Frequency Counter

Features

• Original Design by DL4YHF
• Frequency range: 1 Hz-50 MHz
• Crystal Test Range: 4 MHz-48 MHz - Replaced with pre-amp circuit
• PCB size：8*5.3cm
• Sourced AliExpress Frequency Counter - Very inexpensive
• PIC-freq.counter-modification
• DL4YHF 50MHz counter on a Chinese TB-244746 PCB

Case

• P-Touch white on black labels

• Inexpensive plastic case
  • Plastic Waterproof Cover Electronic Project Instrument Enclosure DIY Box Case Junction Box Housing 100 x 60 x 25 mm Black
• BNC connector - female chassis mount
• 5.1mm Chassis mount power connector
  • 7-9V in

Rework - Add Pre-Amp

• Based on

• Uses extra transistor that would have been used by crystal tester oscillator
• Pre-Amp schematic

• When building kit, do not install

• Front side cuts - blue
• Jumpers Red

• Back side cuts

• Details of preamp input pin

• With parts

Testing

• 4.9152 MHz crystal
• Scope frequency counter shows 4.19520 MHz
• Freq Counter displays 4.9747 MHz
• Difference = 500 Hz or 0.1% accuracy
• Can only adjust the variable capacitor in narrow range