The PA0KLT Low Noise VFO Synthesized Kit (Discontinued)

After 14 successful years the designer, PA0KLT, and SDR Kits have made the decision to discontinue this Kit.
A factor has also been the recent worldwide component shortage, which has seen the Si570 chips significantly rise in price and become difficult to source.
This page will remain to provide access to information and documentation for existing Kit owners.

Standalone VFO design
Built in LCD and Controller
No Computer required
Kits available with various frequency ranges
Optical Encoder available as optional extra

  • Output is a squarewave - minimum frequency is 3.450 MHz

  • Low noise Synthesizer chip controlled by an Atmel Mega 328 processor with PA0KLT Firmware

  • Controller with connections to an external 16 or 20 character x 2 lines LCD Display (16x2 LCD supplied in kit)

  • Firmware written in Assembler for optimum speed and control

  • Logical Outputs for selecting 1 of up to 16 external Filters for Amateur Radio Bands from 136 kHz - 440 MHz

  • A 96 step mechanical rotary encoder for tuning is supplied in the kit (Optional 128 or 256 step Optical Encoders supported)

    Optional Functions:

    Optional RIT (Receive Incremental Tuning)
    RIT is enabled by pressing the RIT, a second press on the RIT button disables the RIT offset. RIT is also disabled in TX/Lock Mode. A press on the 2nd button resets any RIT offset back to 0 kHz. The maximum RIT offset range is +/- 10 kHz/


Optional Fast Tuning

Fast Tune is enabled via a suitable Encoder fitted with switch or by a separate push button switch (Optional hardware required). When the switch is briefly pressed, this provides for a 25x Fast Tune rate, whilst a second press revert to the Normal Tuning as before. For example, with a 24 step encoder, enhanced by the firmware to 96 steps/turn and a 10 Hz tuning step selected this results in a resolution of 0.96 kHz per turn. When Fast Tune switch is enabled the resolution increased to 24 kHz per turn until Fast Tune is switched off again.

             PA0KLT V4.20 Connection Diagram for RIT & Fast Tune Options

             The PA0KLT Low noise VFO kit supplied with various Si570 Chips which set the maximum frequency range required up to 1417 MHz (1.417 GHz)

  • Kit A supplied with Si570CAC - covers 3.45 - 210 MHz - output is CMOS Square wave
  • Kit B supplied with Si570BBC - covers 3.45 - 280 MHz - output is LVDS Square wave
  • Kit C supplied with Si570DBC - covers 3.45 - 280 MHz - output is CML Square wave
  • Kit D supplied without chip
  • Kit E supplied with Si570DBA - covers 3.45 - 1417 MHz - output is CML Square wave
Please note that the PA0KLT kit is suitable for constructors with some previous kit assembly experience. Some components like capacitors (0805mm) & Si570 are Surface Mount Devices. Kits are complete and contain:


   A quality double-sided PCB
    Programmed Atmel ATMEGA 328
    6 pushbuttons
    Mechanical rotary encoder without switch
    All connectors
    LCD display with backlight
    Si570 chip supplied as ordered

PAOKLT Documentation

PAOKLT Applications

-Local Oscillator building block for home-brew receivers or tranceivers

-External local Oscillator for stand SDR hardware projects

-Wide range low noise test Oscillator output frequency programmable in steps from 1 Hz. upwards

-Multiband QRP CW tranceiver covering 3.5 MHz - 144 MHz with plug-in LPF

PAOKLT Kit Accessories

SMD Transformer WBC4-1WLB  (950 MHz)

SMD Transformer WBC4-1WLB (950 MHz)

£3.05 incl VAT: £3.66

Indicative prices in EURO €3,60

Indicative prices in USD $3.84