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Long Range Laser Pointer Experiment

A laser pointer is mounted in a PVC "shotgun" and tested for DX.

The laser and its power supply.

The batteries were removed from an ordinary 3 mW red laser pointer and the laser connected to an external 5-volt DC power supply in series with a silicon diode. The voltage applied to the laser pointer was 4.3 volts DC. Current draw was 33 mA (140 mW). (This particular pointer is equiped with internal active current regulation.)

The shotgun under construction.

The material is 3/4" ID SCH 40 PVC water pipe, about 48" in length. (19mm x 1.2m)

The shotgun mounted on a tripod.

Not a very satisfactory mount.

The laser mount.

The left hand barrel is the sight. The laser mounting screws were adjusted to collimate the laser beam to the sight.

Aimed and ready to fire.

The target is about 60' (18m) away.

The laser operating.

The target.

The laser spot is 1" (25mm) to the right of the bull's-eye.

Positioned for long range tests.

Later in the day (after dark) we aimed the rig at a target in a tree about 300' (91m) away and, later yet, at a bicycle reflector nailed to a utility pole about 1200' (365m) away. The bicycle reflector shot was made difficult by the unsteady tripod mount. We then aimed the laser to a point on a golf course about a mile (1.6km) away and viewed the laser directly from that spot.

The target at 300'.

The laser spot now is about 8" (20cm) wide.
The effect out there was spooky. Batman arrived shortly after this photo was taken...

Direct view from 300'.

The white spot above and to the left of the laser is the moon.

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The view from the golf course (1 mile).

The laser appeared as a brilliant red searchlight. The digital camera imperfectly captures the effect.

This was not a very serious effort, but it does demonstrate the idea and was good for a few yucks. We speculate the laser, steadily mounted and properly pointed with a rifle scope or transit, would be seen (directly viewable with the naked eye) at a distance of at least 20 miles (32km).

[We have in fact now observed the laser at 22 miles (35km), see laser DX experiments.]

Laser Rifle

Gas pipe laser mount and Daisy 4x15 scope.


Outside, ready to fire

While the mount is still pretty wobbley, this rig is MUCH easier to aim.

The question has been asked: Why is the long barrel necessary? Why couldn't the bare laser pointer be used without the barrel?

There are four answers:

  1. The barrel provides a place to mount the scope semi-permanently,
  2. the barrel provides an easy way to collimate the laser and scope,
  3. the barrel provides side-lobe suppression for clandestine/secure operation, and
  4. it's cool..

The Future?

Related Links

Laser Beam Concentrator

Laser Pointer Audio Modulator

Laser DX experiments

Sewer-Pipe LED Projector

Laser Range Calculator/Estimator

Related External Link

Using Laser Pointers for Free-Space Optical Communications