6400 Lower Output and Higher PA Temp on 10 & 12m

From Chat GPT for what it's worth:

The FlexRadio 6400 (and 6400M) uses the same RF deck design as the 6600, with a single 100 W power amplifier module.

The power amplifier transistors (modern LDMOS devices, e.g., NXP/Freescale MRFE6VP61K25H or similar) are designed to safely operate up to ~150 °C junction temperature. However, FlexRadio manages them well below that limit.

Typical ranges you’ll see in normal operation:

• Idle / receive: ~30–40 °C (depends on ambient temp and airflow)
• Transmit, light duty (SSB, CW): ~50–65 °C
• Transmit, heavy duty (RTTY, FT8, digital, high duty cycle): ~65–75 °C
• Maximum safe operating range (before protective shutdown): ~85–90 °C reported at the device flange

FlexRadio firmware will automatically reduce output or shut down the PA if temperatures approach unsafe limits. In practice, most operators report PA temps in the 55–70 °C range during normal use, even with digital modes at 100 W continuous.

👉 If you’re seeing >80 °C often, it’s worth checking:

• Dust buildup on the heat sink or fans
• Adequate airflow around the radio (not enclosed tightly)
• Fan operation (the internal fan ramps with temperature)