Lichtsprechgerät 80/80

Li Spr 80

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This is a 2-way audio communication equipment.
The signal is transferred on a light beam from a 5-watt bulb.

The light beam is modulated with a light phase modulator.
The light beam is AM-modulated with a moving prism.
The position of this prism is manipulated of the transmitter audio amplifier.

Red or IR filter can be inserted in the beam.
Receiver and transmitter have one lens each.
Light detector is placed 250 mm behind the receiver lens.
Diameter on the light detector is less than 1 mm,
so the direction of the unit is very important.
Diameter of the light beam is only 1.4 meter at 250 meter from the transmitter lens.
This will give a diameter of 7 meter 1 km away.
An RV2P800 tube is connected directly to the light detector as a preamplifier.
Diameter on the receiver and transmitter lens is 80 mm.
Manufactured by Carl Zeis Jena.

Technical data from the handbook:

Here are pictures from the second 2-way test of my LiSpr-80’s.
The distance between station A and B was 2000 meters.
The test was done on the island Fur in Denmark 12. jun. 2004.



Egil adjust the direction of the optic at position A.




Station A is located on an old barrow.







Here is the direction finder of LiSpr.80.
The red area in the picture is the actual light beam transmitted from LiSpr-80.
This is the size of the beam at a distance of 2km.
The black rectangle at bottom of the photo is the transmitter modulation monitor.




This is the actual distance from position B to position A.
The light beam from station A can not been seen on the photo, but it can bee seen with the eyes.




Marie at position B.




The communication is very good.




We also tested communication with red filters
with good results. The light beam was invisible with red filters at 2km.

Here are pictures from the first 2-way test of my LiSpr-80’s.

I have worked on the equipment in one year before this test.
Both the optics and electronics are restored. A new power supply is also designed.
The power supply deliver all the voltages needed for operation of the LiSpr-80.
The distance between the two LiSpr-80 were 300 meters.



Egil at position A. The first signal received.




Marie at position B.




Egil have here switched on the reed filter.




Marie has fine-tuned the direction with the direction-finder optic.




Here is the light from position A. Here with white light.

These are pictures from the first test of communication to and from a reflex.

Lichtsprechgerät 80 in use.

Lichtsprechgerat 80 in use. Adjustment of the optic unit.
It is important to adjust direction of the optic unit within 0.2 degree.

Lichtsprechgerat 80 in use. Communication via light.

Pictures are owned by LA6NCA.

Li Spr 80, part two

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