N3ZI dds super fine tuning - 1HZ steps

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N3ZI dds super fine tuning - 1HZ steps - 34MHZ complete

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.
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.
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
* User settable rate via tuning knob
* 0.3Hz internal step size.
* Glitch free, phase continuous tuning.
* Virtually indistinguishable from an analog VFO
* 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 accommodate 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 including LCD and Encoder
* Just plug it in, turn the dial, and outcomes your VFO signal.
* No computer needed. No Frequency counter required.
* Full precision LCD frequency readout included 1Hz resolution
* User can Substitute 3rd party LCD Modules, including support for Displays w/ Backlight
* 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 increased mirror spur
* Total Harmonic Distortion: -60db dBcf
* Spur suppression -60 db to 30MHz, -45 db to 34MHz.
* Spurious-Free Dynamic Range (SFDR)
* Wide Band (0 to Nyquist) -56 dBc
* Narrow Band ( 200 kHz) -74 dBc
* Main output is a filtered sine wave
* 250mV p-p, when driving 1K load.
* Secondary unfiltered analog output
* 5v Digital square wave output also available
* 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
* Not required for operation
* USB possible using inexpensive 3rd party adapter.
This is a kit, you must know how to solder and should have prior kit building experience.