SWR power meter

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Frequency Range 1-150 MHz
Power ranges 3W, 10W, 30W, 100W, 300W, 1kW
Size 70mm(H) 130mm(W) 40mm(D)
DC Power 9V PP3 (which lasts for ages)

This SWR power meter uses a Bruene bridge directional-coupler and a compensated operational amplifier to provide high-accuracy power measurements, even at very low power levels. Matched OA47 Germanium diodes are used in the Forward and Reflected detectors and the feedback-loop of the op-amp, which compensates for the non-linearity of the detector diodes.

A battery-switch circuit turns on automatically when about 1W of RF is sensed and stays on for 5 seconds after a transmission.

Forward-power metering has a 1 second time-constant peak-hang circuit to indicate true PEP. Reflected-power metering has a 10ms time constant which is a help when dipping the reflected power with an ATU. The Power meter has been extensively tested with a wide range of transceivers and linear amplifiers and works very well.
Click on a thumbnail below to see a larger picture

Return loss measurements, 1 to 150MHz

Transmitter input side, with the Forward/ Reflected switch.

and moving round,

past the operator's view,

to the,

antenna output side, with the battery test switch.

Inside, two boards. The bottom board is the directional coupler and power-on sensor. The top board is the op-amp and meter-drive circuit

Close-up view of the meter scale

unique visits since Nov 2005