Evaton Technologies AModulator - DIY Build
The Evaton Technologies AModulator SDIY kit is a companion module to the RF Nomad voltage-controlled shortwave receiver. What does that mean though?
In crude form the AModulator is a RF amplitude modulator that produces a micro-power radio-frequency signal which the RF Nomad can decode.
Still not making sense? It’s ok, it didn’t make sense to us until we dove a little more into this sidecar module.
Simply put, the AModulator allows you to encode any audio signal into an amplitude modulated RF signal, which the RF Nomad can then decode back to audio, with all the artifacts of vintage shortwave sound.
The AModulator SDIY kit consists of two printed circuit boards and thru hole components required to complete the kit. One circuit board contains the actual electronics of the module, and the other circuit board serves as both the faceplate of the module, as well as a touch-plate antenna.
How does it work?...
The AModulator is a very simple RF oscillator that employs amplitude modulation to vary the amplitude, or “volume” of a radio-frequency signal. The amount of amplitude modulation is directly controlled by the amplitude of an audio signal that is input through a front-panel jack on the AModulator.
In short, the AModulator puts those classic squelchy, squealing, hissy sounds of a shortwave radio into your modular, via reception on an RF Nomad! You can even use your own audio program source to create material to mangle with your RF Nomad.
Let’s get on with the build!
D1 and D2 are 1N4001 thru-hole diodes. Carefully bend the leads on the diodes, and insert them into the PCB, making sure the silver band on the diode lines up with the white line on the PCB silkscreen. It helps to bend the leads backwards a little bit before soldering them on the back side of the PCB. After soldering, clip off the excess component leads.
Electro capacitors are next up and the main thing you want to keep in mind is that polarity counts. Make sure you put the long leg of the cap into the square hole on the PCB. The white line on the cap should line up to the silkscreen on the PCB too. After placing these in their rightful place, flip the board over and tack them down. While you are here, place the transistors in U1 and Q1 and then tack everything down as well.
Ceramic capacitors, power header and a few resistors are the only things that are left on the backside of the board. Oh wait, we can’t forget about the 9.8304MHz TTL Oscillator Module (the square silver component).
After placing the resistors in whatever way you would like (polarity doesn’t matter), place the ceramic capacitors alongside them. Then, flip the board over and solder everything into place. Don’t forget about the 10-pin power header pins, making sure they sit flush on the PCB prior to soldering. (take note of the -12/1pin location).
The 9.8304 MHz TTL Oscillator Module
The Oscillator module has a very specific mounting position. In one corner, you will see a small dot on the top of the part. Use a magnifying lens if you have trouble seeing it. There is a corresponding dot on the silkscreen via the PCB. Line these up, flip the board over and complete the tack down process. Now, we are done with this side fo the board… time to move to the control side.
AModulator - Time Lapse Build
Evaton Technologies AModulator Build Gallery
The Control Side
When you flip the PCB over you should see spots for the 3.5mm jack, a switch, the potentiometer and a trimmer pot. Place all of these parts in their homes, but do not solder anything just yet. We will line things up with the touch plate panel before we complete the soldering.
Now, cut a 2 inch or so length of 22AWG or smaller wire, and strip about 3 millimeters off each end. Solder one end to the rectangular solder pad on the back side of the faceplate PCB, with the wire tailing away. Insert the other end of the wire into the backside of the PCB with the jack, pots, and switch, into the hole marked “TP1”. (This marking is on the opposite side of the board). You will be inserting the wire through from the back of the board, and soldering it on the side with all the electronic components (refer to photos if you need to).
Final Assembly…
After you have soldered the wire to both of the boards, it is now time to mate them. Gently lower the touch plate board onto the controls of the PCB. Line things up and make sure the wire you just soldered doesn’t get pinched.
Once everything is lined up, place the nuts on the pot, switch and jack. Hand tighten only. At this point, you can flip the board over and complete the soldering of the pot, jack and switch on the back of the PCB. We used our Synth DIY Toolset to complete tightening down the nuts on the touch plate board.
Knob time…
The knob provided with the Evaton Technologies AModulator matches that of its kin the NOMAD. All you need to do is place the blue tab on the top of the knob and press it down into the top knob hole. Next, twist the Audio Gain potentiometer on the AModulator fully counter-clockwise. Install the knob so that the white line is pointing to roughly the 7- o’clock position and then push the knob on. Make sure its not pushed so far that it binds against the pot nut. If they do, gently pull the knob back up (or pry with a plastic object, so you don’t scratch the faceplate.
Pat yourself on the back, you have just completed the Evaton Technologies AModulator. Time for calibration and patching. According to the build documents, fine tuning is pretty easy.
Calibration
Switch on the AModulator making sure you also have an antenna plugged into your RF Nomad. Slowly turn the tuning knob on your RF Nomad until you hear a strong heterodyne squeal. To make sure it’s your AModulator you are hearing, switch off the AModulator. If the squeal stops, you’ve tuned into the AModulator! Switch the AModulator back on. Next, plug a mono audio cable into the input of the AModulator. Turn the Audio Gain knob up about halfway or more, and adjust the volume of whatever device you are using to supply the audio signal.
Tune the RF Nomad carefully until you hear the heterodyne frequency drop to nearly zero. Now you should be able to at least faintly hear the output of the AModulator. Poke a small Philips screwdriver through the hole in the faceplate on the AModulator, and adjust the bias trim potentiometer carefully to get the best sound. You may have to experiment a bit with antenna placement to get the best signal also. If you are having difficulty, leave the bias trim approximately at the
Patching Ideas
Although the simplest patch is to run audio from something like an MP3 player or another Eurorack module into the audio jack, and use the RF Nomad to mangle that audio, there are some other interesting possibilities to explore.
Try patching the audio output of the RF Nomad into a mult, and run a copy of the RF Nomad’s audio output signal into the audio input jack on the AModulator. Now you’ve got a feedback loop that has an RF component to it that you can “play” with the touch plate!
Weirder still, patch another copy of that signal in to the CV Input jack on the RF Nomad! Crazy feedback fun!
AModulator Final Thoughts...
We bought this module for one reason and one reason only; to get some use out of our RF Nomad module. Since receiving the Nomad module, we haven’t been able to do much with it due to our studio location and having very thick walls. We even purchased the extended antennae and have had little to no luck in receiving a solid signal to mangle.
The AModulator allowed us to bring new life into the Nomad to say the least by allowing us to modulate a signal through it. For this reason alone, we recommend picking up one of these companion modules if you are having any sort of reception issues with the Nomad. In the end, we look forward to spending more time with these modules and seeing what they can do not only alone but together as well.
Curious where to buy the AModulator module by Evaton Technologies? If you are located or around the the UK, hit up THONK for a DIY Kit. For stateside purchasing, go see our friends at Synthcube to pick up your kit.
If you have questions about the build process or suggestions/feedback about this article, feel free to let us know by contacting us We look forward to hearing from you!
Until the next build …
