Speed ​​up the 3G modem using an external antenna

All 3G modems have internal antennas. In some models there are even two or three. Nobody thinks about these antennas until the modem pumps five to five Mbps through itself without problems. But if the speed is a few kilobits, and if the computer with the modem has already visited all corners of the room in search of at least some signal, but did not find it, then the first thing that can help is an external antenna.

Some modems have a special connector for connecting an external antenna. The disadvantages of this method:
- it is necessary to find an adapter cable with a suitable connector specifically for this modem;
- there will be extra signal loss on the connector;
- The connector is very fragile, and a couple of inaccurate connections can break it.
Of the advantages of this connector - only its presence.
Many models of modems do not have such a connector. Just to such a modem we will connect an external antenna. For this, from the tools you will need: a screwdriver, a soldering iron, a sharp knife. As well as the ability to solder or extra money for a new modem.
So, our patient is the 3G modem Huawei E171 from MTS:

Carefully open the case and remove the modem from it. Here is its flip side (but it is not interesting to us).

On the front side there are: a module for a memory card, contacts for a SIM card, a radio module under the cover, a connector, an internal antenna and a USB output.

It is interesting that this connector is not available without disassembling the case, that is, almost all owners of this modem do not even suspect this connector. Let it remain in place, we do not need it and does not interfere at all. And the internal antenna prevents us:

The antenna is etched directly on the board, and we need to disable it. To do this, first bite out the SMD capacitor, designed for resonant antenna matching. Then we make a small cutter clamped into a drill and cut it along the antenna, leaving only a small area for soldering the cable. We make the cut shallow, since the printed circuit board is multilayer. We call the tester whether the “amputation” was successful and whether there is a short circuit between the cable soldering pad and the cut-off antenna. By the way, sometimes this platform can have a short circuit to the ground - these are the architecture features of some modems. If we had not cut off the internal antenna, then after connecting the external antenna, the signal would be divided between them, there would be a mismatch and nothing would work.

I wonder if there is still a chance to return this modem under warranty?
It should be noted that in some modems the internal antenna is made in the form of a cap with radiating elements. This cap is easily pulled off the board, so you don’t have to cut anything.
After the “amputation” we take a piece of RG174 coaxial cable with a resistance of 50 Ohms and a length of 15 cm (longer is not necessary, since such a cable has large signal losses), an F-connector and a “tulip” type connector. You can find all this in the radio parts store.

From the “tulip” we twist the cap, discard the rest. We clean the cable.

We solder the core to the central terminal of the F-connector, the braid on its ground, put the cap on the connector.

We carefully measure and drill a hole in one of the halves of the body. Pass the cable through this hole.

Solder the cable to the modem. We solder quickly, accurately and accurately, do not overheat the board. We solder the central core to the platform remaining from the internal antenna; solder the braid to any place that is ground and located as close as possible to the site with a soldered central core.

We collect the modem. Now a cable sticks out of the modem and prevents the lid from closing completely. Therefore, we carefully milling it.

We make a cable assembly up to 15 meters long and connect an external 3G antenna at a frequency of 1900-2200 MHz with a gain of 14 dB to the modem.

It's time to check this design in action. For the test, Huawei E171 modems from MTS and ZTE MF190 from Beeline were soldered. Two more exactly the same modems were purchased - as standards, so that there was something to compare.

The purpose of the test was to evaluate the increase in 3G Internet speed of a soldered modem with an external antenna compared to a reference modem with a standard internal antenna. In no case did we find out which of the operators is “better” or which model of the modem is “more correct”. We compared only a modem with an external antenna and a modem with a standard antenna.
Measurements were taken in an ordinary apartment, in a residential area. We measured the speed with a speed test, each measurement was done 10 times and then we found the average value.
Here are the results:

ZTE MF190 with a standard antenna (Beeline, 3G mode)
  • Ping 218 ms
  • Downlink 0.46 Mbps
  • Uplink 0.16 Mbps

Soldered ZTE MF190 with external antenna (Beeline, 3G mode)
  • Ping 99 ms
  • Downlink 1.16 Mbps
  • Uplink 0.66 Mbps

Huawei E171 with a standard antenna (MTS, EDGE mode)
  • Ping was not
  • Downlink 0 Mbps
  • Uplink 0 Mbps

Soldered Huawei E171 with an external antenna (MTS, 3G mode)
  • Ping 310 ms
  • Downlink 0.47 Mbps
  • Uplink 0.03 Mbps

Beeline 3G was caught on both ZTE modems, but a modem with an external ping antenna is 119 ms better, the reception speed is 2.5 times higher, and the transmission speed is 4 times higher.
I did not catch a Huawei modem from MTS with a standard internal 3G antenna at all, EDGE caught only a couple of times, there was no talk of any speed test or loading of any site. But it’s even more interesting - to catch a signal, it would seem, in a completely hopeless case! And it was possible with an external antenna: ping was equal to 310 ms, the reception speed was 0.47 Mbit / s, and the transmission rate was 0.03 Mbit / s. Moreover, during the tests we put the antenna on the windowsill and directed it randomly, just towards the street. It seems that when installing the antenna outside the window or on the roof, and with its competent pointing at the base station, the results would be much better.
As a result, a soldered modem complete with an external antenna gives a gain in speed at least twice, and they can stretch the signal where it never was. This is a real find for those who have not yet had any optics, or even copper.

Also popular now: