At least in the US, there are already people doing it and anyone who gets caught is subject to massive fines, e.g.:
https://www.computerworld.com/article/2474412/data-privacy/g...
https://www.engadget.com/2016/05/25/florida-man-fined-48k-fc...
That said, anyone should indeed be filtering their output unless transmitting more than extremely low amounts of power (perhaps someone with radio experience could give a hand of thumb? Up to hundreds of microwatts sounds quite safe) as a matter of civility. Besides, you get to learn basic electronics by building a simple passive filter!
GPS is quite easy to jam with very low power. Something as low as 500mW could easily disrupt a fairly wide area. The reason being that GPS signals are generally already below background noise as measured from the ground.
Even with the first tests with 10mW in my room, iPhones at my house picked up GPS signal to know the time and timezone, which caused my flatmates to miss appointments and many websites stopped working due to certificates being expired by "2030".
Both numbers are correct, but 25W isn’t “insanely powerful”. The spec for GPS satellites lists the antenna gain at 13dBi. 25W fed through a 13 dBi antenna is just shy of 500W EIRP. Sitting near me is a 2W 2.4ghz amp and a 24 dBi parabolic antenna. That combo is just over 500W EIRP. The reason you stated (distance) is the big factor, over 12,500mi, the free space path loss is huge (182dB assuming flat gains). 500W is just shy of 27 dBW, so 27-182 is -155, which is a very very very weak signal.
Today, the Solt transmitter in Hungary operates at 2 megawatts.
https://en.wikipedia.org/wiki/Border_blaster
https://en.wikipedia.org/wiki/John_R._Brinkley#Brinkley_and_...
Low earth orbit satellites are much closer to the Earth, so transmitters need less power to cover the range with high quality signal. For example, NOAA satellites are able to send images of the earth at 5W that you can reliably receive with a dipole and a $5 amplifier.
Geostationary satellites are significantly higher, ~35000 Km, but stationary (duh), so they benefit from high gain, very directional antennas both on the satellite and the ground. They send high data and symbol rate signals for HD video of hundreds of channels, and each transponder sits at 15 to 150W (depending on many factors: band, area to cover, etc). They tend to have multiple transponders, though.
GPS satellites sit in the middle, pretty high up, so there's a ton of free space loss, in a non geostationary orbit, so high gain antennas are useless, plus receivers are supposed to be portable, hence there's no room for helix/axial antennas or arrays on the ground. So for this reason they have to ramp up the power to geostationary, TV broadcast levels, only to push a very, very slow data rate (50 bits/s).
A few milliwatts can easily block the sensitive input of a Police Repeater on the other side of town.
FWIW, your "Hundreds of Milliwatts" are routinely used by hams to communicate world wide.
And no, a simple bandpass filter WILL NOT clean up this rubbish. Its output spectrum is the base-band signal repeated over and over, all the way up to VHF. It would take a very capable filter to pick out the single product required. This is NOT the way to design a clean transmitter.
It will not only cause interference, but it will interfere with EVERYTHING within range.
Most output filtering is a simple Low-Pass Filter which is designed to remove harmonics. But by definition, harmonics are an octave removed from the fundamental. This horrid device puts out a closely packed comb of spurii from DC to daylight. A simple passive filter will not even come close to cleaning it up.
You first start with a sound design, then add filters to clean up the last of any unwanted emissions. Not the other way around.
And because these faults have been well documented, this equipment would most definitely be classed as an "intentional jamming device".
> FWIW, your "Hundreds of Milliwatts" are routinely used by hams to communicate world wide.
Read again, I've written "hundreds of microwatts" :)
And that's for a reasonably wideband signal! A narrowband signal with high power has a lot more potential to interfere with a specific application. I seriously doubt anything of that order specially with a rough bandpass (passive) filter around the frequency of interest can cause significant interference. Passive filters have <1 gain, so they shouldn't risk narrowband amplification of the weak signal. The background noise should be within this order of magnitude, no?
(I don't quite have the time to give numbers right now, but here's a source from quick googling: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7833115 -- the ambient noise should be on the other of .1 uW / GHz; at a few hundred meters away this competes with our wideband microwatt-scale transmitter?) I'll see if I can do some actual calculations later
> "The troublesome transformer was not replaced, but the building owner agreed to turn off the sign should problems arise"
This is a recent investigation that I found particularly intriguing. It involves a device used to monitor electric utilities that ended up interfering VZW's signal in Silicon Valley.