OM1EPT Voice Keyer, Part 1 - Idea

What is an voice keyer?

Good question, it is basically the same thing as a normal CW keyer, just for audio. So you just record yourself calling CQ, for example, and then just hit a key or a button, and it will play that audio for you. This can be particulary usefull in contests, when the conditions aren’t perfect, and there are no stations calling you. Or, in my case, I wanted a voice keyer I can use at WWFF (WorldWide Flora Fauna) activations. It usually takes me an hour to activate one flora fauna spot - and constantly calling “CQ FLORA FAUNA, CQ FLORA FAUNA….” can be, well, annoying for the people around you, that came to enjoy silence, and insted are forced to listen to me doing my nerdy activities. So I want to build a super portable, NOT MICROCONTROLLER BASED, simple voicekeyer device I can just put between my microphone and the radio, with only one aditional cable required.

What shall it look like?

I want the device, as I already mentioned, to be as smallest as possible, but still use through hole components for easy assembly and repairability. I also want it to sit between the microphone and the radio: I plug the microphone into the keyer, and then the keyer into the radio’s microphone RJ45 port. That port also provides +5V supply, so I don’t have to worry about batteries. The device should be simple to operate and provide decent enough audio and it should not use a microcontroller. Why? It is not that I hate MCUs, in fact, I very much like the idea of me able to add aditional functionality to my projects without completelly redoing the thing. It is that this device should serve one simple purpouse. And it also should be simple to build and operate. So no waiting for the MCU to start up, no need to program it when you want to build it, because there are dedicaded ICs designed specifically for this purpouse.

ISD2590p

ISD2590p is the heart of this project, that I am planning to use. It is a integrated circuit, that provides 90 seconds of memory, which is plenty for my purpouses. It also provides a sample rate of 5.3kHz and a filter for 2.3kHz, which is conviniently the width of our SSB signal, here in R1 (I didn’t, yet, order the IC, so I cannot evaluate the sound quality, but the IC check’s all my points (we will discuss more of them later), that I want for the voice keyer to obey, so the sound quality is the deciding factor, if I am going to use it or not). It can also be controlled with 2 simple buttons and one toggleswitch. One button for pause/play, one for stop/reset and a toggle switch for switching between recording or playback, which is just enough to provide all the fuctions I need, but also keeps the user interface simple :)

Audio switching

to be continued :>