Grid dip oscillator:
Most amateurs know this device is, the Solid State Dip Meter, but how do you measure with such a device and how does it work?
Alan Wolke the W2AEW has an instructional video, in where he explains how the Dip Meter works and how to measure.
Below the text he wrote to accompany on this video:
De meeste amateurs kennen dit apparaat wel, de (Grid) Dipper, maar hoe moet je nu met zo’n apparaat meten en hoe werkt het?
Alan Wolke de W2AEW heeft een instructie video gemaakt waar in haarfijn wordt uitgelegd hoe dat nu werkt en hoe je meet.
Hieronder de tekst die hij (in het Engels maar dat zal voor de meeste amateurs niet zo’n probleem zijn) bij deze video schreef:
This video presents the basics of a Solid State Dip Meter, which is the more “modern” equivalent of the old classic Grid Dip Meter (GDO). The GDO was simply a vacuum tube based oscillator with a meter that read grid current as a measure of the oscillation strength/magnitude. The solid state dip meter uses a solid state RF oscillator and detector circuit to perform the same function.
The Dip Meter (or Dipper) I show in the video is a Heathkit HD-1250 that I built as a kid in 1976 or ’77.
The dipper is mainly used to determine or measure the resonant frequency of a circuit, antenna, 1/4 wave transmission line, crystal, filter, etc. You couple the dipper’s exposed coil to your “device” under test, and adjust the frequency of the dipper until a drop or dip in noticed in the meter. Once the dip is found, the frequency is read off of the dial.
The theory of operation is that the signal from the oscillator is injected into the circuit/device under test. Then the frequency produced by the dipper hits the resonant frequency of the DUT, the strength of the oscillation will decrease due to the resonant load.
There are a lot of applications for this: determining the resonant frequency of a circuit, or an antenna, of a crystal or filter, etc. Also, using known capacitors or inductors, you can use the dipper to help measure the values of unknown inductors or capacitors. You can determine 1/4-wavelength transmission lines and other resonant RF structures like traps. The meter can also be used as a RF signal source for testing receivers, etc.
By turning the oscillation level in the dipper to the point where is just goes away, the dipper can then be used as an absorptive wavemeter – or a frequency selective field strength meter.
The “Dipper” is a very flexible and versatile instrument, that has been around for decades, but isn’t seen that often anymore unfortunately.
Source: Alan Wolke de W2AEW YouTube channel with many more very interesting videos!