There's no amazing mystery behind how radar detectors work. In short, radar is a type of radio transmitter, and your radar detector is just a type radio antenna.
Your radar detector is simply picking up a radio signal, much like your car radio is getting a signal from your favourite radio station's transmitter.
With that in mind, your radar detector will work even if you can't (or don't want to) mount it at the popular spot at the top of the windscreen.
Just like a radio aerial, the higher up the better, but it still works low down too. In fact your radar detector will work on top of the dash with a bit of tape or velcro or Blu Tack if you find yourself missing the actually bracket mount.
It will also work mounted sidways, or upside down, sitting in the cupholder, on the passenger seat, or even on the floor. Higher is better, but it's just a radio signal.
If you have something with those directional arrows like the Uniden R8nz or Escort Redline 360c, it will need to be mounted somewhere that makes allows the front/rear antennas to make sense of direction. Even those WILL still work just flopping about on your seat but the information will be confused, front vs rear alerts will be screwed up.
Also, if you are relying on the GPS database for camera alerts, the detector needs some sort of “line of sight” with space.
Armed with this not-so-technical information, it makes mounting a radar detector without an official mount much easier, especially if it's just short term. Similarly when it comes to fitting a radar on a motorbike, the fact it can be installed anywhere, even in your pocket, makes using one a little less challenging as well.
Again, higher up and clear of obstruction is best, but not always possible.
As long as the radar detector isn't behind metal/steel, it will work.
Aftermarket metallic-based tint strips at the top of your windscreen will restrict your detector's performance.
On that point, a LOT of modern vehicles have very fancy windscreens.
Heated windscreens, electromagnetically sheilded windscreens and even some newer "acoustic glass" will affect your radar detector.
The last point worth mentioning is the effectiveness of laser alerts. We often hear drivers telling us they have their radar detector high up on the window so it can pick up laser. The thing is, police usually aim at a much lower point on your car, like the license plate. Not only that, it takes less than three tenths (3/10s) of a second for them to actually lock your speed. The common myth is that maybe your laser will pick up stray or "wash" laser signal from one being aimed at another car. Chances of this actually happening though are very slim, the laser is just a couple of millimetres and not a big wide beam of light, and nothing like radar technology.
If your detector says "laser":
- It's probably a false alert
- It takes longer to say "laser" than it takes for them to record your speed
- You're not going to slow down in time
With this in mind, it helps you find the practical and convenient mounting location for your radar detector - laser is not a factor.
We actually recommend disabling laser alerts on portable radar detectors.
TIP: If you're using a Uniden R7, R8, or even an old Valentine 1 in a right hand drive car, consider mounting your detector above the air vent between the instrument cluster and driver door. Makes it easier to see, if you think you need to see the display.