VSWR Bridge Tx/Rx Switch Module 1.8 – 54 MHz 160-6M SWR Power Meter 100W for Ham Radio SW Shortwave Amplifier, SSB AM CW FM

Part Number: RBS-RF603

The presented circuit module is a Voltage Standing Wave Ratio (VSWR) bridge & Transmit/Receive (Tx/Rx) Switch and is developed for short wave (SW), in other words high frequency (HF) applications. The VSWR bridge module can operate in the frequency range of 1.8 – 54 Mhz. Thus, this VSWR bridge module is suitable for use in amateur (HAM) radio bands from 160 meters to 6 meters. In HAM radio applications, it works compatible with SSB, CW, AM and FM modulation.

The presented VSWR module is suitable for up to 100W RF power. This module should be employed by connecting it to the output of the RF power amplifiers which has output filter or switchable low pass filter (LPF) modules. Thus, the forward-reflected RF powers and VSWR at any RF amplifier or transceiver output can be measured instantly and accurately by this module. At the same time, this circuit module has a Tx/Rx switch function triggered by Push-to-Talk (PTT). In this way, the signal line can be set as receiver or transmitter via relays, depending on the mode of the transceiver.

The module size is minimized by using miniature relays and is designed in a compact structure with SMA inputs and outputs. This VSWR bridge module is compatible with our HF power amplifier module and 7 band LPF module.

Highlights

- Compact design,

- Compatible with amateur radio bands (160, 80/75, 60, 40, 30, 20, 17, 15, 12, 10 and 6 meters bands),

- Accurate meter outputs,

- Internal Tx/Rx switch,

- SMA connector for inputs and outputs.

Technical Specifications

- Supply voltage: 11-15 Vdc (max), nominal 13.8 Vdc,

- Current consumption: max 50 mA,

- Frequency band: HF, beginning of VHF (1.8 – 54 Mhz),

- Wave length: 160 – 6 Meters,

- RF power: max 100W,

- Inputs impedance: 50 ohms,

- Outputs impedance: 50 ohms,

- Power Meter outputs: 0-5V (non-linear),

- Accuarcy: ±5% in 1.8 – 54 Mhz frequency band*,

- PTT input level: 3.3/5V compatible (High for TX, Low for RX) max 15V,

- Dimensions: 69 x 43 x 1.6 mm for PCB, 69 x 51 x 20 mm for module.

*Note: This is valid when the module is connected to after the LPF filter output. Due to harmonics at the RF output of unfiltered amplifiers, the error in power measurement increases depending on the power.

The blog diagram of the module is shared in photo section. When the PTT input on the module is triggered, the RF amplifier connected to the transceiver is activated as a transmitter in the power path. In this process, the forward and reflected power separately give the power meter signal output proportionally between 0-5V. The power and VSWR values can be calculated thanks to these signal amplitudes. When the PTT trigger is cut off, the RF amplifier is disabled from power path, thus the transceiver output is routed to the antenna and the module goes into transmitter mode.

Pinouts

SMA Inputs/Outputs*:

XCVR (Input): Connecting transreceiver output,

AMP IN (Output): Connecting RF amplifier input,

AMP OUT (Input): Connecting RF amplifier output,

ANT/Load (Output): Connecting antenna or dummy load.

CFB pin group**:

Pin 1: Supply input (11-15 Vdc),

Pin 2: NC (not connected),

Pin 3: PTT input***,

Pin 4: Forward power meter output,

Pin 5: Reflected power meter output,

Pin 6: GND.

*Note: SMA connectors are indicated in parentheses next to their names as input or output.

**Note: CFB pin group is used to control Tx/Rx switch and measure power meter signals. The power meter signal comes from two separate pin outputs as forward and reflected power. Power meter signal amplitudes can be measured with a multimeter or a microcontroller, then RF power and SWR values can be calculated with the conversion equations (given in the instruction section).

***Note: PTT input is compatible with 3.3/5V logic. Maximum trigger signal level is 15V. Between 0-1V input signal should be used for LOW state, between 2.4-15V input signal should be used for HIGH state. When PTT pin is HIGH, Tx/Rx switch is set as transmitter. When this pin is LOW, Tx/Rx switch is set as receiver. When there is no connection to PTT pin, T/R switch is internally in LOW state. In this case, Tx/Rx switch works in receiver mode.

Application Instructions

The following equations are used for the calculation of forward power, reflected power and SWR value. In these equations, P_fwd is the transmitted power, P_rfl is the reflected power, V_fwd is the forward signal amplitude measured from the pin and V_rfl is the reflected signal amplitude measured from the pin. Vswr is the standing-wave-ratio value.

(1) P_fwd = 2 * (V_fwd * 1.54 + 0.05) ^ 2

(2) P_rfl = 2 * (V_rfl * 1.54 + 0.05) ^ 2

(3) Vswr = (1 + V_rfl / V_fwd) / (1 - V_rfl / V_fwd)

Tips

(1) Inputs and outputs are compatible with 50 ohms.

(2) There is no reverse power protection on the circuit. Please check the supply polarity first when connecting the power.

(3) ANT/Load output must be connected to a 50 ohm antenna or load.

(4) Before operating the module, first check whether the SMA connections are made properly.

(5) The Tx/Rx switch function determines whether the module works as a receiver or transmitter.

(6) The PTT output of the transceiver should be connected to the PTT input of the VSWR module.

(7) When the PTT input is triggered (HIGH status), the RF power amplifier is activated and the module switched to transmitter mode.

(8) After the trigger is cut off (LOW status), the RF amplifier is disabled and the antenna is directly connected to the transceiver via relays. This mode is the receiver mode.

(9) The PTT input is internally in the LOW state. If this pin is not connected, the Tx/Rx switch is in the receiver mode.

(10) The forward and reflected power signals can be measured via two separate pins. Power and VSWR values can be calculated with the conversion equations.

(11) This VSWR bridge module does not support Peak-Envelop-Power (PEP) for power measurement.

(12) For a proper power and SWR measurement, the module should be connected after a filtered amplifier or low pass filter modules.

(13) In a power transmission line that is not clean in terms of harmonics, serious deviations may occur in instantaneous power and SWR measurements.

Package Included

- VSWR bridge module

- Control cable (6 pins, 2.54 mm and 20 cm long with connectors)

Typical Connection