No. Usually, all you need is to do is to send a signal - any signal - on a frequency you want to jam with enough power to overwhelm the target signal. A directional antenna won't get a milliwatt satellite signal if it starts picking up half a kilowatt of random noise, even if that noise is coming from the side. It's essentially a matter of how much power your jammer radiates and how high you can put it. Whether or not jamming interferes with other radio communication depends on how much of the spectrum your jamming signal covers.
There are plenty of other strategies, too (like not sticking to a single frequency, or picking frequencies that are likely to be too valuable to block with such a blunt-force method).
Depends on the wavelength and your surroundings. Imagine yourself wearing a cap that's little too small and half-transparent on the edges, walking on fresh snow, surrounded by snow mounds, trying to spot something on one of the hilltops nearby. So the cap mostly protects you from direct jamming signal, but reflections and bleed are still painful.
Now we're talking here about satellites, in particular LEO satellites, so you need a mass market (or at least commercial-grade) tracking antenna, which will have to look all across the sky and not just point straight up. In urban environments, there's a great chance there will be scores of decent reflectors (buildings) all around you for the jamming signal to bounce off, and as for bands, the ones used by Starlink are ones that are unlikely to be used much for anything else in places like Iraq - so they may as well just jam the whole band. And since Starlink is a commercial service, you won't be able to switch to something the government depends on (not to mention procure new antennas and adjust software on the transceivers).
The usual answer, then, would be a polarized filter and a more narrow aperture (e.g. goggles). The narrower the FOV, the less risk of glare.
That does mean an antenna will have to actively keep itself pointed at a moving point in the sky, but with GPS, a compass, a clock, and each satellite's orbital parameters, that should be a solvable problem.
The harder problem would be for the satellite to pick out the signal coming back from the ground without having to limit itself to a single ground station.
Huh?
Radios are Kilo/Mega/Gigahertz.
Light is Terahertz.
> The laser works by the same principle as the maser, but produces higher frequency coherent radiation at visible wavelengths.
There are plenty of lasers in the non-visible spectrum, I use IR lasers all the time.
Jammers (to my knowledge) operate by actively producing an inverted copy of the signals it actually sees. That is: it'd be reliant on non-directional signals. Any directionality / beam-forming would make jamming a lot harder, since it makes it a lot harder for the jammers to actually see the signal in the first place (let alone produce an inverted-waveform copy of it).
Jamming also tends to get in the way of other radio communications, so even if it was actually effective against satellite communications, it'd be a last resort and would likely cause all sorts of other issues.