Bird - The RF Experts
8640B Series
8640B Series, 25 kW RF Terminations
8640B Series

25kW, Forced-Air Cooled Moduload™ RF Terminations

8640B Series, RF Loads are compact high-power 50-ohm loads that efficiently dissipate up to 25 kW of RF over a wide frequency range up to 1 GHz.

  • Interlock control circuit provides fail-safe protection of the transmitter and load resistor in the event of an ac power failure to the blower or coolant pump.
  • Compact, low-profile design saves space in crowded transmitter sites.
  • Available Voltage Options (add suffix to model number).
    • 115V @ 60 Hz (-115)
    • 230V @ 50 Hz (-230)
    • 230V @ 60 Hz (-230-6)
  • * Below 5°C, ONLY use 35% E.G. and 65% Dist. H2O mixture.
  • ** Above 30°C (86 °F) with water only, or 25°C (77 °F) with a 35% ethylene glycol mixture, derate power to 20 kW max.
Model Selections
Model Connector
8645B 3 1/8 in EIA, Flanged
8646B 3 1/8 in EIA, Unflanged


8640A930-1, Load Protection Switch provides an added layer of safety for the water-cooled Moduloads by preventing RF power from reaching it before proper coolant flow has been established. This device protects the Moduloads from damage that can result in costly downtime. Only Available for 8645B, 3 1/8 in Flanged Units

8640B Series, 25 kW RF Terminations
8640B Series
product specifications:
Item No
8640B Series
Item Name
25 kW, Forced-Air Cooled Terminations
Power Rating
25 kW continuous
** See note 2 above
Frequency Range and VSWR
1 kHz to 900 MHz @ 1.1 max (DC for continuity checks)
Temperture Range
Water Only: +5 to +45 °C (41 to 113 °F)
35% Ethylene Glycol: -20 to +35 °C (-4 to +95 °F)
** See note 2 above
Cooling Method: Water dielectric and forced air convection
Coolant: Distilled water or distilled water/ethylene glycol mixture
Coolant Capacity: 9 qts. (8.5 L) nominal
* See note 1 above
Product Type
Forced-Air Cooled
Operating Position
Horizontal Only
See Model Matrix
Gray Powder Coat
26 in x 19-5/8 in x 19-1/4 in (L x W x H) (67 mm0 x 500 mm x 490 mm)
155 lb (70 kg)
115 V models: 11 A nominal @ 115V ± 10% 60Hz
230 V models: 5-1/2 A nominal @ 230V ± 10% 50Hz
compatible devices:
3-1/8” Flanged Load Protection Switch
Ethylene Glycol, Industrial Grade