Note
The Collins 180U-2 is a manually tuned antenna network, referred to as a "line flattener," designed to match a 50-ohm output from an RF amplifier to a 50-ohm transmission line. It is particularly effective for systems with a standing-wave ratio (VSWR) of up to 2:1, which it can reduce to 1.1:1 or less.
Core Components
Reversible L-Network: Used for impedance matching, this network includes a loading coil and variable loading capacitors.
Antenna Transfer Relay: This relay (K1) automatically connects the power amplifier to the directional coupler during transmission or the receiver during reception.
Directional Coupler & R-F Wattmeter: The unit includes a built-in R-F wattmeter (M1) that measures forward and reflected power. It features two selectable scales: 0-100 watts and 0-1000 watts.
Audio Monitoring: A 4-ohm loudspeaker is provided for audio monitoring, along with a 5-ohm terminating load that is automatically switched into the circuit when the speaker is turned off.
Output Selector: A switch (S3B) allows the operator to direct the signal to either the antenna or a dummy load.
Operational Features
The 180U-2 is designed for high-power HF communication systems, such as the Collins KWT-6. Its "Antenna Impedance" switch allows it to match antenna lines both above and below 50 ohms by reversing the L-network configuration. For tuning, it utilizes a combination of a variable loading coil and variable capacitors, which can be supplemented with additional 500 uuf or 1000 uuf parallel capacitance.
Specifications
Frequency Range: 2.0 to 30.0 MHz
R-F Power Input: 1000 watts PEP; 500 watts average maximum
Input Impedance: 50 ohms nominal, resistive, unbalanced
Output Impedance: 50 ohms nominal, unbalanced
Output VSWR: 2:1 maximum (reduced to 1.1:1 or less)
Wattmeter Ranges: 0-100 and 0-1000 watts (Forward and Reflected)
Power: :27.5 VDC at 125 ma (for antenna relay operation)
