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I work at a local small airport (very small, if we get more than about 10 or 15 airplanes taking off/landing it's a "busy day") and I mow the runways (we have multiple grass ones).

Because of the visual obstructions of the tractor's cabin that I use I have to be even more careful than normal to check for in-coming planes and so I started looking into getting an air band radio for the tractor. However, they can be fairly expensive - not something I'd invest in unless I absolutely had to - and so I started looking into making my own.

I'd figured this was possible because I'd occasionally picked up communications on a cheap radio I had around my house (I live quite close to the airport, about a 5 minute bike ride). So, I went searching, and sure enough - this is a thing that is possible and has been done.

I found this post on Electrical Engineering.SE, Modify an AM/FM radio to an airband receiver, describing basically what could be done; and then this video done by MAKE, Weekend Project: Aircraft Band Receiver, showing it actually being done to cheap transistor radio.

Now, what I'm wondering is, is this a legal thing to do - or does the FAA have regulations on this sort of thing?

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    $\begingroup$ The relevant regulations would be FCC, not FAA, no? $\endgroup$
    – cpast
    Commented Dec 26, 2014 at 5:23
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    $\begingroup$ @NoviceInDisguise: I agree that it's not practically controllable, but in some countries listening to broadcast that is not intended for public (which includes aviation bands) is indeed formally illegal. $\endgroup$
    – Jan Hudec
    Commented Dec 26, 2014 at 11:04
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    $\begingroup$ It's surprising this isn't regulated. I'm not sure it's even wise. Consider if, at some point in the day, for some reason, your radio stops working. I don't want to cast doubt on your EE prowess, but your homemade radio would not be FAA certified, so this certainly seems like a plausible scenario. It's not clear that you would notice your radio had stopped working, and you might have a false sense of security and thus not be looking for incoming aircraft quite as diligently. This seems like a dangerous scenario, right? $\endgroup$
    – raptortech97
    Commented Dec 26, 2014 at 18:18
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    $\begingroup$ There is no restriction to monitoring airband frequencies in the U.S., so you shouldn't have to worry about FCC rules as long as you aren't transmitting. Where you could run into trouble, though, is with the FAA. I'm not sure about this particular use case, which is why I'm not posting an answer, but the FAA is generally pretty strict about using unapproved equipment for aviation operational safety purposes. Someone that knows the relevant FARs (if any) might be able to provide an answer here. $\endgroup$
    – reirab
    Commented Dec 27, 2014 at 8:47
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    $\begingroup$ Shouldn't your employer be providing you with appropriate safety equipment, rather than leaving you to jury-rig your own? $\endgroup$
    – David Richerby
    Commented Dec 27, 2014 at 13:59

2 Answers 2

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FYI, the runway is supposed to be closed XXX with NOTAM when it is mowed.

There is no FAA or FCC limit on constructing homemade airband receivers in the United States.

You can also construct transceivers. As long as you do not sell a transmitter you are allowed to make and operate up to 5 of them.

The exemptions covering low power transmitters are covered in Part 15 of Title 47 in FCC regulations.

The maximum unlicensed radiated output power for airband is 500 μV/m @ 3 m. Typical commercial airband handheld transmitters go up to about 1 Watt and base stations up to 50 Watts. For your purposes a 1 Watt transceiver would probably be reasonable.

Note that typical receiver/scanner designs have an oscillator in their mixer that can generate a small amount of RF noise. Normally the signal is so weak it is completely undetectable. Nevertheless, there are specialized receivers that have no oscillator that some people use to listen to airband with zero chance of interference.

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    $\begingroup$ That's transmitters; the question was about receivers. And Part 15 prohibits intentional radiation in much of the aviation frequency bands, and has 150 uV/m for much of the airband (88-216 MHz are 150 uV/m, per 47 CFR 15.209(a)). $\endgroup$
    – cpast
    Commented Dec 26, 2014 at 16:54
  • $\begingroup$ @cpast I updated the answer to cover receivers. The 150 limit is for constant transmission. Periodic transmissions (the normal case) have a limit of 500 as I wrote. $\endgroup$
    – Tyler Durden
    Commented Dec 26, 2014 at 16:59
  • $\begingroup$ @TylerDurden Thanks for the answer! $\endgroup$
    – RPiAwesomeness
    Commented Dec 26, 2014 at 21:18
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    $\begingroup$ While a receiver is good to keep you informed, if you ever need to warn away an aircraft, you'd need a transmitter, making the tractor a "ground station" requiring a license, and you personally would also need to be licensed to use it. As an employee of the airport, you might be covered by the airport's license to operate on its UNICOM frequency; I'd check with the airport's governing committee on this. In fact I'd question the airport manager's decision that it's not worth the expense; what's his liability for obstructing an active runway resulting in a collision? $\endgroup$
    – KeithS
    Commented Jul 20, 2015 at 21:53
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    $\begingroup$ Because those guys are operating aircraft; a radio mounted or carried in an aircraft is "licensed by rule" and doesn't require a special station or operator's license (which also technically means your use of the radio should only be in furtherance of your responsibilities as a pilot). Radios installed in anything that doesn't leave the ground are "ground stations" under FAA/FCC regs and require a license to operate in airband. However I think a HAM license is sufficient for this purpose so long as you're not endangering operations by being an asshat on a nearby tower frequency. $\endgroup$
    – KeithS
    Commented Jul 20, 2015 at 22:13
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If you want to listen only, you can airband scanners for ~$120USD. (wall-powered)

If you need to transmit or be portable, it's closer to $200.

https://www.sportys.com/pilotshop/avionics-and-radios/aviation-radios.html?dir=asc&order=position

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