior to ordinary room routers with a remote whip antenna in the level of antenna gain and radiated power.

    The “Wi-Fi Agent” reception range will depend not only on our antenna (receiver), but also on the transmitter (router) to which you want to connect. We declare this with confidence, since we have conducted many tests of the device with different transmitters.

    Testing “WiFi Agent” in a residential building

    In the second experiment, the goal was to assess the capabilities of the antenna at a great distance from the transmitter with direct visibility in open space, and there should not be any serious obstacles to the passage of the microwave signal between the receiver and the transmitter on the radio path. To comply with all these conditions, measurements were carried out on the 7th floor of a nine-story residential building. As receivers, we used a USB WiFi adapter based on the RTL 8188 chipset with an omnidirectional antenna and our device.

    As in the first experiment, we will first measure with a regular USB WiFi adapter. We connect the adapter to the laptop, run the utility for monitoring WiFi networks. Figure 10 shows the list of networks that the adapter sees. Among them there is a network with the address of the house “Antonova d_.kv._” with a low signal level of −88 dBm, and we will follow it. Pay attention to the signal level of the other networks, presented in the same figure in the diagram below, it is quite low.

    Figure 10. List of networks visible through a regular USB WiFi adapter based on RTL 8188

    Connect our product and take readings (Figure 11). The level of the measured network rose to −79 dBm, and in general, the signal level of other networks also increased. Estimate the distance to the transmitter.

    To do this, we construct the profile of the route, given that we know the house in which the source of the network we are studying is located (Figure 12). As a result of measurements, we obtained a reception range of 1.02 km, while the difference in signal gain relative to the WiFi adapter with an omnidirectional antenna was 9 dB in favor of our antenna.

    Figure 11. List of networks visible through WiFi Agent

    Figure 12. Terrain profile of the second experiment


    It is worth mentioning programs that can help you when working with any kind of WiFi adapter for monitoring the level of WiFi networks *

    " WirelessNetView
    " NetSpot
    " Free Wi-Fi Scanner

    " LinSSID
    " iwScanner

    OS X:
    " NetSpot

    Please note that some software can be presented in the form of demos and have shareware distribution.

    Finally, we make a digression. One of our customers, having got acquainted with our device, was very surprised by its possible use and wrote to us - you made WiFi theft equipment!

    Of course, an attacker can use the “WiFi Agent” for illegal purposes. But, with the same success, you can blame the sellers of axes that the new "Raskolnikov" will buy an ax and attack the old woman-percent. And the sellers of dishes are generally accomplices of criminals. There are knives, rolling pins, and a terrible tool - a cast-iron frying pan.

    In the light of the latest laws adopted, it should be noted that our device does not contain any cryptographic encryption tools and is not a WiFi router. The USB WiFi adapter with the “WiFi Agent” directional antenna does not use any means to break into other people's networks and does not make the process of “theft” any iota easier than a regular laptop’s WiFi adapter.

    We believe that the issue of using any devices within the law is the direct responsibility of the consumer. Therefore, of course, when making any action, it is always necessary to remember the legal side of the issue.

    We recommend using the “WiFi Agent” in situations where the standard WiFi adapter of your laptop or PC receives a low-level WiFi network signal, as well as in cases where you need to use your WiFi network at a great distance from the router.