Tuesday, November 25, 2014

Evaton Technologies RF Nomad Shortwave Radio Eurorack Module Demo by @MylarMelodies

MylarMelodies is known for his excellent Eurorack demos, you'll probably know him as the man behind the memorable Intellijel Metropolis demo (which is going towards 50.000 views already),the Vines that he posts from his Twitter account, and more recent, his writings for FutureMusic Magazine.

His latest demo is all about the Evaton Technologies RF Nomad Shortwave Radio, read all the info in the description below the video.

Video: RF Nomad Shortwave Radio Eurorack Module Demo

" Being a demo of the considerably bonkers shortwave radio eurorack module that is the Evaton Technologies RF Nomad. LOADS of additional information below!


"Get your antenna as high up as possible, and away from metal as much as possible. If you can clip a longer wire onto the end of it, to make the antenna longer, that will help too. I sometimes put a long wire on mine, and tape the wire up to the ceiling.

If you just can't pick up any signals with it, the tuning range is adjustable internally via tweaking the L5 inductor slug with a non-conductive screwdriver. If you are brave, power up your modular, with the Nomad hanging out of the case so you can get to the L5 inductor with a screwdriver. (Be careful not to let the module short against anything!) Set the Tuning knob to the center position, then tweak L5 until you hear stuff. Don't apply much force, and be aware that you can only turn the slug about 1 full rotation. Also, once you've done this, it's going to take a few hours (yes hours) for the tuning to quit drifting, because you've mechanically disturbed the inductor and it takes a while for it to stop creeping from the mechanical stress.


The RF Nomad started out as a germ of an idea between myself and my friend, DSP guru Michael Mecca of Pittsburgh Digital -- we frequently meet for lunch to discuss all things synth. About a year or so ago, he mentioned how much fun he used to have as a kid, playing with his dad's shortwave radio, making crazy squealy noises, listening to the haunting sounds that come over the airwaves. I said I had the same experience as a kid, too. Wouldn't it be cool to make a module that lets you bring that experience into the modular world?

I actually had plenty of experience with radio circuits, and a rudimentary design for a shortwave receiver with voltage-controlled tuning immediately sprang to mind.

Most off the shelf shortwave receivers are AM (amplitude modulation) receivers, which suppress the carrier signal. From my ham radio experience, though, I know that if you listen to shortwave frequencies with a sideband decoder instead of an AM decoder, you hear the carrier signal as well as the audio signal, which I feel is far more interesting as a sound source for a synth than just the plain audio alone. It's the bit that gives you those searing heterodyne squeals.

So, it was decided to go with a "direct-conversion" receiver design, which receives both sidebands. Normally, one doesn't think of a direct conversion receiver when trying to design a modern receiver, because they are very crude. But, in the case of the RF Nomad, crude is exactly what we want! It's gives more squeals, more hiss, more heterodynes, more brutal nasty sonic goodness!

You can alter the tuning with the CV input, like it's a remote control for the tuning knob. Apply an LFO, and the tuning slowly increases and decreases. Attach it to a sequencer, and you can cycle thru stations, or just cycle thru different pitches of squealy heterodynes. Hook it to an envelope generator and get on-demand heterodyne swoops. Hook it to an audio-rate LFO, and now you get freaky FM effects. Really cool if you happen to be receiving a strong broadcast station.

The Nomad tunes roughly 9.6 to 10.0 MHz, which is most active late afternoon to early evening, though YMMV. If you can't get a strong station, you can try extending the antenna (just clip another length of wire onto the end of the supplied antenna). Or, find some old electronics, and drape the antenna over it. Stuff from the 80s/90s era -- Commodore 64's, PC AT's, game consoles, etc. The EMI generated by these devices makes for some interesting sonic material.

If you do want to simply "listen" to shortwave on the Nomad, you'll want a bandpass filter after it. The output is 100% UN-filtered, to allow you to have plenty of material to feed your favorite filters with.

The output of the Nomad can be fed back into it's CV input for some self-modulation fun. Patch the output to a multiple, and then feed one signal from the multiple back into the CV input.

Because the Nomad is a direct-conversion receiver, warts and all, one of those warts is that it is somewhat drifty with temperature. I've done about as much as I can to reduce the driftiness, but you will notice that over several minutes it will wander around a little bit. I felt this was an acceptable trade-off, as the true talent of the Nomad is how well it responds to a quickly changing CV input to generate quirky sounds.

I think that covers the basics. It's pretty versatile for a module that only has one input."