In electronics, a Lecher line or Lecher wires is a pair of parallel wires or rods that . Kundt’s tube experiment which is used to measure the wavelength of sound. The Lecher wire experiment found in undergraduate laboratories is usually limited to the observation of the voltage distribution for open and. I had this experiment in my Physics Waves and Optics lab, so I of the frequently asked questions for the experiment: Lecher Line(Wire).

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Also in my setup the other end of the line is open, the wires are not wirr together there. Detecting really tiny current with a long filament, huge magnets, and some optics. New Jersey Society for Amateur Scientists.

They were also used as componentsoften called ” resonant stubs “, in UHF and microwave radio equipment such as transmittersradar sets, and television setsserving as tank circuitsfiltersand impedance-matching devices.

That setup really helps de-mystify its mechanical equivalent at sonic frequencies, the transmission line speaker, and the currently popular mathematical model for it as described by Martin J. Commercially available and ohm twin lead balanced ribbon feeder can be used as a fixed length Lecher line wwire stub.

The next one further away is a full wavelength.

One answer is to put away the oscilloscope and use the rest along with a length of wire instead. The bulb goes out at the nodes, where the voltage is zero.

An improved Lecher wire experiment – IOPscience

When the screwdriver is between nodes, the voltage is less than 0. Apparently the screwdriver causes a reflection creating a standing wave of voltage and current on the line.


The Speed of Light. Lecher line circuits can be used for the tank circuits of UHF power amplifiers.

Using a Lecher Line To Measure High Frequency

There seems to be something to that. The frequency f of the waves can be calculated from the wavelength and the speed of the waves, which is the speed of light c:. In the photos you can see a measuring tape running the length of the wires for measuring the distance from the end of the Lecher line to the nodes. Form the wire into a Lcher line.

Lecher line

The waves reflected from the short-circuited end interfere with the outgoing waves, creating a sinusoidal standing wave of voltage and current on the line. So the distance my screwdriver was off by was 0. One of those ways is to have the bar be two terminals of a neon bulb. It would be great to see a visual explanation showing using a light particle model- showing how the light particles experimet absorbed and create the electric potential between both sides of the diode when the screwdriver is at a node.

Another angle showing the diode. Quarter-wave Lecher lines are used for the tuned circuits in the RF amplifier and local oscillator portions of modern television sets.

The shorting bar should always be slid outaway from the link end, not into avoid converging on a higher order node by mistake. This short circuiting termination reflects the waves. R Jessop [15] uses a Lecher line anode tank.

Why does this so drastically differ from the values in the datasheet? The nodes are much sharper than the antinodes, because the change of voltage with distance along the line is maximum at the nodes, so they are used. One end of the rods is connected to the source of RF power, such as the output of a radio transmitter. As shown in the above photos, I added the diode loop to the collection of loops at the end of the Lecher line. In other projects Wikimedia Commons. Enhanced version and more background: Fill in your details below or click an icon to log in: So that is what a Lecher Line is!


As I slide the bar along the wires, it influences the waves. A metal bar, or a screwdriver in my case, is put across the width of the two parallel wires, shorting them.

Using a Lecher Line To Measure High Frequency | Hackaday

Propagation velocity depends on the dielectric. In many ways Lecher lines are an electrical version of the Kundt’s tube experiment which is used to measure the wavelength of sound waves.

You guys should do a retrotachular on ECGs. This reminds me of the fun part of physics classes. Two methods are employed to find the nodes. In the first photo above, the oscillator is pulled back a bit to make things clearer.

You are commenting using your WordPress. But if I HAD to…. Or if you rather use technology from 2 centuries ago, use that I suppose. Retrieved March 23, What follows is a bit about Lecher lines, how I did it, and the results. By using our website and services, you expressly agree to the placement of our performance, functionality and advertising cookies. How does it differ from the POS?