BX-184 Voice Keyer

The BX-184 is a voice keyer developed by Olli DH8BQA designed to fit into the case of a Yaesu MH-31 microphone.  I used the BX-184 at the G3PYE contest station before upgrading to an FA-SM Station Manager.


BX-184 Features

Even though the BX-184 is designed to fit into a Yaesu mic case it’s not limited to Yaesu radios.  DH8BQA designed in a set of jumpers between the RJ-45 mic/radio connector and the BX-184 circuit meaning the RJ-45 connector pins can be wired in any order.

To control the voice keyer function, the heart of which is an ISD1760 voice recorder chip, DH8BQA has a PIC controlled from a single push button, the FAST button on the MH-31.

This push button is used to control all aspects of the voice keyer;

  • Record mode
  • Single voice playback
  • Repeat voice playback
  • Repeat interval delay

Boxing the BX-184

I didn’t plan to put the BX-184 into an MH-31 case but instead planned to mount it in an ABS box.

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On the back panel I cut a hole to match the position of the RJ-45 connector and fitted a phono connector for PTT in and a 3.5mm socket for microphone in.

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On the front I fitted a button to be used for the voice keyer control and an LED to show when the PTT was active.

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The finished boxed BX-184 worked really well and really helped us, G3PYE, in contesting.  Before using the BX-184 we used a PC based voice keyer by SM3WMV but there were 2 disadvantages of this; first it needed the data interface to be connected adding complexity to the setup (levels, connections etc)and secondly using the data interface on the radio meant the voice keyer audio from the PC was not passing through the compressor of the radio.

The only flaw we found with the BX-184 is the push duration between enabling auto mode in the voice keyer and putting it into record mode was not very different so many users accidentally erased the voice recording instead of putting it into auto mode.

After finishing the boxing the obligatory labelling was done.

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  1. Rien

    Dear Gavin , At what point is the red wire from the led connectected . I use a digitast swith for the fast and ptt switch . it works very well. 73 Rien PE1MAI

    1. m1bxf (Post author)

      Hi Rein, I don’t have the unit here but the LED was a 5v LED as we connected between pin 2 of U2 (pin 2) and ground.


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