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DDS-60 Kit
A 1-60 MHz coverage VFO with built-in amplifier and variable output level from 0 to 4V p-p.
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DDS-60 Kit
A 1-60 MHz coverage VFO with built-in amplifier and variable output level from 0 to 4V p-p. |
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| Overview | Schematic | Ordering | Availability | Ways to Use |
| Assembly & User Manual | Quick Assy Guide | Builder's Notes |
Article: "Working with Surface Mount Technology (SMT) Parts"
Tech Topic: DDS-60 Spectral Purity Study
Tech Topic: DDS-60 Temperature Analysis
Order an AD9851 DDS chip with your DDS-60 Kit
Order the Assembled & Tested DDS-60 Daughtercard!
NEW Order the Bare PC Board and experiment! NEW
Overview
A number of years ago we introduced the original DDS
Daughtercard (www.njqrp.org/dds) to
the QRP community, providing a low cost and modular way to add a
precisely-adjustable 0-30 MHz signal generator to one's project. All you had to
do was add an AD9850 DDS chip and +12V, and then any number of popular microcontrollers
could control the DDS Daughtercard to have it serve as a rock-solid VFO.
Over 1,000 of these little cards were sold!
Well, there is still a demand for this inexpensive kit and an
ever-growing list of uses for it so we updated the basic design and are now
ready to provide the new_and_improved DDS-60
daughtercard. This
self-contained functional module generates a good-quality RF signal from 1-60
MHz by using a small pc board to
contain just the bare DDS essentials an Analog Devices AD9851 DDS
chip, a clock oscillator, a 5th-order
elliptic filter and an adjustable-level RF amplifier.
Additionally, an onboard 5V regulator is provided so you only
need provide a battery or power supply ranging anywhere from 8-12V
DC. The three digital control lines, the power supply, and the
output signal are all available on a pin header at the board edge, and
the DDS-60 is pin-compatible with the original DDS Daughtercard. The
schematic is shown below on this page.
The 8-position pin header at the board edge serves to allow DDS-60 to be plugged into and used in any project you might have on your
bench, regardless of which microcontroller is employed. Just provide a single
strip socket (e.g., a 16-pin IC socket split lengthwise) on the project board
and plug in the DDS Daughtercard. Heck, you dont even need a dedicated
microcontroller use a cable connected to the parallel printer port of your
PC and use public domain PC software to control the DDS board!
See the Ways to Use
section for a number of custom
solutions for you to easily control your DDS-60 daughtercard.
Once your controller-of-choice serially loads the 40-bit control word
into the DDS, the raw waveform is presented to an elliptic filter that removes
unwanted high-end frequency components, resulting in a signal of sufficient
quality to serve as a local oscillator for a transceiver. We regularly see great
signal quality, with harmonic content down to about 40 dB.
The signal generated by the DDS chip itself is quite small so we use an AD8008 low power amplifier to provide about 18 dB of gain to boost the signal to almost 4V p-p, which is 40 mW or about +16 dBm into a 50-ohm load ... quite usable in a variety of applications. This amplifier chip replaces the single-chip MMIC amps used in earlier versions of the DDS Daughtercard. The amplifier offers unconditionally stability (k>1) and yields spectrally-clean signals with harmonics down about 40 dB. It is an ideal signal source for making impedance measurements in the Micro908 Antenna Analyst and other demanding designs. A trimpot allows precise setting of desired output levels.
The amplified signal is
then presented to P1 pin 6 on the pin header where it can be used as a 50-ohm
source input signal. If not used as an input to any other component or module,
the output should be terminated with a 50-ohm resistor in order for the stated
specifications to be realized.
Specifications
ุ
Power
requirements: 8-12V DC at 130 ma (typical).
ุ
RF
Output fully adjustable to +16 dBm, or about 4V p-p into a 50-ohm load.
ุ
Output
signal not affected by varying +V supply voltage great for battery
operation.
ุ
Near-constant
output level from 1-60 MHz. (1.8 dB droop due to sinx/x sampling theorem)
ุ
Good
signal purity harmonics down approximately 40 dB from the fundamental.
ุ
Pin-compatible
with the original DDS-30 Daughtercard module (Easy
changes to the AD9850 software drivers.)
(Download
full-resolution PDF version of the schematic)
So, what can you do with
the "DDS-60 daughtercard"?
There are many ways for you to use
the DDS-60. For example, all you need to do is combine it
with your favorite microcontroller project to form a high-quality VFO.
Click here to see many ideas!
Order
the AD9851 DDS chip
The AD9851 DDS
chip used to be available as a free sample from Analog Devices, but with the
current economy they have stopped providing this valuable service for hobbyists.
However to help everyone get the DDS chip at the lowest possible price, we bulk
purchased some and we're making them available at our cost.
This means that you are getting a great deal when ordering the DDS-60 Kit and
a DDS
chip. See the DDS chip ordering information in the section below.
Remember, that we're only making this deal available for those purchasing a
DDS-60 Kit. We're not a redistributor of the chips, but we're making them
available below cost as a convenience to our DDS-60 Kit customers. One
chip may be purchased with each DDS-60 Kit. If you wish to buy more,
they are available at Digi-Key for about $24 each, plus shipping. (http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=AD9851BRSZ-ND)
Order an
Assembled & Tested DDS-60 Daughtercard!
We
are now able to provide a fully assembled and tested version of the DDS-60
Daughtercard. This includes, of course, the DDS chip on the board.
Order a bare PC Board
... and experiment!
The pc
board is laid out to allow flexible use (and re-use). The pads for the DDS chip
(top) and the reference clock (bottom) are located at one end of the board, the
LPF (top) and voltage regulator (bottom) are in the middle, and the amplifier is
at the other end. Thus, your options for experimenting could be ...
- get the bare pcb, cut off the left end and you have a 1x1 DDS chip proto
board (with or without the ref osc);
- get the bare pcb, cut off the left and middle, and you have a DDS chip + ref
osc + LPF proto board;
- get the bare pcb, cut off the right side and you have a nicely-balanced
BW-gain product amplifier (18 dB gain, adjustable 0-4Vpp into 50 ohms);
- get the kit (and optionally provided DDS chip) and experiment with the parts
as desired;
- get the fully assembled & tested DDS card, and slice & dice to suit your
needs.
These are just some ideas. Homebrewers have been doing some pretty ingenious things with the DDS-60 card over the years.
We have lots of DDS-60 Kits and AD9851 DDS chips in stock and ready to ship. You can place an order electronically through PayPal, or by conventional postal mail.
Send payments electronically via PayPal using the links below.
(Shipping fees will be automatically added during PayPal checkout.)Ordering by Mail ...
Determine prices from above and add shipping ($10 for US & Canada, $17 for International).
If you live in Maryland, add state sales tax.
Write check or Money Order payable to "Midnight Design Solutions, LLC" and send to ...
Availability
In stock.
Page last updated: April 23, 2011
