Please Note the New updated EME85F PC Board supplied has now got a green solder mask

21st July 08 We are currently working a a HF Transceiver design DDS using the PIC18F4520. We hope to have a prototype running soon.

WHAT BITS DO I REQUIRE FOR MY APPLICATION?

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.

WHAT WILL THE DDS & SOFTWARE ALLOW YOU TO DO?

The Software is designed to be used for a simple signal generator, but also has if you like, 2 VFO's for RX & TX display frequency that can have the frequency display set differently from the actual DDS output frequency. This is useful for receivers or transmitters with an IF, ( Intermediate Frequency ). So yes it can be used on a receiver that has an eg 9MHz IF by setting the display offset by 9MHz. It is however not suggested that the DDS just be connected to a radios mixer without a suitable bandpass filter on the output of the DDS. DDS chips produce lots of outputs that although many dB under the actual output frequency can still mix in a radios mixer, & produce spurious output. The best way to use a DDS on a Radio is to use a 1:1 Phase Locked Loop circuit & use a separate VCO oscillator as the actual oscillator for the Radio & the DDS for the PLL's reference.

BASIC SOFTWARE SPECIFICATIONS

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 IF Offsets ).

3/ No Band Switching, or Mode switching available.

4/ Memorises the last 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 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.

Refer to the Software Notes for more detailed information & Use, Download Here

APPLICATION 1

The Minimum Component Requirement to make a DDS with an output frequency from 0 to 60MHz. The 4 x Pushbuttons are for, Step Size, Calibrate, Receiver Incremental Tuning, & Repeater. You don't have to use all 4 functions, but Step Size & Calibrate will require switches.

1 x EME85 KIT ( Basic DDS Kit )  

1 x EC12E ( Mechanical Rotary Encoder ) Requires a Knob to suit a 6mm diameter Shaft

1 x OSC 4 ( 30MHz Oscillator Module )

1 x 70MHz KIT ( 70MHz Elliptic Low Pass Filler )

1 x LCD1 ( 16x2 LCD Display Module )

4 x 1N4148 Diodes

4 x Switch5 Momentary Contact

To control the DDS circuit you will have to build the control circuit yourself.  It is so simple  to build something on a piece of veroboard, that PC Boards are not available from Mini-Kits. You will  need to buy a  few 1N4148 diodes & a few momentary pushbutton switches if you don't have some. You might even decide to mount the switches on the front panel of a project box. The minimum requirement of switches is, the Step Size & Calibrate to make a simple signal generator.  

Download Basic Ver1 Control Circuit Here

APPLICATION 2

The Minimum Component Requirement to make a DDS with an output frequency from 0 to 60MHz, with advanced features like memories & direct keypad entry. The EME129 Control Kit has 6 Pushbuttons, Step Size, Calibrate, Memory, Receiver Incremental Tuning, Repeater, & one Spare position.

1 x EME85 KIT ( Basic DDS Kit )  

1 x EC12E ( Mechanical Rotary Encoder )

1 x OSC 4 ( 30MHz Oscillator Module )

1 x 70MHz KIT ( 70MHz Elliptic Low Pass Filler )

1 x LCD1 ( 16x2 LCD Display Module )

1 x KEYPAD1 ( 12 Key Numeric Keypad 3x4 matrix )

To control the DDS circuit it is recommended that you use the EME129 Control Board Kit. If you try & build it yourself, it can be a bit complex to wire up the 16 diodes & switches correctly. The EME129 Control board circuit can be downloaded below.

Download EME129 KIT Ver2 Control Circuit Here

If this is your Application 2 above, that I recommend that you purchase the complete DDS KIT2 from Mini-Kits which includes all the above & a knob to suit the EC12E encoder.