Is it even possible?

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joeyblack

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This may be a very dumb question, but I'll let you know before I ask it that I have no knowledge of how radio frequency works. My question is is it possible to make a device that can detect radio transmissions across all frequencies? Would something like this be very complicated and expensive? If something like this is possible could someone please give me an idea as to where to look for information on how to complete this task?

Thanks in advance for any help.
 

RKG

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Yes.

Two classes of devices. A "spectrum analyzer" views a slice (which can be pretty wide) simultaneously, and will show spikes where there is RF energy. A central part of a good service monitor and quite expensive. A "sweep receiver" will sweep across a designated slice very quickly, latching onto any decodable signals. Dirt cheap but only works for signals generated quite close (i.e., no sensitivity).
 

kb2vxa

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If all you want to do is detect RF you can build a simple field strength meter out of a handful of junk box parts, not across ALL frequencies but good enough for government work. On the other hand a frequency analyzer that can "see behind the veil" into the GHz region will cost you a few 10K bux and considerable study to use it.

Where to look and for what is a use specific matter, you haven't specified your use.
 

benbenrf

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This may be a very dumb question, but I'll let you know before I ask it that I have no knowledge of how radio frequency works. My question is is it possible to make a device that can detect radio transmissions across all frequencies? Would something like this be very complicated and expensive? If something like this is possible could someone please give me an idea as to where to look for information on how to complete this task?

Thanks in advance for any help.

Joey

I think what you may be asking, is, isn’t there a device that will detect radio transmissions across all frequencies - at the same time?

The key words here been “at the same time” versus having to start a scan at say, around 10Mhz and scan through the entire radio spectrum to, say 5Ghz, identifying all radio transmissions as it moves along from one frequency to the next. What you would like is a scanner/receiver that will look at the whole spectrum from 10Mhz - 5Ghz instantly?

Well, yes, there is hardware out there now that has the ability to look large chunks of the spectrum in one go (real time) – although not quite that big. Ghz sized snapshots can be taken, and there are pro grade scanners/receivers on the market that can scan 200Ghz – 300Ghz in less than a second. That s’ no problem – but been able to look at Ghz wide sections of the spectrum, real-time on an on-going basis, and process and extract orginal info – nope, we ain’t there yet (I exclude from my comments folks like the NSA, GCHQ and so on ....... I haven't got a clue what they are capable of).

The big boys (e.g. Agilent, Rohde & Schwarz … etc etc….) are producing receivers/scanners and analysers with digital sections quick enough now, that can “look at & listen to” chunks of radio spectrum around as large as 100Mhz - 150Mhz in real-time, and pass on the full content (whatever it may be) on a so-called on-going basis for long as may be required.

A chunk of rf spectrum like this, on an on-going-basis, requires HUGE HUGE amounts of computing resource to digitize & I/Q format (which is what has to be done), and then send on to HDD in real time, with sufficient resolution for analysts to be able to go into later, and extract whatever they may be looking for ……. whether it be analogue broadcast audio, digital satellite radio, TV broadcasting, Wireless internet, GSM phone calls...... etc etc. All these transmissions use different modulation techniques, different encoding, some are encrypted …… and so on and so on. There could be literally dozens of rf types of transmission that may be contained in any 100 - 150Mhz chunk of the spectrum.

Off the top of my head, such a recording would need to be around 10 – 12 bit at least in resolution to be sufficiently detailed for decent quality analogue as well as digital data to have retained its original content accurately. At that resolution, recording 100Mhz of spectrum over say 1hr, is going to chew up Terabytes of HDD !!!

One company that specializes in ultra-wide-bandwidth hardware is XcomSystems – take a look at http://www.xcomsystems.com/product/IQC-2110-RF-Capture-Storage - read the PDF notes attached to brochures in their “RF Capture & Playback” products section.

In short Joey - its one thing been able to look at and detect a chunk of the rf of whatever size - anywhere on/in the rf spectrum. It's a very different matter processing, to any meaningful or usable extent, the rf/radio activity that may be taking place across that section of the spectrum!
 
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