If you absolutely need XPSpeak41 specifically (e.g., a niche mode it supports), ask on or Reddit r/RTLSDR – someone may have a clean copy and can share a SHA-256 hash.

Evaluate the residual line (the difference between the raw data and the total fitted curve). A flat residual line indicates an accurate fit.

If users find the 16-bit interface of XPSPEAK41 too dated, consider mentioning these more modern, free alternatives found in ResearchGate discussions: KherveFitting