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Homebrew SWR meter for VHF, UHF and SHF (including Wifi ISM Band)

Homebrew SWR meter for VHF, UHF and SHF (including Wifi ISM Band)

The circuit on this page serves as a Voltage Standing Wave Ratio meter or VSWR meter for the VHF-UHF-SHF frequency range. This includes the Wifi (802.11b/g), 2m, 70cm and 13cm Radio Amateur bands.

When building antennes for the Wifi band (Like the 8dBi omni), a need for an easy way to check the antennas arrose. A Voltage Standing Wave Ratio (VSWR) meter useable at the 2,4GHz band is however, hard to find. Meters like the? Daiwa CN-801S are expensive and need a minimum of 500mW (27dBm) power to function correctly.

The device consists of two parts. One RF head and a (preferably analog) indicator. The meter has a 9 Volt alkaline battery power supply. The indicator on top is used to read the VSWR. The first switch is used to switch the power. A green low-current (2mA) LED illuminates when power is applied to the circuit.
The second switch is used to switch between slow (peak-hold) and Fast mode.

Below, the last control is the Sensitivity pot. It is used to adjust the meter sensitivity to the RF source used, such as a Wifi Access Point, or VFO. RF Input power must be somewhere between 15 and 20dBm (30 to 100mW)?

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