The Diamond SX-400 SWR/Power Meter is an essential tool for amateur radio enthusiasts operating within the VHF and UHF frequency bands. Designed to provide precise measurements of forward and reflected power, as well as Standing Wave Ratio (SWR), this compact device ensures optimal performance of your radio equipment.

Frequency Coverage and Power Measurement

Operating over a broad frequency range of 140 to 525 MHz, the SX-400 is suitable for a variety of applications across both VHF and UHF bands. It offers three selectable power ranges—5W, 20W, and 200W—allowing for accurate readings tailored to your specific transmission power requirements. The meter's accuracy at full scale is specified as ±10% for the 5W range, ±5% for the 20W range, and ±5% for the 200W range, ensuring reliable data across all settings. 

Measurement Capabilities

The SX-400 measures forward RF power, reflected RF power, and SWR, providing comprehensive insights into your antenna system's performance. It features both Average (RMS) and Peak Envelope Power (PEP) measurement modes, enabling users to monitor real-time power levels accurately. The minimum power required for SWR measurement is 4 watts, making it suitable for various transmission scenarios. 

Design and Build

Constructed with user convenience in mind, the SX-400 boasts a compact design with dimensions of 155 mm in width, 63 mm in height, and 103 mm in depth, and a weight of approximately 540 grams. This makes it ideal for both base station setups and mobile installations where space is at a premium. The meter is equipped with SO-239 connectors, ensuring compatibility with standard coaxial cables used in amateur radio setups. 

Insertion Loss and Accuracy

Maintaining signal integrity is crucial, and the SX-400 excels in this aspect with minimal insertion loss. It exhibits an insertion loss of less than 0.1 dB in the 140 to 250 MHz range, less than 0.2 dB between 400 to 470 MHz, and less than 0.3 dB at 525 MHz. This ensures that the meter's presence in the transmission line does not adversely affect your system's performance. 

Illumination and Power Requirements

For ease of use in various lighting conditions, the SX-400 features an illuminated meter display. This illumination requires an external 12 V DC power source, ensuring clear readability of measurements even in low-light environments. 

Key Specifications:

• Frequency Range: 140 to 525 MHz

• Power Ranges: 5W, 20W, 200W

• Accuracy at Full Scale:

• 5W Range: ±10%

• 20W Range: ±5%

• 200W Range: ±5%

• Minimum Power for SWR Measurement: 4W

• Insertion Loss:

• 140-250 MHz: <0.1 dB

• 400-470 MHz: <0.2 dB

• 525 MHz: <0.3 dB

• Connectors: SO-239

• Dimensions: 155 mm (W) x 63 mm (H) x 103 mm (D)

• Weight: 540 grams

• Display Illumination: Requires external 12 V DC power

In summary, the Diamond SX-400 SWR/Power Meter combines precision, versatility, and user-friendly design, making it an indispensable instrument for monitoring and optimizing your VHF/UHF radio systems.

Note: For additional information, look at the files under the "Documentation" tab.