That's actually how spies send data back over the satellites:
>Unlike with SW signals, a radio signal to a satellite is very difficult to intercept and trace, as the waves are 'beamed' straight up rather than all around.
A helicopter with the right equipment flying over urban areas would have an easy job finding them and even pointing out the approximate location (eg. a building) where they're located. If the antenna was inside a huge apartment building, it would be hard to find the right apartment, if the transmitter was turned off, but with single family buildings, it would be easy.
Ham radio operators hide and then look for hidden transmitters for fun, so it's not that hard, especially with a budget that is given to the police.
You are very wrong sir. https://en.wikipedia.org/wiki/2-millimeter_band
>A helicopter with the right equipment flying over urban areas would have an easy job finding them.
That is not true. Helicopter would need to fly RIGHT into such directional and tiny beam. Which is nearly impossible to do in huge city. Even when flying 2m next to it, you would likely not detect it.
That is the reason why CIA had so much problem with pinpointing Iridium satellite phones back in Colombia in the 90's.
and yes, even with a laser (nanometer wavelengths) it's hard to produce a 2mm wide beam at a helicopter distance.