[pdabbadabba]

Previous discussion of a similar project, by [evidently] the same person: http://hforsten.com/6-ghz-frequency-modulated-radar.html

As before, this is totally awesome---until the FCC (or other national spectrum regulator) shows up at your door...

Here is an assortment of things that the author might be interfering with in the neighborhood of his 5.5 GHz carrier frequency: https://wirednot.wordpress.com/2014/01/07/what-else-is-in-th...

Some of this is the sort of stuff you really don't want to interfere with--both for safety reasons, and because of the likelihood of enforcement.

Next time I suggest that the author look into whether his jurisdiction will grant him an experimental license so he can do this legally. In many jurisdictions that is cheap and easy (unless, of course, you want to operate in a band where the interference risk is just too high).

Edit: I see the author is in Finland. Unfortunately for the author, I'm guessing this changes nothing since these frequencies are regulated both nationally and internationally. But it does mean that there is probably some local variation in the exact services that might be subject to interference. And who knows: maybe in Finland the 5.5 GHz band is a "do whatever you want at any power level you want" band. But I doubt it...

[falcolas]

Or he has his amateur radio license and is licensed to operate at higher power levels.

Even unlicensed, he has up to 25mw of power and 8.5db antennas (which with 25mw or less can give you upwards of a mile of clean signal), which may be sufficient. Hard to say.

[pdabbadabba]

Does an amateur license allow you to operate a RADAR system? I doubt it. I had thought that amateur operators were somewhat limited in the sorts of hardware and operations they are permitted. (E.g., type acceptance of equipment when operating outside designated amateur bands.)

And in the U.S. at least the bands around 5.5 GHz (the so-called U-NII-2 and U-NII-2 extended bands) are subject to lots of interesting rules for unlicensed operation, including the ability to detect and avoid incumbent RADAR signals. https://transition.fcc.gov/bureaus/oet/ea/presentations/file...

Of course, I know literally nothing about the Finnish rules that actually apply here...except that, thanks to the ITU, they probably bear some resemblance to the U.S. rules.

[semi-extrinsic]

Radar systems are fairly common on boats larger than ~30 ft, and you can operate those without any license at all. The latest generation devices are all broadband, working on the principle that if you spread your broadcast over a wide enough range, the power you're broadcasting on any given band is very low, i.e. legal and not causing interference for others. Maybe this guy is working off the same principle?

[pdabbadabba]

You don't always need an operator license but, when you don't, you typically do need properly certified equipment. (This is also why you don't need a license to use Wi-Fi.) The rules vary by service and by frequency band.

I'm no expert on boat RADARs, but I'd bet that, 1) they operate in bands allocated for that sort of use and 2) that they have been either type accepted or certified by the FCC to comply with whatever rules govern their band of operation.

[falcolas]

> Does an amateur license allow you to operate a RADAR system?

Yes, conditionally. RADAR does not fall under the "specifically prohibited" rule for communications, but it's also not explicitly listed as "specifically authorized" either. Likely up to the discretion of whatever FCC official you asked.

http://wireless.fcc.gov/services/index.htm?job=about_1&id=am...

> the ability to detect and avoid [interference with other] signals.

This is a requirement for all amateur radio transmissions. However, so long as you take reasonable precautions (and react to any reports of issues), you can do it.

In my (unprofessional) reading of the phrase "You determine for yourself whether your communications should be transmitted on amateur service frequencies", a reasonably powered experimental radar system which doesn't interfere with other services would be OK.

[Animats]

I wondered about that, too. There's a worldwide ISM band at 5.725 to 5.875 GHz in which you can run radars. But he says he's sweeping from 5.2GHz to 6 GHz. That's a lot of spectrum to be using. There's lots of stuff in there, including satellite links and aeronautical radionavigation.

Here's a similar project which is in the 5.8 to 6 GHz range. With a little work, they could probably make it stay in the ISM band there. One big frustration of gigahertz RF work is that the test gear you need to see what's happening costs far more than the project. I tried to build a frequency-modulated LIDAR once, and ran into that.

[1] https://hackaday.io/project/1682-simple-low-cost-fmcw-radar

[CamperBob2]

He's putting out a signal on the order of 1 milliwatt. Interference is a nonissue.