Military expert explains how to use mobile repeaters

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mobile repeaters

LTE (4G), GSM (2G), 3G mobile communication repeaters are very important for use in the Defense Forces. Ukrainian specialist and consultant in the field of military radio technologies, tech blogger Serhiy Beskrestnov (Flash) explains how to choose and use the right equipment.

How the repeaters work

A range extender is a “box” that is powered by an outlet. On one side, a cable with an antenna is connected, which is directed to the operator’s base station, and on the other side, a cable with an antenna for indoor coverage is connected. The range extender amplifies the operator’s signal and the phone signal in both directions.

What is the difference between repeaters

1. Amplification

For repeaters, the concept of output power is relative. They have a value of end-to-end gain. That is, how much “came” to the input from the operator’s station and how much “went” to the antenna at the output. The stronger the signal at the input, the better it is at the output.

All low-cost repeaters have approximately the same gain parameter. It is difficult to increase it because the signal from the output will drown out the signal at the input. This is the main nuance of operation, which we will discuss later.

2. Operating range

To begin with, all low-cost repeaters are broadband and will strengthen all operators.

In Ukraine, operators use many bands, and they may differ from place to place. These are the 900/1800/2100/2600 MHz frequencies. Therefore, if you are installing a range extender for your home, you can find out the range of the nearest operator’s station and save money by buying a single-band range extender.

But if you’re going to the front, you need a multi-band repeater. After all, you cannot predict where fate will throw you and what frequencies will be available there.

For those interested, operators in Ukraine use frequencies in this way:

  • 900 MHz – for GSM and LTE;
  • 1800 MHz – for GSM and LTE;
  • 2100 MHz – for 3G and LTE;
  • 2600 MHz for LTE.

According to the expert, most of the stations in Ukraine are in the 1800 band. About 60-70% of the total number. However, the largest coverage is in the 900 MHz band. That is why these two bands are primarily important. After all, the upper bands are used for coverage in cities.

Сергій Флеш

Coverage area and efficiency

“It’s easy to tell if the range extender will work. If your phone picks up some signal, it’s worth a try. If you raise your phone to the height of the future antenna and there is no signal at all, then don’t waste your time, it will not help you. As I have already mentioned, the range extender has a through amplification and its coverage area depends entirely on a good outdoor antenna, a good cable, and the level of the incoming signal. If the situation is ideal, you will get a coverage area of 20 by 20 meters. If the range extender is cheap and the input signal is weak, you can have a communication area of even 2 by 2 meters,” writes Sergiy Flesh.

For those who are interested in understanding, he provides a more detailed calculation.

“For example, the gain level of the repeater is indicated in the description, 70 dB. Let’s say the signal “from above” on the air is -70 dB (from the division on the phone scale). The external antenna gave us +14 dB of gain, then we lost 3 dB in the cable and connectors, amplified by the repeater by 70 dB, then lost 1 dB in the second cable and amplified by the antenna from below by 3 dB. In total, we received +17dB of power from the bottom near the antenna. This is 0.05 watts.”

There is a more complex system with many antennas at the bottom that provide uniform coverage of large rooms, but these are special cases.

Antennas and cables

Let’s start with the cable. If you want all of this to work as well as possible, then you should use a “thick” RG8 cable from Belden, Kingsignal, Selteq, Andrew, Ericsson. Replacement options: LMR400, TZC 500.

The total length of the cables from the range extender to the antennas should not exceed 25 meters. Ideally, up to 15 meters.

The antenna that “looks” at the operator’s station from above is always pointed to maximize signal strength. Typically, a single-band repeater uses a waveguide antenna.

If the repeater operates on several bands, a log-periodic antenna is used (it is hidden in a plastic cone flat case). Or a flat panel antenna. You can also use a directional antenna “from below” if you need coverage in a certain direction.

Installation

This is an extremely important part. When installing it, you need to maximize the height of the receiving and transmitting antennas. This way, the output of the range extender will not interfere with the input and the gain will be maximized. The receiving antenna should be directed to the nearest base station. And don’t forget that the repeaters are not hermetically sealed.

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