> the new capacity had caused all of the servers in the fleet to exceed the maximum number of threads allowed by an operating system configuration. [...] We didn’t want to increase the operating system limit without further testing
Is it because operating system configuration is managed by a different team within the organization?
No capital letters, though. It is important to follow all security rules. Weakest link and such. If only his password was Maga2020!, it would be impossible to hack.
> if you know the modulation and the frequency the receiver uses
Number stations on short waves all use AM, so you know the modulation. But you don't need to know it, superhet works the same way with any modulation. You need to know the number station frequency, receiver's intermediate frequency, and guess whether its above or below.
> in such a way that there is absolutely no power radiated out of the reception antenna.
I'm not saying there is absolutely no power radiated out of the reception antenna, only that there is not enough power to reliably detect and localize, given the noise and interference from other sources.
If you want absolutely no power radiated out of the reception antenna, you can still do it. Feed some local oscillator frequency, inverted, into the antenna to cancel the remaining leak. But as far as I know, nobody bothers since some leakage is not a problem.
> Any kind of magnetic or capacitive coupler is bi-directional.
True, but in many designs there's also at least one transistor stage in the preamp, and that is not bi-di. There is some stray capacitance between collector and base, but not much.
> Maybe with today's hardware capabilities it would be possible to pull the whole thing into the digital domain at a very early stage
It is possible, but unnecessary. The last radio I built has quadrature sampling detector with FST3253 and handful of op-amps. Most SDRs also do I/Q sampling with two slow ADCs, much simpler than a single high-speed ADC.
You can make a small (relative to wavelength) loop antenna that has a sharp minimum, but it will be very inefficient. You want your directional antenna to have a sharp maximum (high gain) so that it can increase signal to noise ratio.
There is a big difference between spectrum analyzer hooked up directly to the input of the radio and an antenna in a van several blocks away, with reflections and noise thrown in.
A directional antenna has to be much larger than wavelength. Won't fit in a van if we're talking about HF (with wavelengths measured in tens of meters).
Only if it's poorly designed (leaks local oscillator frequency back into antenna) and not shielded.
Modern receivers use quadrature sampling detectors rather than traditional superheterodyne. In that setup any leakage would be on the same frequency and harder to detect.
I expected to see something along the lines of vans with directional antennas driving around Moscow listening for spurious emissions from local oscillators of superheterodyne receivers 465 kHz away from the number station frequency, as in Operation RAFTER.
There's a good reason why many laws in math and physics have two or three names. They are oftentimes discovered simultaneously by several people and it's not always possible to tell who was first.
The underlying assumption behind false positive rate is that tests are independent and identically distributed. If in practice this is not the case, then false positive rate becomes misleading.