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How to combine signals from two or more antennas?

MUX-8

The launch of a new transmitter for VHF band (MUX-8) has increased the possibility of receiving digital terrestrial television by several additional DVB-T programmes. In some cases the customers with "old" antennas were very lucky and without any additional investment could enjoy reception of the new stations. However, in most cases it was necessary to buy a second antenna for that specific band, or decide on a complete modernization of the whole installation.

Depending on the location and local reception conditions (topography of the area, distance from the transmitter, its power, polarization), the most popular option is two independent antennas for individual VHF and UHF bands. A question arose in the process:

How to connect antennas properly?

That is, how to combine the signals from both frequency bands to get the best reception parameters for all MUXes? There are many ways, and the final choice depends on several factors:

  • parameters of the transmitter or transmitters - their distance, transmitting power for VHF and UHF bands, transmission polarization;
  • type and number of receiving antennas used;
  • specifics of the installation itself, its size and number of supplied outlets.

Branch filters, popularly known as antenna diplexers, are devices that allow to collect/combine different frequencies coming from two or more antennas, thus allowing to send the whole signal to the installation via a single antenna cable.

Combining two antennas

The first and simplest way of combining signals from two antennas is use of a band diplexer, e.g. ZWR-210DC. This professional diplexer has independent inputs dedicated only for particular bands, to which signals from appropriately selected receiving antennas are connected.  This way we can make sure that only the right signals are combined. Its additional advantage is possibility of feeding preamplifiers in any of the antennas.

For many locations, in case of using two passive antennas, there is a need of independent amplification of one or two bands. In such a situation the ideal solution may be application of a band micro amplifier, e.g. WSS-2138Z.  It features dual VHF and UHF inputs and independent gain control for both frequency bands. After the gain adjustment (appropriate for the specific installation) is made, the signal is combined and passed to its output for further distribution.

Combining several antennas

It also happens that the installation, aside from combining the signals from two bands, requires adjustment of amplification levels in the UHF band, due to different transmission powers of MUX 1, 2, and 3. Here, you can sucessfully use channel amplfiers, e.g. WK-410. This amplifier has 2 independent UHF inputs, one VHF input and one UKF input. Its primary task is to select four signals of different levels received in the UHF band in order to equalize them and then add them to the other signals (VHF and UKF).

The antenna and good coaxial cable are the basic and most important elements of audio/video installation.  The strength and quality of the signal delivered to the receiver depend on them.  Often, however, to be able to take advantage of all reception possibilities, we have to base our installation on several antennas, collecting signals from different directions and with different strength. To make such an installation work properly, it is no longer enough to use a simple branch filter or a simple mast amplifier. Professional, multi-band channel amplifiers from the WWK range are used for this purpose. With their help we can filter and adjust the signal levels to the requirements and needs of any, even the most complex antenna installation.

 

As always, we have to remember about quality of the installation - selection of appropriate cables and connectors, and proper crimping. Only then we can be sure that the installation will work faultlessly for many years and provide us with the highest quality signal.

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