Antenna Combiner vs Antenna Distribution: What Each One Does

They look alike and sit next to each other in the rack, but they run in opposite directions. A combiner handles signals going out to the stage; a distribution amp handles signals coming in from it.

The difference

• Antenna combiner, for IEM transmitters: takes the RF output of several in-ear transmitters and sends them out through one antenna. Without it, every transmitter needs its own antenna, and antennas packed close together interfere with each other.
• Antenna distribution, for wireless mic receivers: takes one pair of antennas and splits the signal to several receivers. Some models also power the receivers. Without it, every receiver needs its own pair of antennas.

Never swap them. A distribution amp won’t carry transmitter output, and a combiner won’t feed receivers.

Examples in the catalog

• Shure PA821A: an 8-to-1 combiner for PSM transmitters. Shure has discontinued it, and the PA821B is the current 8-to-1 model.
• RF Venue COMBINE4: a 4-to-1 active combiner for IEM transmitters, 470 to 960 MHz, that also powers up to four transmitters.
• Shure UA844+SWB: a wideband active splitter, 470 to 952 MHz, that feeds up to four receivers from one antenna pair and supplies 12 V DC bias to in-line antenna amplifiers.
• Sennheiser ASA 214: an active splitter for Sennheiser ew G3 and G4 receivers, two 1:4 banks for up to four diversity receivers, that also powers them. EW-D and EW-DX use the separate EW-D ASA.

When a rig needs each

• Two or more IEM transmitters in one rack: plan a combiner. Four stereo mixes means four transmitters, so a 4-to-1 unit is the smallest that fits; an 8-to-1 leaves room to grow.
• Two or more wireless mic receivers: plan antenna distribution sized to the receiver count, or use receivers’ own cascade ports when there are only a few. See the Shure receiver guide for which models cascade.
• Both: most band racks with in-ears and wireless vocals carry one of each, with the antennas mounted apart.

Preamps

Neither device touches audio, so neither uses mic preamps or console inputs. They do use rack space and an outlet each, and a distribution amp that powers its receivers changes the power plan. For the full RF picture, see antenna distribution for IEMs and wireless frequency coordination.

Sources

• Shure PA821A product page: antenna combiner for PSM systems, discontinued
• Shure PA821B specification sheet: current 8-to-1 PSM combiner
• Full Compass RF Venue COMBINE4 listing: 4 inputs, active, 470 to 960 MHz, powers four transmitters
• Shure UA844+SWB user guide: up to four receivers, 470 to 952 MHz, 12 V DC bias for antenna amplifiers
• Sennheiser ASA 214 product specification: two 1:4 banks, G3 and G4 receivers, powers receivers and antenna boosters
• Sennheiser EW-D ASA listing: active antenna splitter for EW-D and EW-DX systems