DIY guide for building and using the DFD4 programmable frequency counter with specifications and assembly instructions.
The DFD4 is a programmable frequency counter for HF and VHF/UHF bands, designed by Neil Heckt. It uses three ICs, a dot‑matrix LC display and can be powered from a 9 V battery for portable use or installed in a receiver.
The manual provides detailed specifications, component lists, step‑by‑step assembly procedures, testing methods, calibration instructions and optional features such as background‑lit display and offset adjustment. This manual is written in Dutch.
| Frequency range (HF) | 0 – 30 MHz |
|---|---|
| Frequency range (UHF) | 10 – 3000 MHz |
| Input impedance | 50 Ω |
| Maximum input voltage | 5 V |
| Power supply voltage | 8 – 20 V |
| Current consumption (HF mode) | 15‑20 mA |
| Current consumption (UHF mode) | 36‑45 mA |
The offset is set with three multi‑turn potentiometers (FINE, MEDIUM, COARSE) and the jumper J1 selects positive or negative offset.
A 9 V battery can power the DFD4 for at least eight hours without display back‑lighting.
The UHF prescaler uses the Fujitsu MB506 DIL‑8 IC.