Source: http://www.offel.it/eng/Support/Technical-support/FAQ/TV-mixers_-amplifiers-and-TV-multiband-amplifiers
Timestamp: 2019-04-19 14:55:12+00:00

Document:
FAQ: TV mixers, amplifiers and TV multiband amplifiers - Offel S.r.l.
How can I combine one or more signals coming from a different direction than everyone else?
It is possible to use special models of band and channel mixers, which have a channel input for receiving the signals coming from a direction and a broadband input, with traps in correspondence to the filtered channels on the other input, for receiving all the other signals.
I have some problems to receive RAI channels. How can I solve them?
When RAI channels come from a different direction than the channels transmitted by the other broadcasters, you can use different types of mixers and multiband amplifiers with broadband and channel inputs. In order to identify the product that best meets your needs, you can consult our Applications for regions area.
I have some problems to receive MEDIASET channels. How can I solve them?
When Mediaset channels come from a different direction than the other channels transmitted by private broadcasters, you can use art. 22-162, which is a mixer with broadband and channel inputs that allows, by means of a filtered input, the reception of the Mediaset channels only and the reception of all the other channels by means of an UHF input with traps in correspondence to the filtered channels.
What kind of amplifier can I use in environments with critical conditions (e.g.: attics with high temperatures, insufficient ventilation, etc.)?
The multiband amplifiers FUSION series are ideal in environments with high temperatures and insufficient ventilation, thanks to their die-cast aluminium case and the use of switching power supplies that allow you to deliver high currents keeping low temperatures.
What is the difference between a mixer, an amplifier and a multiband amplifier?
Mixers are passive devices with two or more inputs that allow to combine signals coming from several antennas by inserting a small insertion loss.
Instead, multiband amplifiers (both for indoor and outdoor) can be compared to amplified mixers: they are characterized by one or more inputs that allow to amplify the signals received by several antennas and to mix them on a single output.
Finally, amplifiers can be divided into broadband and channel models and are generally used to amplify the signals of a single antenna which have a lower level than those of the other.
The situation is different for in line amplifiers, which are broadband amplifiers characterized by one input and one output, which are used to amplify the VHF and UHF bands along a distribution line.
How can I choose the multiband or in line amplifier that best fits my needs?
In the in line amplifier choice the maximum signals output level and the maximum gain are the most important characteristics. For the gain choice you have to consider all the insertion losses of the system from the point where the amplifier will be placed to the outlets.
Once established the necessary gain, you can select the model with the appropriate signals output level. This level can't be exceeded, otherwise there may be problems of intermodulation and the in line amplifier doesn't work in linear way anymore.
In the multiband amplifier choice, first of all it is necessary to identify signals coming from different directions, which define antennas and multiband amplifier inputs number and type. Once done this, act as in case of in line amplifiers.
I purchased an in line amplifier for amplifying the signals along the distribution, but I got a worsening rather than improving. How is it possible?
• may be a problem related to the maximum permitted level of the input signals to the new TVs and DTT decoders on the market, which allow input signals with an intensity less than that received by the old analog tuners. It is advisable to keep the signal levels at the outlet of between 49 and 65 dBuV.
To check the real nature of the problem it is in any case necessary to perform measurements using a field meter.
How can I modify a channel inserted into the amplifier 26-700 REVOLUTION?
If You want to modify a channel in programming of the programmable filters amplifier art. 26-700 REVOLUTION You need to move the cursor on the channel to be change and then press the selection knob once. So You can change the channel and its conversion rotating the selection knob.
I inserted a wrong channel in the 26-700 REVOLUTION and I want to remove it. How?
If you want to remove a channel from the programmable filters amplifier art. 26-700 REVOLUTION inputs, you need to select the channel you want to erase and press the selection knob for 3 seconds. The channel will be removed and can be replaced it with another one.
Doesn't matter if the channels are in numerical order and can also be insert them in random order.
Why I can't insert the channels I want in the inputs of art. 26-700 REVOLUTION?
The amplifier art. 26-700 REVOLUTION is equipped with 5 inputs: 1 for the FM band and 4 for the VHF or UHF bands. When programming the channels on the VHF/UHF inputs, it is important to note that selecting the first channel selected determines if the input you are programming will be VHF or UHF. This means that VHF and UHF channels can not be combined in the same input.
I don't receive anymore the signals very well. Why?
When the signals aren't received correctly at the output of the amplifier, it is necessary to check the quality of the antenna by using a measuring instrument.
If the quality of the signals received in the antenna is acceptable, it is necessary to check that the programmed channels on the inputs of the amplifier art. 26-700 REVOLUTION are the desired ones and, if necessary, you have to modifying the programming.
I checked that the signals received from the antenna connected to the input I'm looking at are of good quality, but at the output of the amplifier art. 26-700 REVOLUTION I don't get them well. Why?
First, you have to check that the amplifier art. 26-700 REVOLUTION isn't intermodulating (the maximum output level must be 100÷103 dBμV). If the amplifier doesn't intermodulate, you must ensure that all antennas connected to the inputs are properly installed and functioning.
Then it's necessary to verify that the programmed channels on the other inputs of the amplifier are correctly received from the respective antennas, because if not the filters programmed on these channels could introduce noise and damage the signal quality also on the other inputs.

References: art. 22
 art. 26
 art. 26
 art. 26
 art. 26
 art. 26
 art. 26
 art. 26