N3ZI DDS 2

Display showing 1Hz resolution
(0 on the left is memory number)

My first DDS has been very popular, but there have been a few requests for improved performance. The chip I chose for that design was the lowest cost chip available for the HF frequency range. The initial request for expansion was the frequency range, the first version was limited to 20MHz output, but I was able to overclock that inexpensive get to get 30MHz out.

So I have redesigned my DDS, now called DDS2, using a different DDS chip, AD9834. This has many improvements and is only slightly more expensive.
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NEW LOWER PRICES: We are now offering two versions. The FULL kit includes the PCB and all necessary components, including DDS chip, programmed microprocessor, Rotary encoder, serial LCD (show above) and LCD cable and connectors.

We also offer a BASIC version of the kit which includes everything in the FULL kit except for the DDS chip, LCD and LCD Cable. The DDS Chip (AD9834CRUZ) is required for operation, is not included in this inexpensive kit, but is frequently avaialble from the manutfacturer as a sample.

DDS Kit $73 via Paypal
Includes, DDS Kit, LCD, LCD Cable, Encoder, DDS chip

DDS Kit(DELUXE) $89.99 via Paypal
Includes, DDS Kit, as above, Plus:

DDS Chip soldered down to board

OPTICAL Encoder and Pushbutton switch, in lieu of Standard Encoder

EEPROM Fully configurered for optical encoder

DDS Kit (Basic) $49.99 via Paypal
Includes, Basic DDS Kit
NO Encoder, No LCD, No LCD Cable, No DDS chip

DDS Chip (AD9834CRUZ) is required but not included in the basic kit. It is frequently avaialbe as a sample from the manufacturer.
PayPal will add Shipping at checkout

NEW Optical Encoder Now Available

Mounting hardware

Also look at the NEW Crystal Bank Replacement DDS Kit, here

Info on firmware updates

Significant Improvements:

1) 1Hz step size. This was the most requested improvement, and this chip has it. Furthermore the LCD will display the frequency with 1 Hz resolution. I'm going to set the step size to something higher than that, but those of you who demand precision will be able to change the default step size. The LCD display will show 9 digits of frequency (a sign, 2 megahertz digits, 3 kilohertz digits, and 3 Hz digits.

2) No (or very little) overclocking. All these kits will be shipped with 80MHz clock modules. This along with an improved output filter will allow operation up to 34MHz.

3) Fast RIT and FSK. This chip has two frequency registers, and there is a direct connection to select between the two. Switching is instantaneous and phase continuous, you can use it with CW QSK and even FSK (RTTY) is you want. The push switch on the rotary encoder allows you to set the RIT offset, tuning speed, and calibration.

4) Vastly improved Encoder tuning. The dial now operates much like an analog VFO dial. I have an acceleration algorithm that works very nicely, so the push switch for speedup is no longer required. New debounce and other changes make the action smooth like an optical encoder using an inexpensive mechanical encoder. There is no lag for the LCD, and no queuing, no glitches, and catch-up.

5) Phase continuos frequency changes. The old chip had to be turned off then back on for a frequency change. So there was a brief but noticeable glitch. The new chip has phase continuous frequency changes meaning than the instant a new frequency is selected, the output waveform continues smoothly by sloping and the proper rate for the new frequency

Features and Specifications:

1Hz user tuning steps

User settable rate via tuning knob
0.3Hz internal step size.

Glitch free, phase continuous tuning.

Virtually indistinguishable from an analog VFO

Very fast tuning updates

100x faster than my previous DDS

User friendly auto acceleration, with user adjustable parameters.

Advanced debounce and tuning algorithms make the supplied mechanical encoder feel like optical encoder.

User tweekable parameters to accomdate other encoders

Very fast RIT frequency shift

Better than 1ms frequency shift time
Can be used for QSK or FSK/RTTY
Shift amount settable via tuning dial.

Complete DDS kit

Just plug it in, turn the dial, and outcomes your VFO signal.

No computer needed. No Frequency counter required.

A digital display is part of the DDS FULL Kit, and gives you full frequency readout

Full precision LCD frequency readout to 1Hz resolution

Serial LCD included in the kit
Works with 3rd party LCDs including backlit LCDs More info

80MHz reference included

Fast easy to use, user calibration, push then knob then zero beat to a reference

Digital calibration in extremely fine 1ppb steps. (ppb=parts per billion)

Maximum output frequency of 34MHz

Microprocessor does not limit upper frequency

Frequencies up to 39MHz will work, but with incresed mirror spur

DDS SPECIFICATIONS

Total Harmonic Distortion: -66db dBcf

Mirror Spur supression -60 db to 30MHz, -45 db to 34MHz.
Spurious-Free Dynamic Range (SFDR)

Wide Band (0 to Nyquist) -60 dBc
Narrow Band (±200 kHz) -74 dBc
Performance details

Main output is a filtered sine wave

250mV p-p, when driving 1K load.

Secondary unfiltered analog output

Supports IF+VFO, IF-VFO, and VFO-IF radios.

Expands the frequency coverage of many radios.

Only 1 surface mount part, 20 Pin TSSOP (AD9834)

Solder it yourself, it's easier than you think.
Kitbuilders will do it for $10

Requires 9 to 15 volt DC supply, approx. 50mA, more if a backlit display is used.
10 Memories plus A/B VFO all with their own IF offset setting.

Separate A/B VFO input signal line.

Separate RIT memory & control

IF offsets settable via RS-232 or LCD/Button/Dial

Easy to set RIT from tuing knob

Normal range +/-9.999KHz (1Hz steps)

But can be set up +/-9.999MHz for special applications

Non volatile memory storage of last operating frequency and all memories/IF's
Front Panel components can be remoted (LCD, Rotary Encoder, Buttons)
Top quaility commercial PCB with Separate Analog and Digital ground planes for best output purity.
12v RS-232 port available for setup and debug Interface Manual

Not required for operation

USB possible using inexpensive 3rd party adaptor.
(I have tested several adaptors off of ebay, with both windows and Linux, and they all work fine)

Feature	DDS	DDS2
Maximum Output Frequency	20 or 30 MHz	34MHz
Step Size	10Hz	1Hz
LCD Display Resolution	100Hz	1Hz
Tuning Speed	500ms per step	Instantaneous
RIT	None	+/- 1Hz to +/- 10MHz
QSK support	No	Yes
LCD update lag	500ms	not perceivable.
Cost	$50 to $70	$73 (FULL kit, including PCB, programmed Micro, DDS chip, LCD/Cable and Encoder)
Tuning	Discontinuous (glitch)	Phase continuous (no glitch)
Number of Surface mount parts	1 16Pin TSSOP	1 20Pin TSSOP
Memories	10	10
A/B VFO	Yes	Yes
FSK and PSK support	None	Yes
LCD Included	Yes	Yes
Works with 3rd party LCDs	Yes	Yes
Encoder Included	Yes	Yes
Chip Used	AD5932	AD9834
Optical Encoder	Optional	Optional