Bird 8720 – Direct Water Cooled RF Termination (5 kW)

• Designed as a compact, low VSWR, and non-radiating termination
• Used with high-power transmitter/transmission line systems
• Power rating: 5 kW continuous
• Connector: 1-5/8 EIA, Flanged
• Small size may be carried easily, used in any position, and installed anywhere there is a source of potable water

The Bird 8720 Load Resistor is designed as a compact, low-reflection, and non-radiating termination of coaxial transmission lines. Cooled by internal water flow, it generates almost no ambient heat, making installation space minimal and convenient.

This sub-miniature unit may be carried easily and installed anywhere, for use in whatever position desired.

A Model 8720 can absorb up to 5000 Watts continuously and dissipate it harmlessly as heat over a frequency range of DC to 2000 MHz.

Power input is through a Bird 50 ohm 1-5/8 inch EIA flanged connector. The RF power is converted to heat in the load resistor, and directly dissipated by means of the water cooling system. Water flow through the inside of the resistor directly absorbs the dissipated power of the resistive film.

• Power Rating: 5kW Continuous
• VSWR:
• DC – 500 MHz @ 1.10 (max)
• 500 – 900 MHz @ 1.15 (max)
• 900 – 2000 MHz @ 1.25 (max)
• Impedance: 50 Ohms
• Water Rate & Temp.:
• 1 Gal.(min) | 4L (min) @ 5°C
• 4 Gal.(min) | 15L (min) @ 80°C
• Water Connection: 1/4 Tube to 1/4 F.P.T Coupling
• Connector: 1-5/8 EIA Flanged
• Coolant: Water-Cooled

The Model 8720 is a passive device that is self-contained and does not need any external source of power or utilities to function. It does need a source of running water, however, to provide for its cooling. The water must flow from a rate of one gallon (3.8 liter) per minute at a water temperature of +5°C (+41°F) to a rate of four gallons (15.2 liter per minute at +80°C (+176°F) in order to provide adequate heat dissipation.

The Model 8720 is equipped with a 1-5/8 inch EIA swivel flanged RF connector and 1/4 inch female pipe threaded nuts for the water supply lines. This operation manual is the only additional item furnished.

The only items required are a 1-5/8 inch EIA flanged coupling kit for the RF transmission line and 1/4 inch male pipe thread fittings on the ends of the water lines.