Frequency Synthesizers and Sources

AD9852 DDS Source  Click to enlarge AD9852 DDS Module
A single PCB module for an RF source for up to around 100MHz with control of frequency, amplitude, phase and other parameters over a serial / RS232 interface with simple text-based commands. The on-board PIC controller can be reprogrammed for a multitude of frequency generation and modulation tasks. -- The updated Mark 2 version -- PCB Layout - if you want to roll your own
See the Software page for driving this module


AD9850 DDS Board PCB layout for the old design, originally published in Radcom November 2000

AD9850-Controller using Rotary encoder, LCD and pushbuttons to set the frequency. Includes 16 memories. AD9850-Controller.zip Full Archive with PIC code and PCB Layout

AD9850 Serial Control Controls the DDS using ASCII commands on RS232 interface. AD9850_Serial.zip Full Archive including PIC code


PIC_DDS.pdf A low frequency DDS using just a PIC and R-2R ladder. Generates frequencies up to about 40kHz with two tone FSK. Frequencies can be user set via ASCII / RS232 interface with auto baud determination. Two FSK options; one allows standard continuous phase FSK, the other uses frequency exchange keying keeping each of the two tones coherent and is more suited to weak signalling. See a comparison of the two FSK_Types.pdf
The .zip archive as above, and includes all PIC source and .HEX files for both FSK versions and a simple single tone demonstrator. PCB layout in various .PDF formats for home constructors.
- Now includes a dual channel version with 90 degree phase shifted I/Q outputs for direct image cancelling RF upconversion. Uses the 28 pin 16F870 PIC


VHF Synthesizer Module - VHF Synthesizer Module -
Small standalone module for up to 170MHz. Controlled via RS232 serial interface with ASCII commands
VHFSynthModule.zip Hi-res diagrams, design utilities, PCB, PIC Code Bugs, modifications, corrections
SOLD OUT No more mini kits available - sri folks !
LTC6946 Synthesizer Module  Click to enlarge LTC6946 Integrated Synthesizer -
A PCB and design for using the LTC6946 up to 6GHz Integer-N synthesizer. An integral output divider allows output frequencies down to 370MHz to be generated.
This chip has an integral VCO and needs only a reference frequency input. An on-board PIC controller allows the chip's registers to be set by sending the register contents as ASCII text on a serial RS232 interface.
NEW - Alternative PIC software allows one of four pre-stored frequencies to be selected with switches or links. Each frequency can be set up using a serial interface
Typical Spectrum at 3.4GHz,  Click enlarge

Download complete archive

PCBs available here


LMX2541 Fractional_N Module  Click to enlarge LMX2541 Fractional-N Synthesizer -
A PCB and design for using the LMX2541 up to 4GHz Fractional-N synthesizer. This chip has an integral VCO and needs only a reference frequency input and a controller to allow the chip's registers to be set via the SPI interface. An integral output divider allows output frequencies down to 32MHz to be generated. Download complete archive

A design for a separate PIC controller using ASCII text commands on a serial interface is included.
Typical Spectrum at 432MHz,  Click enlarge Alternative PIC software for generating WSJT modes and for use with a rotary encoder / LCD will be available in due course.

Programming and using Fractional-N Synthesizers with MFSK / WSJT Modes

JTxx on the LMX2541 PIC Assembly Code and symbol generators for generating JT4 and JT65 with the LMX2541 Fractional-N Synthesizer

PCBs Available, see The JNT Shop for details.


LMX2470 Fractional_N Module  Click to enlarge LMX2470 Fractional-N Synthesizer -
A PCB and design for using the LMX2470 2.6GHz Fractional-N synthesizer. With a separate VCO and reference frequency input, the PCB provides a convenient way to install the chip, a high speed op-amp active filter, power supply regulator and a PIC based controller allowing the chips registers to be set using ASCII text commands on a serial interface.
Commands have been included to allow real time programming for narrow band data modes such as JTxx.
Download complete archive
PCBs NOW SOLD OUT (LMX2470 Chips and the LM6211 OPAmp are available from RS Components, Stock Nos 534-4894 4.28 and 651-1382 respectively)


Serial SPI Interface PIC RS232 to SPI Interface Small postage stamp sized module to interface a COM port to a synthesizer or DDS device. A 12F629 PIC is programmed with the appropriate firmware for the chip in use. A common four or five pin header connection is used for all target devices
Complete archive including serial driver code for all synthesizers described on this site.

PicKit to 'JNT Programming Lead Most projects on this site using PICs make use of a 4 pin in-circuit programming interface. Use this connecting lead to interface to PicKit2 and PicKit3 programmers.

Tuning control for LMX2470 and LMX2541 Rotary encoder / LCD Controller for LMX2541 and LMX2470 Synthesizers.
Tuning in 10Hz (or larger)steps, the LMX2541 version also allows the output divider to be controlled, giving a self contained tuneable synthesizer covering 40MHz upwards.

Download Complete Archive PIC code, PCB layout, higher resolution circuit diagram

The PCB is identical to that for the AD9850 rotary encoder shown above.

Verticom Synthesizer Control These Synths were originally described by G4FRE/WW2R.
Here is an alternative PIC controller to that described, that allows control with ASCII commands on an RS232 interface. Also a utility (with VB source code) for calculating the values to be sent.


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