A. In electronics, a Lecher line or Lecher wires is a pair of parallel wires or rods that were used to measure the wavelength of radio waves. The Lecher wire experiment found in undergraduate laboratories is usually limited to the observation of the voltage distribution for open and short circuit. An improved Lecher wire experiment. To cite this article: M B Allenson et al Phys. Educ. 8 View the article online for updates and enhancements.

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For two parallel cylindrical conductors of diameter d and spacing D. Another angle showing the diode. Why does this so wirs differ from the values in the datasheet?

Email required Address never made public. A metal bar, or a screwdriver in my case, is put across the width of the two parallel wires, shorting them.

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Using a Lecher Line To Measure High Frequency

The next one further away is a full wavelength. They were also used as lechroften called ” resonant stubs “, in UHF and microwave radio equipment such as transmittersradar sets, and television setsserving as tank circuitsfiltersand impedance-matching devices.

Therefore the magazine’s copyright was not renewed and it is in the public domain. Less than half baked idea, but could a similar setup be used to leched the swinging length of a guitar string?

One problem with using glow discharge bulbs is their high striking voltage makes it difficult to localize the exact voltage minimum. The shorting bar is slid down the line and the position of two successive current minima is noted, the distance between them is half a wavelength. In modern times small neon bulbs are often used. Or if you rather use technology from 2 centuries ago, use that I suppose.


The other method used to find the nodes is to slide the terminating shorting bar up and down the line, and measure the current flowing into the line with an RF ammeter in the feeder line.

Lecher line wavemeters are usually built on a frame which holds the conductors rigid and horizontal, with a track that the shorting bar or indicator rides on, and a built-in measuring scale so the distance between nodes can be read out.

So the distance my screwdriver was off by was 0. You are commenting using your Facebook account. If the file has been modified from its original state, some details such as the timestamp may not fully reflect those of the original file. Wure would be great to see a visual explanation showing using a light particle model- showing how the light particles are absorbed and create the electric potential between both sides of the diode when the screwdriver is at a node.

By using this site, you agree to the Terms of Use and Privacy Policy. Lecher wire demonstration apparatus with lamp for indicating the point of resonance. One of those ways is to have the bar be two terminals of a neon bulb. Newnes Guide to Television and Video Technology. A Lecher line is a pair of parallel uninsulated wires or rods held a precise distance apart. In other projects Wikimedia Commons.

The frequency f of the waves can be calculated from the wavelength and lecyer speed of the waves, which is the speed of light c:. So the line presents an impedance to the applied power which varies with its length; when a current node is located at the entrance to the line, the current drawn from the source, measured by the ammeter, will be minimum.


The bulb goes out at the nodes, where the voltage is zero.

R Jessop [15] uses a Lecher line anode tank. If the indicator has too low an impedance it will disturb the standing wave on the line, so a high impedance indicator must be used; a regular incandescent bulb has too low a resistance.

File:Lecher wires and oscillator 1932.png

Public domain Public domain false false. Modern Dictionary of Electronics. In precision wavemeters an RF voltmeter is used. Permission Reusing this file. Lecher line, oscillator and other equipment. This site uses Akismet to reduce spam.

Does that make sense? To really make this article shine, it would have been nice to go back and verify the measurements wide some known standard.

5N – Standing Electromagentic Waves in a Wire (Lecher line)

There seems to be something to that. As a typical example, something like a Colpitts oscillator may be used, tuned with a varicap diode that changes its depletion capacitance strongly as the bias voltage across the diode changes — which is what allows control of the oscillator frequency from an applied bias voltage.

This work is in the public domain because it was published in the United States between and and although there may or may not have been a copyright notice, the copyright was not renewed.