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VHF Dip Meter circuit

This is a simple VHF dip meter circuit.The DIP meter is the frequency meter by use the LC resonance circuit that adjustable until the frequency show peak amplitude. The circuit include variable frequency generator circuit, rectifier and a moving coil meter.

In the oscillator include two transistors T1 and T2. The tuning circuit include C1 and coil Lx this coil will is outside the metal box.

VHF Dip Meter circuit

When apply the power to circuit, the voltage from the oscillator will be rectifier by diodes D1 and capacitor C2. Then, send signal to P1 that use to adjust meter.


If bring the coil Lx near the others LC circuits, that resonance same the frequency is generated. This LC circuit will pull power from Lx, cause the lower voltage drop across the meter. The adjusting frequency by C1 if the frequency resonance can read frequency by the meter.

The coil made of copper wire No. 19 SWG or 1mm. Wrapped 2 times on the core diameter 15 mm. The frequency range 50-150 MHz.

This transistors No. BF494 can operate at frequencies up to 150MHz. If needed, use the higher frequencies to change the number BRF91. Which operate at frequencies up to 250 MHz. The capacitor C1 is 50 pF may be made of the mica capacitor value 100 pF 2 pcs in series.

This Post Has 9 Comments

  1. eine schöne schaltung,

    danke.

    73, walter

  2. Questions/comments:
    1. C1 (50pF) can NOT be two 100pF mica capacitors in series. The schematic shows this component to be a VARIABLE capacitor so the tank (oscillator Lx and C1) can be adjusted to the frequency of the nearby LC oscillator. When the needle on the meter drops, the Lx/C1 frequency is adjusted correctly. You then bring this oscillator circuit to a frequency counter to read the frequency. The meter dip only tells you when you are at the nearest proper frequency.
    2. Are the instructions for the “coil” for Lx? If so, what is the specifications for L1?

  3. Positive terminal of battery wrongly connected in your scematic

  4. The common type of “polyvaricon” variable capacitor with 210pF & 140pF sections wired in series would probably be OK for C1. This would give about 85pF maximum capacitance. 2N3904 npn transistors would be worth a try if you don’t have BF494s.

    1. Hi lan,
      Thank you very much for your good advice. You are very kind. Hope you come back to visit my site again.

  5. One of the readily available “Polyvaricon” variable capacitors would probably be suitable for the tuning capacitor C1. These often have two sections of 210pF and 140pF. By connecting the sections in series a 85pF maximum tuning capacitance results. If you haven’t any BF494s, it would be worth trying the common 2N3904 if you have some.

    1. Hi blacksmock,
      Thank you very much for your excellent advice. Your experience is very useful to us.

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