FT-101 Audio Modifications

by Bob - N1UJS

These mods worked beautifully on my FT-101E. They came to me from Eric, WB2CAU, who got them from Mark, WA1FAF who got them from the Master himself WA1HLR. Seventy-three and I hope these are a help to many.

Transmit Modifications


  • Change R2 from 47k to 4.7 M for crystal mic (D-104, etc.)
  • Add 100 pF in parallel with R2 to bypass RF.
  • Change C2 from 10 uF to 150 uF.
  • Change R3 from 4.7k to 1.5k.
  • Change C5 from 1 uF to 10 uF.
  • Change C3 from 0.047 uF to 0.001 uF disc ceramic.
  • Change C7 from 1 uF to 10 uF.
  • Change C8 from 22 uF to 150 uF.
  • Change C9 from 0.01 uF to 0.001 uF.
  • Change C11 from 2.2 uF to 22 uF/35V .


  • Change C12 from 0.22 uF to 2.2 uF (+ towards R7/8/9 )(use C11 removed from PB-1315).
  • Change C2 from 0.01 uF to 0.001 uF.
  • For high level auxilliary input from tape deck or other source cut L36 from pin 5 and connect to pin 4 of PB-1315 board.

    Receive Modifications

    First and foremost, the narrow SSB IF filter makes signals through the receiver sound very muffled. Fortunately, there is an aftermarket 6 kHz wide AM filter available for the FT-101/B/E/F series from:

    International Radio and Computer, Inc.
    3804 South U.S. 1 Fort Pierce, FL 34982
    Phone: (407) 489-0956, FAX: (407) 464-6386

    The filter is the Fox-Tango #2011. Price as of January 1993 is $75.00 plus shipping. The filter is installed in place of the CW filter, with some minor circuit changes so that the 6kHz filter is in circuit when the mode switch is placed in the AM position. The SSB filter remains in the FT-101 and is used in the SSB and CW modes.

    ** If you buy a used filter without the instructions, refer to Yaesu FT-101 series Maintenance Service Manual (Yaesu part # 50900) available from Yaesu for installation instructions.


  • Change C45-from 0.1 uF to 10 uF/25V electrolytic (+ towards base of Q9).
  • Remove C39 0.047 uF.
  • Change C43 from 0.01 uF to 10 uF/25V electrolytic (+ towards Q9).
  • Change C44 from 220 uF to 750-1000 uF at 10V.
  • Change C40 from 33 uF to 150 uF.

    For further information on the FT-101 refer the The Yaesu FT-101 HF Transceiver Home Page by NW2M.

    Back to the Mods Page

    15 February 1999