T121016AB
HEAD END COMBINER
MODEL HEC-4

PBE’s Head End Combiner (HEC-4) is the core of PBE’s
Minecom Leaky Feeder System. Its purpose is to
combine the RF outputs and inputs of the connected
equipment. The Head End Combiner provides the
necessary interface between the repeater equipment and
the Leaky Feeder cable. It is capable of providing up to
eight fully func+onal channels with connec+vity for up to
four 75 ohm Leaky Feeder coaxial cables.
OPERATION
The new design is more configurable and has less through
loss than other models, as well as op+onal internal gain
adjustments.
The HEC-4 has a flexible filter design to accommodate a
mul+tude of frequency bands. It includes SAW filters that
provide more stability over environmental condi+ons. It
also has higher isola+on across all frequencies than
previous models.
The HEC-4 has digital displays for monitoring the line
current and voltage of each leaky feeder port.
Eight BNC ports are used for transmi6ng (BASE Tx) to the
Leaky Feeder and eight BNC ports for receiving (BASE Rx)
from the Leaky Feeder. The Rx port incorporates
adjustable gain to maximise recep+on. The loop ports can
be used to connect Head End Combiners together to
provide more channels, or more Leaky Feeder ports.
Adjustable Leaky Feeder uplink gain allows increased offthe-
cable underground coverage. The HEC-4 has added
surface coverage, via an external antenna, as well as
auxiliary band interface op+ons. The auxiliary band port
provides access to the lower frequency downlink auxiliary
band, available in PBE’s BDA-4 amplifiers, and also
provides flexibility for possible future bidirec+onal
communica+ons in BDA UHF and VHF products.
The HEC-4 has circuit breakers, with Fault indica+on and
Reset bu;ons for dealing with short circuits or excess
current on arterials. The HEC-4 is also protected by a
M205 size 12.5 Amp slow blow fuse.
FEATURES
• 8 voice and data channels (supports up to 32 channels)
• Four Leaky Feeder outputs with op+onal DC supplied
• 12, 24, or 48 V DC compa+ble
• Front panel diagnos+cs
• High noise immunity
• 19 inch rack mount
• Universal design (supports VHF and two standard UHF
frequency bands without modifica+on)
• Flexible SAW filter design
• Supports direct surface Rx and Tx interface
• Eliminates the need for a duplexer
• Supports Auxiliary band
• External RF loop back connec+on for field tes+ng and
cascading of Head End Combiners
• Adjustable surface Rx port gain
• Adjustable Leaky Feeder uplink gain
• High Tx – Rx Isola+on
T121016AB
HEAD END COMBINER
MODEL HEC-4

TECHNICAL SPECIFICATIONS

Input Voltage: Mul+: 12, 24 or 48 volts DC
Input Current: 2.5 amps per LF Port max (10 A total)
Tx Frequency: 144 – 161 MHz; 403 – 413 MHz; 480 – 490 MHz
Rx Frequency: 169 – 186 MHz; 428 – 438 MHz; 450 – 460 MHz
Max Input RF Power: 2 Wa;s RF max (per channel)
Port to Port Isola!on: 20 dB minimum
Repeater Tx to LF Inser!on Loss: 34 dB (VHF); 31 dB (UHF)
Repeater Tx to Surface Tx Loss: 13 dB (VHF); 15 dB (UHF)
Nominal Surface Tx Power: +20 dBm (VHF); +18 dBm (UHF)
Surface Rx to Repeater Rx Gain: -24 to +6 dB (VHF); -15 to +15 dB (UHF) (adjustable range 30 dB in 2 dB steps)
LF to Repeater Rx Gain: -35 to -5 dB (VHF); -27 to +3 dB (UHF) (adjustable range 30 dB in 2 dB steps)
Aux to LF Loss: 10 dB max
Number of Tx/Rx channels: 8 Tx, 8 Rx
LF Port Impedance: 75 ohms (N-Type Female)
Aux Surface Rx: 50 ohms (N-Type Female)
Auxiliary Band Frequency: 10 – 120 MHz (VHF); 10 – 250 MHz (UHF)
Repeater Tx to Rx Loss (@ Rx Freq.): >60 dB
All other Port Impedances: 50 ohms (BNC Female)
Alarm Outputs: Arterial voltage high /low; Arterial current high / low; 5 V DC TTL

Opera!ng Temperature: -20⁰C to +55⁰C (Ambient air)
Storage Temperature: -45⁰C to +60⁰C
Opera!ng Humidity: 10 – 85% non-condensing
Ven!la!on requirements / Airflow: Sealed case, no vents, no fans