I debated putting this question on the electrical engineering forum vs. here. I settled on here since I figured many of you amateur radio experts have probably wondered about this too.

I am interested in seeing a graphical output of all of the various frequencies that are around me. Think of this as a broad spectrum analyzer that works across as much bandwidth as I am able to access. I am not interested in the content, just what frequencies are being utilized.

For example, I would love to see how the RF environment changes as I drive my car to work every day. Are there hotspots? What is the strength? Does it vary over time? A graphic interface that shows signal strength and the frequency would be interesting as well.

I have done several Google searches on this, and also searched on these forums. I don't have the right lingo as I can't seem to come up with anything worthwhile.

Appreciate your help / advice on this. Thanks.

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    $\begingroup$ well, define what you mean with "RF environment", and what you mean with "changes". RF is every electromagnetic wave between 3 kHz and 300 GHz, and there is, due to physics, not a single device in this world that covers all of that. So, you'll need to restrict yourself to a piece of that. You mention "hotspots" <- could you define that? $\endgroup$ – Marcus Müller Jan 19 '17 at 9:57
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    $\begingroup$ What's the difference between the thing you describe that's like a spectrum analyzer, and an actual spectrum analyzer? $\endgroup$ – Phil Frost - W8II Jan 19 '17 at 19:01
  • $\begingroup$ Thanks for all of the attention to this question. My interest in this area basically started when I bought a radar detector for my car. I know that many of the false positives I get on the K band may be the automatic doors near shopping malls, but it still got me thinking about this. As for the spectrum I am interested in, it is predominantly radio waves - UHF to VLF in the link that Phil included below? $\endgroup$ – user9062 Jan 20 '17 at 3:44
  • $\begingroup$ Your false positives from automatic door openers are predominantly on the on the X-band but technology evolves so they may well be moving to other bands. $\endgroup$ – SDsolar Jan 23 '17 at 4:04

You want all the frequencies?

Let's take it from the top down. You probably want to start with a Geiger counter for the highest frequencies. Hopefully you don't detect much with this.

Below that are frequencies usually called "light". Your eyes have some of that covered. The infrared and ultraviolet bits will need specialized cameras.

Around 300 GHz electromagnetic radiation tends to stop being called light and start being called "radio waves". What you are describing sounds exactly like a spectrum analyzer, and specifically one with a very wide bandwidth. Expect to pay a lot of money. I don't know if anyone makes a spectrum analyzer that covers the entire RF spectrum, so expect to buy several.

You can expect (among other things) that your spectrum analyzer will have a waterfall display so you can visualize RF radiation in time and frequency.

You can go a little cheaper with an SDR, which can also have a waterfall display if you don't need the precise calibration and whatnot that comes with a spectrum analyzer. Getting one that goes from 0 Hz to 300 GHz is still going to be expensive. For example the USRP costs approximately $1000 and goes up to 6 GHz. You'll need a variety of antennas and daughterboards to make it all work. That leaves just 6 to 300 GHz for which you'll need to purchase additional radios.

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    $\begingroup$ Ha! Geiger counter. Love it. ;-) Upvote. And yes, I agree that SDR is the way to go. I use a Ham-it-up for MF and HF, and an old DBS downconverter to bring 2.4 GHz down to 400 MHz. Of course, I have to flip switches (using relays) to go outside of the normal SDR ranges with the converters. I'd also mention that I can switch in preamps for the higher frequencies; they amplify the noise produced by the converters along with the signals, so I only use them (rarely) in native mode. The price is right for the RTL-SDR units on the market so that's a great place to start, with SDR# software. $\endgroup$ – SDsolar Jan 20 '17 at 19:09
  • $\begingroup$ This has been really helpful. The key words you guys have helped define have helped me hone my education via Google. Am I correct that a setup similar to this (plus a PC) puts me on the right track: wacug.org/otherether.html? Thanks - $\endgroup$ – user9062 Jan 21 '17 at 5:34
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    $\begingroup$ @OverlordvI That's one way you can go, though you may be reluctant to open your nice radio and hack into it. You might also look at the Softrock kits. They are very cheap ($20 or so) and work through your computer sound card. $\endgroup$ – Phil Frost - W8II Jan 21 '17 at 13:26
  • $\begingroup$ Definitely pick up a RTL-SDR unit at the usual online sources, (Amazon and eBay), then download SDR# (SDR Sharp) software for free. Plug it into a Win8.1 laptop USB and give it a try. Total cost is under $50, including antennas . The whole thing is portable if you want. At home I use a discone for 27-1200 MHz, and dipoles (on one feedline with a balun) for lower bands. Keep using Google - there is a lot of collective knowledge out there, including software add-ons for decoding signals. With an AK Arrow antenna you can hear the Space Station on 145.8 MHz and see their SSTV at 145.850 MHz. $\endgroup$ – SDsolar Jan 23 '17 at 4:53
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    $\begingroup$ A geiger counter works by detecting the ionization resulting from high-energy EM "particles" striking other particles. I use the term particle purposely because the dynamics of EM waves no longer works at those energies (gamma rays and above). Adding up-end completeness to @PhilFrost-W8II answer, I suggest something like LHC (Large Hadron Collider) or maybe SLAC or Fermilab as well. $\endgroup$ – K7PEH Jan 23 '17 at 19:09

You probably want something like a 'waterfall' display that many Software Defined Radios (SDR) give. Search for SDR and waterfall display! You can get set up fairly easy with a computer and dongle.

  • $\begingroup$ Welcome to ham.stackexchange.com! Our site is different from typical forum-style sites; our goal is to compile a high-quality database of questions and answers. Have a look at the tour. Sorry to be critical, but your post isn't much of an answer. We're glad you're here, and we'll look forward to more from you, but please be more complete next time. 73! $\endgroup$ – rclocher3 Jan 20 '17 at 20:06
  • $\begingroup$ Yes indeed. I see you are new here so please allow me to mention that for an answer it is best to flesh it out with specifics and examples. Upvote anyway, because you just described SDR#'s display running with a RTL-SDR dongle. Total investment is under #50 for the RTL-SDR radio (that comes with rudimentary antennas) and the free SDR# software. Feel free to edit your answer with details to attract more upvotes. $\endgroup$ – SDsolar Jan 23 '17 at 5:04
  • $\begingroup$ An RTL-SDR with a waterfall app would run just fine on a Raspberry Pi. So an Pi with a small display, RTL-SDR dongle, antenna and USB power would be well under $100 (USD), and work just fine in a car. $\endgroup$ – hotpaw2 Feb 4 '17 at 19:52

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