I had W4RT perform the installation of their One Big Punch in my Yaesu MH-31 microphone used with my Yaesu FT-857D transceiver ...
W4RT Electronics warrantee on its products (OPP-xxx, OBP, OBF, OPF, Antenna BOSS & BOSS II, etc.) is typically one year, except on battery packs, which is ninety days. Specific terms are presented in the product instruction manual. W4RT Electronics does not (i) sell used products nor (ii) have any provisions for customers to "try product out for evaluation."
OBP Installation and User's Manual -- Check your FT-857D menu setups.http://www.w4rt.com/Manuals/OBP_manual.pdf
How the W4RT One Big Punch (OBP) works.http://www.w4rt.com/FT-817-Accessories/OBP_tech.htmOne BIG Punch (OBP) is a custom add-on accessory for the Yaesu MH-31 microphone that is used with the FT-817(ND), FT-847, FT-857(D), and FT-897(D). The OBP is an AF-based speech compressor specifically configured to provide remarkable increase in talk power while maintaining good audio quality (articulation) for communication purposes.