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I am a hobbyist circuit designer. I recently moved to a home near an airport. I am directly under the flight path, and sometimes planes fly as low as 500-1,000 ft over my house. My circuits are moderate speed (few hundred megahertz up to maybe 1 GHz) digital logic at low power levels (<20 watts) and none are intentionally designed to be RF transmitters or receivers.

Are there any special safety considerations for designing and testing such circuits with aircraft taking off and landing so close by? My intuition is probably not, since there are many poorly designed and poorly shielded digital electronic devices in the world, including at and near airports, and I've never heard this cited as a safety concern for aviation. However, I don't even know what frequencies aircraft radar and communications operate on, so I'm kind of at a loss for how to reassure myself that I am not putting any aircraft in jeopardy if a circuit of mine starts malfunctioning in some unexpected way. For example, should I be using a spectrum analyzer to see what kind of RF my prototype boards are putting out? If so, how would I know what a safe level of RF power even is? Is there a good theoretical calculation I could do in advance to ensure that no significant RF energy is present 500-1,000 ft from the board I'm working on?

Conversely, is there a risk that nearby airport radar or radio-navigation equipment could induce unwanted currents in my boards that would lead to hard-to-debug logic errors? I have considered turning one of my closets into a copper-lined Faraday cage to test new PCBs in isolated conditions, but doing this would be rather costly. Are there better solutions?

jemalloc
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  • Are you making high power circuits with spark gaps, Tesla coils and that sort of thing? – Spehro Pefhany Dec 25 '22 at 21:12
  • No, nothing like that. Just ordinary digital logic at 100 MHz - 1 GHz, 3A max current draw. Am I safe not worrying about this in that case? – jemalloc Dec 26 '22 at 11:08
  • By the way, I do get your humor here. Of course a spark gap would cause wide band RF interference. So, I'm interpreting your comment as "don't be silly, no need to worry about this issue." Tell me if I'm misreading you... – jemalloc Dec 26 '22 at 11:21
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    Pretty much. AFAIUI aircraft comms and ELS are in the VHF band 100-300MHz roughly. So if your constructions are capable of interfering with terrestrial VHF TV from hundreds of feet then they could conceivably interfere with those. To get a large amount of power over a narrow band centered at certain specific important frequencies is not likely to happen inadvertently unless you're doing something odd compared to just making digital logic, and without an accidental effective antenna it won't get far. However, I've learned not to underestimate the ability of people to do bad things accidentally. – Spehro Pefhany Dec 26 '22 at 17:09

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Several ground control systems and radars at the airports use frequencies around 1000-1100 MHz for various needs (e.g. locating arriving aircrafts). However, the power of a signal as well as its polarisation is unlikely to be at the scale of what your electronics might produce as long as <20W is just an electrical power consumed by your circuit rather than a power emitted at a single frequency or broad band into the free space using some antenna.

Alex0xff
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    Thank you. I should have been clearer, but, yes, the figure "<20W" is referring to the maximum I*V that any of my circuits would ever draw. Obviously, most of that power is going to digital logic ICs and ultimately being dissipated as heat, not RF. – jemalloc Dec 27 '22 at 00:56