The following are tips and tricks to help you get the most out of your RF Nomad module.
======= Reception Tips ==========
Shortwave reception is a bit finicky by nature; radio waves travel around the world subject to atmospheric conditions, terrain, elevation, and surroundings. Here are some tips to help you get better reception.
1.) Time of Day. Atmospheric conditions vary throughout the day. Experiment with listening at different times of the day to see when is the best time of day for your location. Here in Pittsburgh, mid morning and late afternoon seem to work well. Folks in London have reported good results after midnight.
2.) Antenna. The supplied antenna is useful, but a longer antenna is always better. The included antenna is just a length of wire; if you strip the end of the wire and solder on a much longer piece of wire, reception will improve. Just be sure to insulate your solder joint with some tape or heat-shrink tubing, to protect against contact with live circuits.
3.) Elevation. The higher up you are, the better. If you are in a valley, or on the side of a hill, the local terrain may be blocking signals.
4.) Building materials. If you are inside a building, the metallic portions of the building materials may be blocking your signal. Try to run the antenna near an exterior wall, or out a window if possible. If you are in a basement, try moving to an upper story.
5.) Sunspots. Yes, the 11-year sunspot cycle affects radio wave propagation a great deal. During periods of low solar activity, the atmosphere is not very ionized, and radio waves do not reflect back down from the upper atmosphere as well. Sunspot activity also varies from one day to the next, so there may be better days than others.
You can "transmit" your own sounds to the RF Nomad using a second RF Nomad. ("Transmit" is in quotes, because the distance over which you can transmit is very small; see attached video): https://www.youtube.com/watch?v=e4taNHt7LWE
====== Tips on getting interesting sounds =========
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 plus carrier. 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! The limitations of the direct conversion receiver become an asset for us synthesists.
What's neat about the RF Nomad is that the tuning is 100% analog, and is voltage controlled. In fact, the "Tuning" knob on the front panel is just a potentiometer that applies voltage to the tuning circuit. The CV input allows a bipolar signal to raise or lower the tuning. In technical terms, there's a summing amp that adds the CV amount (plus or minus) to the Tuning amount.
The upshot of this is that 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 station -- it's awesome hearing what that does to broadcast voice stations.
Oh, yeah, something else --- because the RF Nomad is a direct conversion receiver instead of an AM receiver, if your tuning is off-frequency, the audio of the received station is shifted in frequency, too. Kind of like running the audio thru a ring modulator. So you can take your stately radio announcer and make him sound like a duck talking, just by tuning a little off-center.
The RF Nomad makes a great "colored noise" source. I don't know if you've had a chance to check the demos on my SoundCloud page, but check out http://www.soundcloud.com/rh2y for some demos of using the RF Nomad as a percussion noise source.
The Nomad tunes roughly 9.6 to 10.0 MHz, which is most active late afternoon to early evening, though your mileage may vary. 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.
Let's see.. am I forgetting anything? Oh, yes 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. But that makes actually *listening* to the radio a bit grating on the ears.
Fun fact -- 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. Or, patch the output to a filter, and then to a multiple and into the CV input, to take some of the noise out of the loop.
Also -- the Nomad's CV input is bipolar -- if you input a negative voltage, it will decrease tuning from the setpoint selected by the Tuning knob. If you input a positive voltage, it increases. However, there is a maximum and minimum tuning value that is attainable, so if you put the tuning knob all the way CCW, inputing a negative CV will not lower the tuning any further. Likewise on the high end. You can, however, use this to your advantage: This lets you "clip" the incoming CV signal -- if you input a pure sine on CV, but tuning is near one end of the range or the other, it clips to the max or min, and so, effectively, your CV is flattened on one side or the other. If the CV is a slow LFO, this makes for a neat repeating sequence with a pause in it! At audio rate CV, it sounds a bit wave-shapey.
Finally, because the Nomad is a direct-conversion receiver, warts and all, one of those warts is that it is slightly 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 just 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.
====== Modifying your RF Nomad for different frequencies ==========
There is a tradeoff between tuning range and the ability to pick out an individual station easily. SW stations are about 5 kilohertz wide. The RF Nomad tunes a range of about 9.6 to 10.0 MHz, or 400 kilohertz. Thus, there is the possibility of about 80 different stations on the dial, which rotates from about the 7:00 position to the 5:00 position. If the tuning range were any wider, it would be hard to zero in on any one station.
One thing to watch for is that if you are tuning the knob, if you hear a "pop", slowly turn the knob back towards that click. It may actually be a station, but you tuned past it quickly. Some patience is required.
The center frequency of reception is easily modded to a certain degree.
===>>>> CAUTION CAUTION CAUTION <<<<===
Be careful doing this while your modular is turned on!!! You could damage your modular, as well as the Nomad if you are not careful. You have been warned.
1.) Remove the RF Nomad from your rack, but leave it plugged in. Set the tuning knob to about the 12:00 position.
2.) DO NOT SHORT THE MODULE AGAINST ANYTHING WHILE POWERED UP!!!!
3.) See #2. Get a buddy to help, if you're not comfortable doing this.
4.) With a flat blade screwdriver (preferrably a non conductive screwdriver), GENTLY turn the slug inside the L5 inductor SLOWLY. It only turns about 1 full turn or so, but you are looking to make a SMALL adjustment.
5.) While turning, listen to see if you are now receiving more stations. L5 controls the center frequency of the tuning range. You can shift it up a little above 10 MHz by turning counter clockwise (this will receive the 30 meter ham band -- lots of morse code there). You can shift it downward a fair amount by turning clockwise.
6.) DO NOT force the tuning slug. They are pretty fragile. Turn slowly and gently. Once it starts to tighten up, you have gone as far as you should, and should go back a bit. You really shouldn't have to turn more than 1/4 turn in either direction to get where you need to be anyway.
7.) Button up your modular. Now you will have to wait about an hour or more for the tuning to "settle down". Turning the slug mechanically disturbs the circuit and it takes quite a while to settle down afterwards. You can use the RF Nomad right away, but you will notice a bit of tuning drift for quite some time after tuning L5. Be patient; it does settle back down after a fair amount of time.
I'm glad to see folks are enjoying the module; I understand it can be a bit frustrating trying to receive a signal at times. That is largely the nature of shortwave reception, unfortunately.
However, you should be able to get some interesting sounds even without a strong station, especially if you live in an electrically noisy environment. Try draping the antenna over various pieces of electronic equipment (avoid transmitters though -- stay away from things like cell phones, walkie-talkes, etc...) for interesting sources of sounds. My old fluorescent light fixture tends to make some neat heterodynes, and I'm anxious to go exploring the innards of my ZX81!
Update: Stuffing the antenna inside my old TRS-80 Color Computer indeed generates some interesting sounds!