If designing a new circuit, use these active MOSFETs:
Since the 3SK41 is discontinued, you have three options: 3sk41 datasheet
The 3SK41 is not pin-compatible with standard JFETs like the MPF102. The most common package is the 4-pin TO-72 metal can. Viewing from the bottom (leads facing you, tab pointing up): If designing a new circuit, use these active
Pinout Image Description (Text): Bottom view, tab at 12 o'clock. Pin 1 (Source) is clockwise from the tab. Pin 4 (Drain) is counter-clockwise from the tab. Pinout Image Description (Text) : Bottom view, tab
The 3SK41 was developed in the late 1970s and early 1980s by Japanese manufacturers like Hitachi, NEC, and Sanyo. It was famously used in the RF front-ends of high-end analog television tuners (Channels 1-12) and FM radio receivers.
Original equipment manufacturers (Hitachi, NEC) no longer host these files. However, you can find scanned, authentic copies at:
Pro Tip: When downloading, look for a document dated between 1985 and 1995. Later "generic" datasheets sometimes contain errors for this specific part.