TR1 & TR2 are the standard 10mm IFT type tuning coils. TR1 comprises of 20turns of 36SWG enameled copper wire, while TR2 comprises of 35 turns of 36SWG enameled copper wire. These, along with the 10pF capacitor in parallel make the basic tuned coils for generating 2.9 to 3.0 MHz and 4.0 to 4.35 MHz Local Oscillator frequencies. An air variable capacitor like the 2X gang from Philips (220pF or 330pF range) will be sufficient to vary the Local Oscillator frequencies up to about 350kHz bandwidth.

Transistors Q1, Q2 & Q3 (all BC547s) act as oscillator & buffer amplifier stages. The generated signal after this amplification is passed through Band Pass Filters TR3 & TR4 to filter out any harmonics that may be present. TR3 has 45 turns in the primary and 6 turns in the secondary, while TR4 has 65 turns in the primary and 6 turns in the secondary winding. Both IFTs use 36SWG enameled copper wire. This filtering gives a clean required signal from the VFO. TR1, TR2 and TR3, TR4 are switched from the front panel for 7 / 14MHz operation as required. OMRON make DPDT relays are used for this purpose.

VFO output signal from the Band Pass Filters is sampled and analyzed by the PIC 16F84 Microprocessor program and the frequency is displayed on the LCD which is mounted on the back-side of the VFO PCB. The IF shift, i.e., 10MHz in our case, is added or subtracted, as per the band selection, by the Microprocessor program and accordingly the actual frequency in use is displayed. This makes it convenient for the operator to know where exactly he is parked. While the VFO uses +12V for its operation, the PIC uses +5V. Check these voltages before powering the VFO board. Back lit LCD normally draws around 250mA.