Finding the nodes[ edit ] Two methods are employed to find the nodes. 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. Lecher and early researchers used long thin Geissler tubes , laying the glass tube directly across the line. The high voltage of early transmitters excited a glow discharge in the gas. In modern times small neon bulbs are often used.
| Author: | Zolokora Yojinn |
| Country: | Maldives |
| Language: | English (Spanish) |
| Genre: | Literature |
| Published (Last): | 5 October 2005 |
| Pages: | 445 |
| PDF File Size: | 5.81 Mb |
| ePub File Size: | 12.5 Mb |
| ISBN: | 402-9-31620-839-4 |
| Downloads: | 48083 |
| Price: | Free* [*Free Regsitration Required] |
| Uploader: | Mazucage |
Finding the nodes[ edit ] Two methods are employed to find the nodes. 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. Lecher and early researchers used long thin Geissler tubes , laying the glass tube directly across the line. The high voltage of early transmitters excited a glow discharge in the gas. In modern times small neon bulbs are often used. One problem with using glow discharge bulbs is their high striking voltage makes it difficult to localize the exact voltage minimum.
In precision wavemeters an RF voltmeter is used. 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. 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 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. With care, Lecher lines can measure frequency to an accuracy of 0.
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. The frame must be made of a nonconductive material like wood, because any conducting objects near the line can disturb the standing wave pattern.
A simpler design is a "U"-shaped metal bar, marked with graduations, with a sliding shorting bar. Then the distance from the end of the link to the shorting bar is a half-wavelength. The shorting bar should always be slid out, away from the link end, not in, to avoid converging on a higher order node by mistake.
JURNAL ELEKTROKARDIOGRAFI PDF
LECHER WIRE EXPERIMENT PDF
Vujind How does it work — does anybody know? Thank you for this. Why does this so drastically differ from the values in the datasheet? A metal bar, or a screwdriver in my case, is put across the width of the two parallel wires, shorting them. In the photos you can see a measuring tape running the length of the wires for measuring the distance from the end esperiment the Lecher line to the nodes. Lecher line The next one further away is a full wavelength.
ELVOX 900 PDF
Lecher wires
.
ENGINEERING MATERIALS BY KENNETH G BUDINSKI PDF
My famous Lecher Wire demonstration
.