Combiner Request Guidelines

The system engineering of a multiple-channel Combiner requires several data to be collected. When requesting a quotation please specify as much information as possible, completing the following guideline table:

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Data Values Notes
Operating band UHF, VHF B.III, VHF B.I, DAB, FM
Standard DVB-T/T2 8 MHz, ATSC, ISDB-T, DAB Case 1, etc.
Configuration Mask-Combiner / No-Mask-Combiner A Mask-Combiner configuration is required for Adjacent Channel Combination
Adjacent Channel Combination Yes / No Adjacent channels (at least one couple) usually require a Balanced Combiner
Constant Impedance requested Yes / No A Constant Impedance request requires a Balanced Combiner with the Wideband port not used (terminated with Load)
Presence of existing channels to be combined Yes / No The presence of existing channels to be combined requires a Balanced Combiner
Wideband Port Configuration
(in case of Balanced Combiners)
1. Used to combine existing channels
2. Terminated with load
3. Used to combine (new) channels
1. Mandatory solution if there are existing channels to be combined
2. Most expensive solution; required if Constant Impedance or future expansion of the Combiner is requested
3. Cheapest solution; not compatible if Constant Impedance or future expansion is requested.
Existing channels to be combined (if any) Channel list with: channel number or Frequency, input power of each channel
(New) channels to be combined Channel list with: channel number or Frequency, input power of each channel
Forced Air Cooling accepted Yes / No
Liquid Cooling accepted Yes / No “Yes”: Trasmitters have to be liquid cooled

Balanced Combiner Chain and Wideband port use

The Wideband port of a Balanced Combiner allows to cascade several Balanced modules (also with different cavity sizes or different number of poles). The result is a Chain Combiner composed of n Balanced modules, having n Narrowband inputs and one Wideband input. The remaining Wideband input can be further used to extend the combiner combination capability:

Wideband Port Use Extended combination
Connected to existing Combiner Existing channels added to the new Balanced Combiner
Not used (Terminated with Load) 0 channels added; Future expansion possible;
Provides Constant Impedance for all channels
Single Filter 1 extra channel combined
Starpoint Combiner 2 extra channels combined
Manifold Combiner Several extra channels combined

Peak Voltage and Wideband Power

Voltage Peaks
COM-TECH Balanced Combiners have been dimensioned to widely sustain the increased voltage peaks caused by the vector composition of several signals (up to 10 channels).

Wideband Input Power
COM-TECH Balanced Combiners have been dimensioned to withstand the overall output power even in Wideband mode (the Wideband input power having a double impact on hybrid couplers), thus making the calculation of the total output power extremely easy:

Maximum Output Power = Sum of NB Input Powers + Sum of WB Input Powers

Wideband Tuning Optimization

The Wideband port Return Loss can be optimized either for the best value on specific channel(s) (at the expense of reducing the performances outside the given frequencies), or to reach the best tradeoff value on the whole operating band.

Wideband Tuning Features
Channel Optimized Best values on the specified channel(s)
(reduced performances outside)
Whole-band Optimized Best tradeoff on all operating band

Combiners with MultiStep technique, available on DF Series UHF Balanced Combiners, have unparalleled Return Loss performances, allowing an almost optimal Return Loss value on all the operating band.

Return Loss on Chain Combiners

Tuning data reported on the Datasheets refer to one single Balanced module.
The combination of several Balanced modules involves a derating of the overall Return Loss, influenced by the number of combined channels, channel order and assortment, and adjacency. For basic reference, and in case Channel-Optimized Wideband tuning, the following table is provided:

No. of Modules Overall Return Loss (VSWR)
1 26 dB (1.11)
2-5 25 dB (1.14)
6-8 24 dB (1.16)
9-10 23 dB (1.18)

Insertion Loss on Chain Combiners

Tuning data reported on the Datasheets refer to one single Balanced module.
The overall insertion loss of a Balanced Combiner Chain is the sum of the insertion loss of the single module, increased by the sum of the Wideband insertion losses of the following modules:

 I.L. (Overall) = I.L. (Single Module ) + n x I.L. (Wideband)