| DDS
VFO KIT DESCRIPTION
The
DDS VFO is a complete AD9851 DDS, Microcontroller, & basic
software to produce a simple DDS signal generator, that can also
be used as a VFO for a Radio project. Most of the functionality
is dependant on the standard software that Mini-Kits supplies
with the Kit.
The
Kit is for constructors that have some experience in soldering
SMD components, with many of the conventional sized SMD components
being easily fitted. This Kit may be a challenge for some with
soldering the AD9851 chip to the DDS board, so Mini-Kits does
offer a service at extra cost to fit just the chip, & also
can provide fully built Kits. Some wiring is needed for the header
connections between the boards, LCD & Keypad. It is suggested
that a suitable crimping tool for
2.5mm header pins be used for reliability, & to save time
The
maximum frequency that can be used is 60MHz as this is a third
of the maximum DDS clock frequency for the AD9851 chip. The software
allows for a VFO for RX, & a separate VFO for TX that can
have the VFO frequencies offset from the displayed frequency.
This is useful for receivers or transmitters with an Intermediate
Frequency, I/F. So yes it can be used on a receiver that has an
eg 9MHz I/F by setting the RX display offset by 9MHz. A number
of memories frequencies are also available for programming.
DDS
chips produce lots of outputs that although many dB under the
actual output frequency, can still produce spurious output frequencies
when directly fed into a Mixer. For this reason it is suggested
that the AD9851 DDS is suitable for simple Radio receiver &
signal generator projects. If it is to be used for higher performance
applications, then the DDS can be used a a reference for a PLL
including a separate VCO oscillator.
AD9851
DDS VFO DOCUMENTATION
The
first part is to discuss the specifications of the software so
that you can determine if any of the DDS kits are suitable for
your application.
DDS
VFO BLOCK DIAGRAM 
21/7/10 Download
DDS
VFO Ver2.20 ( Software Instructions on How to use the DDS VFO)
Download
DDS
VFO SOFTWARE
( What Will The Software Allow You To Do )
Mini-Kits
takes no responsibility for faults & minior glitches in the
Software supplied with Kits. The Software is supplied free
of charge to Mini-Kits, & no problems have been found with
the final version 2.20 since July 2009.
Below
are the standard specifications for the dd_synth ver2.2 software
supplied by Mini-Kits. The PIC Source code may be available for
those that may want to change things to suit their own application
We ask that any changes to the software be available to all other
Ham Radio operators through Mini-Kits for free.
BASIC
SOFTWARE SPECIFICATIONS
All
Software settings can be changed in the menu setting screens that
are displayed on the LCD module. The pushbuttons connected to
the DDS along with the rotary encoder are used to change &
memorize the settings into the PIC. No Reprogramming
of The PIC with a computer is required.
1/
Frequency range programmable from a minimum frequency of 1Hz,
to a Maximum output frequency of 60MHz,
( Using a 30MHz osc module & DDS x6 multiplier ).
2/
TX / RX Display readout can be offset by + or - 1Hz to 11GHz,
( Suitable for Repeater or I/F Offsets ).
3/
No Band Switching, or Mode switching available.
4/
Memorises the last VFO frequency on power up.
5/
Up to 22 Memory frequencies & settings can be programmed.
(
Depends on what options have been programmed, eg RX only, RX/TX
use, or RX/TX & Repeater etc ).
6/
Programmed to use a low cost EC12E Mechanical Rotary Encoder.
7/
Variable Rate Tuning & Adjustable Step Size 1Hz, 10Hz, 100Hz,
1kHz, 10kHz, 100kHz, 1MHz, 10MHz, 100MHz, 1GHz etc
8/
Software fine tuning of the Reference oscillator frequency.
9/
RIT ( Receive Incremental Tuning ) in RX mode only.
10/
Programmable for various Reference oscillator frequencies &
DDS x1 or x6 Multiplier.
Direct
Digital Synthesizer Experimenters Kit using an Analogue Devices
AD9851 DDS chip, which is suitable as an accurate signal generator,
or as a VFO for a RX or TX project. The chip can be directly controlled
by a computer, or by an onboard PIC 16F628 microprocessor. The
DDS output uses a L.P.F. & MAR amplifier for up to +7dBm output.
The EME85 board has connections for an LCD display for frequency
readout, & a control board with rotary encoder for frequency
control. The frequency reference can be either an onboard computer
xtal ( eg 30.000 / 100.000MHz ) oscillator module, or an external
temperature controlled high stability oscillator.
WHAT
BITS DO I REQUIRED FOR MY APPLICATION
Shown
below is the complete DDS VFO Kit1 that is used by Mini-Kits for
testing & development. The
Kit we supply does not include the aluminium chassis, hardware
or DC power connector, all other parts shown are included.
WHATS
INCLUDED IN THE DDS VFO KIT1
1
x EME167 KIT1 ( AD9851 DDS VFO Kit )
1
x EME170 ( AD9851 DDS Controller Kit )
1
x EME170 CONN Kit ( Connector Kit )
1
x KNOB2 71 Series 28mm diameter Knob & Cap to suit
EC12E
1
x OSC4 30MHz Oscillator Module
1
x 70MHz KIT ( Elliptic Low Pass Filler )
1
x LCD5 ( Blue 16x2 LCD Display Module with Backlight
)
1
x KEYPAD2 ( 16 Key Numeric Keypad 4x4 matrix )
1
x SMA33 SMA Female PCB Socket
1
x PIC16F648DDS2.2 Programmed PIC Micro with dd_synth_ver2.2
software
1
x Metre 10 Way Ribbon Cable
If
this is the DDS Hardware that suits your application,
then I would recommend that you purchase the complete
DDS VFO KIT1 from Mini-Kits which includes all the above
Click Here
DDS
VFO KIT CONSTRUCTORS ALERT
There
are no alerts at this time. For any problems with your kit, please
refer to the kit faults & modification section below.
KIT
FAULTS & MODIFICATIONS
1/
.
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