Device for recording EM signals

[Horseb0x]

I'm looking for a device that can record EM signals of unknown frequencies (unknown to me) emitted by devices. For example if I point my remote control at it and start pressing buttons it should record intermittent IR frequency surges. Or for example if I build an emitter to modulate an encryption key into microwaves, this device should be able to record it and display it on an oscilloscope or something. I need a handheld device like this. What is this device called and how expensive are they?

[p1ayaone1]

You might be thinking of a device called a "spectrum analyzer". Good ones are very, very expensive. 6 figures is not unheard of. You might find a much cheaper on on ebay though.

A spectrum analyzer plots frequency on the horizontal axis, and the magnitude of frequency components on the vertical axis.

[skeptic2]

I doubt you'll find a sensor/detector that will respond to both IR and a broad range of radio wavelengths. Most likely you'll need to use a separate sensor/detector for each band that you want to detect. If your detector can convert the signal to base band, you could use an oscilloscope to observe the signal or a microcontroller to record the signal.

[cnidocyte]

6 digits, mother of god. Yeah I might try just hooking up an oscilloscope to a sensor.