Working on a multi-band QRP CW transceiver using Si5351A clock generator for VFO/BFO. Getting excellent frequency accuracy but seeing thermal drift of about 100Hz over first 10 minutes of operation. Using temperature compensation in software but curious what others have tried for hardware solutions.

Considering adding a small fan or heat sink to the Si5351 module. Has anyone tried mounting the clock generator remotely from the main board to isolate it from PA heat? Running about 5W output on 20/40m using IRF510 finals.

• Current drift: ~100Hz in 10 minutes
• Target: <20Hz drift for CW work
• Using Adafruit Si5351 breakout board

I mount my Si5351 on a separate small PCB with thick copper ground plane for thermal mass. Also added a small aluminum heat spreader - reduced drift to about 30Hz in the first few minutes. The key is keeping it away from the PA section.

Try implementing automatic frequency correction using a GPS disciplined reference. I built one using a NEO-8M GPS module that corrects the Si5351 every 30 seconds. Overkill for most applications but rock solid for weak signal work.

For QRP field use, I just let it warm up 5 minutes before making contacts. Simple solution that works - most ops understand if you need to "warm up the rig" at the start of an activation. Thermal mass helps too - I potted mine in thermal compound.