I downvoted this comment for the completely wrong analogy and misunderstanding of how radio works. So wrong, in fact, that it is hard to believe it was made in

I downvoted this comment for the completely wrong analogy and misunderstanding of how radio works. So wrong, in fact, that it is hard to believe it was made in good faith. Still, I am going to treat it as if it were. The problem is on the radar altimeter's Rx side, not on the Tx side. The radalt has Rx filters to reject noise on nearby frequencies. Cell towers have Tx filters to avoid broadcasting on nearby frequencies. But no real filter has 100% rejection outside the passband. That means that a 5G cell tower will broadcast some amount of energy within the spectrum defined for radalts. Also, radalts are not able to perfectly reject all energy that is outside, but arbitrarily close to their defined spectrum. A second factor is that power received by a radar falls as the fourth power of distance between a radar and the target (in this case, the ground). Tx power goes as 1/r^2. The target, having received that 1/r^2 power, then re-radiates it back to the radar, where it again falls as 1/r^2. That means radars have to be designed to detect very small amounts of power. Because physics. So the combination these factors leads to a situation where the high broadcast power of a cell tower inevitably leaks some energy into spectrum near that which radalts operate in, not all of which is effectively attenuated by the radalt's Rx filter. The small amount of energy that leaks past both filters can cause interference due to the sensitivity requirements of radalts. At a fundamental level, it was really stupid for the FCC to allocate high power transmitters in a band right next to radars. This is starting to be a pattern: See the attempted Light-Squared allocation next to GPS (for which the received signal strength on earth's surface is lower than the thermal noise floor). Based on the number of comments confidently proclaiming that radalts are somehow using spectrum they aren't supposed to, I'm starting to think that HN is being heavily astroturfed on this subject. > This is like your neighbor driving onto your lawn, and then demanding you move out of your house. They should drive right back onto their lawn. No, this is like your neighbor planting some very delicate flower near the property line and then asking you not to spray Roundup all over your property because some of it drifts onto his flowers.