Note
Ham Radio, Jun 1973, p. 56.
The Bird model 4372 Thruline directional wattmeter covers 25 to 500 MHz from 1 watt full scale to 500 watts full scale without changing plug-in elements. This flexibility is accomplished by eight easily switched ranges: Four forward power levels (10-500 watts) and four reflected power values (1-50 watts). The lower reflected power ranges are also available for forward readings by reversing RF connections.
In operation, a precision machined 50-ohm reference line-section is inserted
between the signal source and the antenna, load or other component under power test. Directional power sensors incorporated in this line-section produce DC signals proportional to both incident and reflected RF main-line power, for readout on scales calibrated in watts as well as dB.
All variable measurement parameters–frequency range, forward/reflected power and full scale values–are switched from on the front panel. The read-out unit and the line-section may be separated by as much as 3 feet for operational convenlence.
The new multi-range model 4372 is ideal for CW, AM, FM, SSB and TV signals, for design and maintenance of oscillators, transmitters and transceivers, for antenna matching, and design and development of RF components such as filters, sensors, loads and power transistors.
It requires neither AC or battery power.
Measurement accuracy is ±5% on all ranges from 0-1 watt to 0-500 watts at
25-500 MHz, and fits standard 19-inch racks. Requires 5 1/4" of rack space.
References
Brief description. Ham Radio, Jun 1973, p. 56.