| DDS
VFO KIT DESCRIPTION
The
DDS VFO is a complete AD9851 DDS, Micro controller, & 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 70MHz as this is around 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
e.g. 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.
New EME167 DDS Boards after December 2010 now include an optional reference clock input. A small MMCX socket can be soldered to the board for the external clock input. This is useful when using the DDS board to construct a PLL locked to 10MHz for microwave oscillators.
I/Q DDS
VFO KIT DESCRIPTION
The
DDS VFO is a complete AD9851 DDS, Micro controller, & basic
software to produce a simple I/Q DDS signal generator, that can also
be used as a VFO for a simple SDR I/Q Radio project. The I/Q DDS is suitable for the very popular Softrock & is easily connected to the I/Q inputs on the FST3253 switching mixer. 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 35MHz as this is the maximum DDS output of 70MHz divided by 2 to produce the I & Q outputs. 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
e.g. 9MHz I/F by setting the RX display offset by 9MHz. This is also especially useful when using with the Power SDR IF or similar software to align the LCD frequency readout with the Power SDR spectrum display. 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.
AD9851
I/Q DDS & 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 Download
DDS
VFO Ver2.3x ( Software Instructions on How to use the DDS VFO) Download
DDS
Ver 2.3x SOFTWARE
( What Will The Software Allow You To Do )
Although no problems have been found with
the final Software version 2.3x since March 2010, Mini-Kits
takes no responsibility for faults & minor glitches in the
Software supplied with Kits.
Below
are the standard specifications for the dd_synth ver2.3x 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 keypad connected to
the EME170 controller board along with the rotary encoder are used to change &
memorize the menu 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 70MHz,
( Using a 30MHz osc module & DDS x6 multiplier ). Lower frequency RF output level below 1MHz is lower due to the 10nF coupling capacitors on the DDS output filter & amplifier. Maximum output of the I/Q DDS is 35MHz.
2/
TX / RX Display readout can be offset by + 1Hz to 20GHz,
( Suitable for Repeater or I/F Offsets ).
3/
No Band Switching, or Mode switching available.
4/
Memorizes the last VFO or Memory frequency that showed on the LCD display on power up.
5/
Up to 22 Memory frequencies & settings can be programmed.
(
Depends on what options have been programmed, e.g. RX only, RX/TX
use, or RX/TX & Repeater etc ).
6/
Programmed to use a low cost EC12E Mechanical Rotary Encoder.
7/
Current Ver2 software changed to a Fixed Rate Tuning with 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.
11/ Divide by 1 Display when used with the EME167 DDS VFO Kit1, or Divide by 2 when used with the EME167 I/Q DDS Kit2, divides the DDS output frequency by 2 producing I/Q outputs, suitable for a IQ mixer.
12/ Optional Repeater Offset of RX & TX Frequencies.
WHAT
BITS DO I REQUIRED FOR MY APPLICATION
APPLICATION 1: DDS VFO KIT SUITABLE AS A SIMPLE SIGNAL GENERATOR OR LOCAL OSCILLATOR
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 KNOB01 71 Series 36mm diameter Knob & Cap to suit
EC12E
1
x OSC4 30MHz Oscillator Module
1
x 70MHz KIT ( Elliptic Low Pass Filler )
1
x LCD3 ( Black/White 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 Programmed PIC Micro with dd_synth_ver2.3x
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
APPLICATION 2: I/Q DDS KIT SUITABLE FOR A SIMPLE SDR RADIO PROJECT LIKE THE SOFTROCK
Shown
below is the complete I/Q DDS VFO Ki1t 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 KIT2 ( AD9851 DDS VFO Kit )
1
x EME170 ( AD9851 DDS Controller Kit )
1
x EME170 CONN Kit ( Connector Kit )
1
x KNOB01 71 Series 36mm diameter Knob & Cap to suit
EC12E
1
x OSC4 30MHz Oscillator Module
1
x LCD3 ( Black/White 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 Programmed PIC Micro with dd_synth_ver2.3x
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
INTEGRATING THE I/Q DDS VFO WITH THE SOFTROCK
Tony Parkes development of the Softrock should be honored by the ARRL as having one of the greatest effects ever on Ham Radio & Homebrew worldwide. Daily, new SDR designs & web pages appear on the Internet due to the very high popularity of simple SDR Radio designs. The Softrock Kits are mainly simple mono band designs to keep costs low, through to more complex multi band designs. Most have very limited coverage on most bands & generally don't have full HF band coverage.
Mini-Kits has released the AD9851 I/Q DDS VFO Kit that can be easily connected to the Softrock Kits, & allows coverage of the complete HF bands to 35MHz. The software has been kept simple, & the description of what it can do can be read here.
TO CONNECT THE I/Q DDS TO THE SOFTROCK: Reference is to the Softrock RX/TXv6.2, but is similar on others.
1. Disconnect the original clock signals to the FST3253 mixer ( U7 ) on pins 2 & 14 by cutting the PCB tracks to the 74HC74 chip, ( U6 ).
2. Disconnect the X1 or X2 crystals from the onboard oscillator by remove the shorting link on JP2 used to select crystals.
3. Using a short length of 4 way ribbon cable from the ( C3 ) connection on the EME167 DDS board, connect the I-LO output ( C3 ) to pin 2 of the FST3253 ( U7 ). Connect the Q-LO output ( C3 ) to pin 14 of the FST3253 ( U7 ). Finally connect the GND connection ( C3 ) to the ground-plane close to pin 8 of the FST3253 ( U7 ).
4. You can continue to use your favorite sound card software like Power SDR IF Stage, or similar for demodulating the I & Q signals.
DDS
VFO KIT CONSTRUCTORS ALERT
1/ Be very careful when connecting the EME167 board to the EME170 controller Kit. If you connect the ribbon cable on the IDC headers the wrong way around the DDS & or PIC controller could be damaged. Please refer to the DDS VFO Block diagram that shows from which direction the ribbon cable is connected between the boards. The Ribbon cable should always be kept very short & never be routed over the top of the EME167 DDS board. The IDC headers key ways should be positioned as per the block diagram to avoid mistakes. The Key way in no way is used to identify Pin 1 of the header.
KIT
FAULTS & MODIFICATIONS
There are no Reported Faults or modifications.
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This
and all subsequent pages copyright 2001 - 2010 by Mini-Kits
All rights reserved
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Saturday
14th January 2012
