Band Pass Filter For UHF Transmitter : Why do you need it?

Most, if not all,  transmitters will require some sort of filter at the output of the final amplifier or power amplifier. The main reason for requiring a filter is to remove any out-of-band spurious signals or harmonics from the output of the power amplifier before connecting the output of the transmitter to the antenna. This will prevent spurious emissions and ensure that the operation of the transmitter will not cause interference to other systems.

Similarly, a UHF transmitter also need to have a band pass filter for the same reasons.

 A Layman’s Look At The Functions Of Band Pass Filters For UHF Transmitters

If you live in the suburbs, or in a far-away town, and your TV’s UHF channels often get disrupted, or have a poor reception (like pixelating screens, picture cutting out, or poor sound) it could be due to the interference of mobile phone transmissions, or other VHF frequencies. The good thing today is that these interruptions and distortions are now either considerably reduced, or eliminated, with the invention and widespread use of UHF filters. If you’re not an electrician, or an electronics and communications hobbyist, here’s a quite layman’s look at the functions of band pass filters for UHF transmission.

UHF Filter Removes Disruptive VHF, FM And Mobile Phone Signals

If you experience erratic, or poor-quality signals or reception on your UHF TV channels, an ordinary technician will assume that low signal levels are the main culprit or symptom. However, the truth is that the UHF signals in your area are caused by very high levels of VHF and/or mobile phone signals. This is where a band pass filter for UHF transmitter becomes a very helpful tool.

A UHF bandpass filter removes excessive or unwanted VHF, mobile phone and FM signals, and lets UHF signals exclusively pass through the transmitter or TV receiver/antenna.

What’s A Standard UHF Filter Made Up Of?

In television, the UHF band is made up of 45 channels, which are numbered from 21 to 65, and of which selectivity rules or standards are imposed, in order to achieve this selectivity throughout the band.

And in the distribution of TV channels or signals, it’s crucial to supply signals having a uniform level, and this is where UHF filters are of great help. A conventional UHF filter is made up of an input and an output, and at least two resonators, with each one arranged in their respective cavity. These types of UHF filters are normally used for filtering the different TV channels in cable networks.

But in conventional UHF filters, where the coupling between the resonators is adapted by hand, through the use of conductor wires whose correct or appropriate, position for attaining the desired bandwidth and selectivity around the central frequency of each channel, is quite hard to obtain or find.

However, the newer versions of the UFH filter are better designed, and are fully electronic, so only low-level signals  can enter, or pass through. For example, tunable UHF band pass filter tuners cover 470-860 MHz, and has a typical bass band of -7 MHz /-3 dB, along with a rejection rate of ~20 dB on each side, and ~ 5 MHz from center.

Most of the UHF band pass filters today are available for analog and digital, VHF or UHF channels, and these are installed at the transmitter output to reduce or suppress out-of-band emissions or signals, which may distort or interfere with the other channels.

Most band pass filter for UHF transmitters also feature medium to low loss, to fully maximize station coverage, and they can even be customized or designed to meet specific needs or demands.