PTT for Yaesu FT‑891/FT‑857

Inline PTT for Yaesu FT‑891

This project describes how to build an inline Push‑to‑Talk (PTT) unit that integrates directly with a headset for field‑portable radio operation. The goal is to reduce the number of cables, adapters, and parts you need to carry—and potentially forget.

Overview

This inline PTT:

• Uses the existing Yaesu RJ45 microphone cable
• Is permanently attached to the headset
• Reduces external connectors and loose cables
• Provides an ergonomic 45° PTT button for comfortable operation

The headset used in this build is the KOSS SB‑40, chosen for its comfort and good microphone performance with Yaesu radios.

Components

3D‑Printed Parts

• Handle (houses cable and PTT button)
• Base (holds the RJ45 inline coupler)

Electronics & Connectors

• Momentary normally‑open push button (15 mm circumference)
• RJ45 inline coupler (  Amazon Link  )

• Width: 16 mm

• Height: 18 mm

• Length: 30.6 mm

• 3.5 mm stereo panel‑mount jack (6 mm thread) ( Amazon Link  )
• RJ45 ethernet patch cable segment (10 cm, uses only one connector) ( Amazon Link )
• Heat‑shrink tubing (2 mm, 10 cm total)

Tools

• 3D printer
• Wire stripper
• Precision flat‑head screwdriver
• Precision needle‑nose pliers
• Soldering iron and solder

Printing & Preparation

1. Print the handle and base upright for best finish.

2. Enable supports in your slicer.

3. Remove supports, deburr, and clean the printed parts.

Step 1 — Modify the Headset Cable

1. Cut the headset cable at arm’s length (about 100 cm).

2. Feed the cable through the handle until ~3 cm protrudes from the bottom.

3. Separate the internal cables into:
   • Speaker pair
   • Microphone pair
   • Ground/shield

Step 2 — Wire the Headset Speakers

1. Strip ~10 mm of insulation from each speaker wire.

2. Twist (“twissel”) and tin the exposed strands.

3. Tin the solder tabs on the 3.5 mm stereo jack.

4. Solder both speaker shield grounds to the longest solder tab.

5. Solder the remaining left and right signal wires to the two smaller tabs.

Step 3 — Prepare the RJ45 Cable

1. Insert the RJ45 inline coupler into the printed base and confirm orientation using the Yaesu mic cable.

2. Cut a 10 cm section of RJ45 cable including one connector.

3. Strip the outer sheath and shielding to expose the 8 internal wires.

Required RJ45 Wires

Due to differing color standards, confirm your pinout. Typically:

Microphone
• Pin 4 — Blue — Mic Negative
• Pin 5 — Blue/White — Mic Positive

PTT
• Pin 6 — Green — PTT
• Pin 7 — Brown/White — Chassis Ground

Step 4 — Solder the Microphone Wires

1. Strip and tin the microphone’s shield (copper) and signal (white) wires.

2. Strip ~5 mm from the microphone signal wire.

3. Cut two 15 mm pieces of 2 mm heat‑shrink and slide them onto the wires.

4. Solder:
   • Mic Negative → Pin 4 (Blue)
   • Mic Positive → Pin 5 (Blue/White)

5. Slide the heat‑shrink into place and shrink to insulate both joints.

Step 5 — Install and Wire the PTT Button

1. Feed the Green (Pin 6) and Brown/White (Pin 7) wires through the handle to the button opening.

2. Attach both wires to the screw terminals of the push button.

3. Pre‑twist wires by rotating the button counterclockwise 6–7 turns.

4. Thread the button into the handle with 6–7 clockwise turns.

Step 6 — Final Assembly

1. Seat the RJ45 inline coupler fully into the base.

2. Fit the base onto the handle.

3. Confirm:
   • Headset audio works
   • Microphone passes audio
   • PTT correctly keys the radio