PICAXE-08M Standalone Automatic Voice Keyer

After using a voice keyer in various contests and activations on my Icom IC-756pro3 I really found I missed one on my Icom IC-910H VHF/UHF transceiver.  There are commercial hardware solutions (like the MFJ-434B) and some software ones about but I don’t do commercial if I can help it 🙂
I’d previously been introduced to a Winbond voice recorder chip some time back but this has since gone obsolete so I needed to find another.  After doing a quick Google I found a webpage run by Quasar Electronics and they have a good selection of voice modules available.


At first I bought a couple of the 30A63 modules at £12.95 each, these are a 20 second single message assembled PCB kits which are very simple.  I designed up the PICAXE-08M controller so it would automate it and all was working but unfortunately the playback quality is not very good, there seems to be what sounds like the digital sampling clock in the background of all the played samples.  The audio was well above this noise but I still wasn’t happy with it. Also it used differential inputs and outputs which just made the integration with a radio a little more tricky.  These modules are quite good value and they will get used elsewhere where they are more suitable.



I then went back to Quasar Electronics and looks at the other options and decided on and bought the 3189 kit which is a 120 second multi-message sound recorder module for £29.95. This has several advantages over the 30A63. It has 4 memories (this project only uses 1), it supports a better sampling rate and can be run from 12v, it has a 5v regulator onboard and it has line in and line out options so I could record a message from the radio and play it back.  The line out option makes interfacing to the data port on the IC-910H much easier, only an isolation transformer and variable resistor, for levelling, are required.  After removing the original voice module from the project box the new one fitted in it’s place nicely and almost all the original wires used for start, stop, record and active went on as before.  I say almost as before when the 30A63 module was playing it would have a playback line which went high to light the LED which I also used to drive the PTT transistor.  The 3189, although each button has pads for connecting external switches, flashes the LED during playback – not so good.  After bringing up the datasheet on the Winbond ISD17120 recorder IC I noticed pin27 was used for INT/RDY (interrupt/ready) which during playback goes to ground. The 3189 PCB had no provision for this pin so I had to solder a wire to the PCB pad directly on the bottom side of the PCB.  I now have this driving a relay and the external PTT is over the contacts of the relay (not shown in the schematic).





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