Manifold
Cascade of several filters on a common output transmission line (“Manifold”); one end of the line is shorted, while the opposite is the output (Antenna).
The solution to the filter interaction problem is assigned to the respective position of the filters on this line; the complexity is greatly reduced compared to the Starpoint, and it is possible to implement multiplexers with up to 10 or even more channels with a great efficiency.

COM-TECH was the first to introduce the Manifold technique to Broadcast TV and FM applications, and further extended the versatility of this architecture exploiting the Adjacent Channel combination.
The Manifold combination technique is available on UHF and VHF B.III (MX Series) and FM (ME Series) Combiners:

Starpoint
Multiple connection of various filters with a common junction.
The connecting lines are resonant in order to provide the open circuit condition at the junction node.
The implementation is always possible for 2 channels, and becomes very critical or even not achievable with more than 2 channels.

COM-TECH offers a complete range of Starpoint Combiners (2-Channel as standard, more on request).
The Starpoint combination technique is available on UHF, VHF B.III, VHF B.III DAB, FM (SB, SM, SF Series) Combiners:

  • Adjacent Channel Combination not possible
  • Limited number of channels combinable
  • Cost effective solution for 2-channel combination, or in conjunction with Balanced Combiners

Balanced (Constant Impedance)
Balanced structure of two identical bandpass filters and two hybrid couplers, creating a Directional Filter, having one Narrowband (filtered) input and a Wideband (non-filtered) complementary input.
Balanced Combiners are the definitive solution in broadcast combining systems, providing the best performances and versatility.

COM-TECH offers a complete range of Balanced Combiners, allowing Adjacent Channel combination (in conjunction with DualCross or XLine Filters), and Multi-Channel combination (up to 10 channels).
The Balanced combination technique is available on UHF, VHF B.III, VHF B.III DAB, FM (DB, DM, DF Series) Combiners:

Stretch Line (Westford Multiplexer)
Simple construction made of two hybrid couplers and a phasing line.
The result is a phase-shift filter with a periodic frequency response, having one input complementary to the other.
This combiner has major limitations, since the frequency responses fall at discrete intervals which are difficult to match with the desired channels; in addition its selectivity is very limited and thus does not make it possible to combine neighboring channels.

COM-TECH can provide Stretchline Combiners (2-Channel) upon request.