JUMA-DDS board applications

31.12.2005, modified 05.11.2007


JUMA-RX1 receiver and JUMA-TX1 transmitter DDS board can be used for variety of applications with different software. This page is for brief documentation of alternative usage and software options.

Two fellow amateurs Elja oh2bcw and Markku oh6mf are working with their own filter based SSB transceivers. Both guys asked me if JUMA-RX1 DDS board could be used as VFO for their designs. I have made software options that allow JUMA-RX1 or TX1 DDS board to be used as general purpose VFO or BFO oscillator. These software implementations are primarily done for oh6mf and oh2bcw applications. I may add functionality if need arises.



JUMA-VFO software V1.00 can be found here

Software V1.00 changes. If low band IF constant is set to 0(zero) low band tuning is not reversed. This allows board to be used as frequency source with four memories.

VFO software is primarily done for two-band use with around 9MHz IF. AD9833 DDS chip spec is still the same. Board can generate frequencies from 0 to 8 MHz.

Brief spec for JUMA-VFO v0.02 test software


- VFO select signal. Microcontroller pin #4 or J9 on TX DDS board.

- Band select J1-1. Open / +5V = 14MHz, Ground/ 0V = 3,5MHz

- Tone out, Connect J5 with capacitor to speaker or audio chain


- Two frequency memory locations for each band. 4 VFOs altogether.

- Separately settable IF frequencies for both bands.

- Frequency adjustment step selectable as in other JUMA equipment.

- 0-240mV bar graph S or power meter and battery voltage meter

- Display format. Low band 3.500.00 and high band 14000.00 (only 8 digits available for frequency display)

- Fast push of encoder switch toggle between bar graph and voltmeter displays. When encoder switch is depressed selected memory location (VFO) number is also shown.

- Long (over 2s) press of encoder switch stores all frequencies, IF setup and step setup into the microcontrollers non-volatile EEPROM memory.

- During first startup (EEPROM is empty). All VFOs are set to 5MHz DDS output, IF constants to 9 MHz.

- DDS control word is used as internal representation. Adjustment, calculations and saving to EEPROM memory are done in this format. Display is calculated from this value.

- Following logic is used for display frequency calculations.

if(low_band == 0)

disp_freq = vfo.vfos[IF] - dds_freq; // low band disp = IF - DDS


disp_freq = vfo.vfos[IF+1] + dds_freq; // high band disp = IF + DDS

- Min / max limits are evaluated from DDS frequency. Display min / max frequency depends how IF frequency is set.


Test / IF frequency setup mode:

- Test / setup mode can be entered by bolding encoder switch depressed during power up. When setup mode is selected 1MHz is displayed after startup. DDS generates 1 MHz output for reference oscillator calibration.

- In test mode DDS output is constant 1 MHz.

- Band select signal selects IF constant to be set. Display shows Cal HI or LO.

- IF frequency setup is done with encoder as any other tuning operation.

- After IF constants are set they are stored to EEPROM memory with long encoder switch push.

- Cycling power brings the DDS board back to normal operation.

- IF frequency setup limits are from 0 to 9.9MHz. Setting IF frequency to 0 display shows actual DDS output frequency.





JUMA-BFO software can be found here

Test version of BFO software is done for PIC16F88 controller. BFO software is however so small that it can be compiled to PIC16F819 chip if needed. BFO software operates without display and related components. If LCD display is connected frequency and meters are shown.

BFO frequencies are fixed in this version of test software. Frequencies are chosen for Elja’s oh2bcw transceiver project needs.

Seconf IF is 9000.0 - 8867.200 (kHz) or

132,800 kHz. Required BFO frequencies are:

1)132.800kHz + 1,500 kHz or 134,3 kHz,

2)132.800kHz - 1,500 kHz or 131,3 kHz

3)132.800 kHz

BFO frequency selection is done with J1 signals:

132.800 kHz J1-1 = open / +5V, J1-2 = don’t care

131.300 kHz J1-1 = short / 0V, J1-2 = open / +5V

134.300 kHz J1-1 = short / 0V, J1-2 = short / 0V

BFO frequency adjustment:

Connect 10k potentiometer between +5V and ground. Connect center post to J3 (S-meter connector)

Connect switch from microcontroller pin #4 to ground. VFO select switch in other JUMA products.

When switch is closed you can adjust selected BFO frequency about +/- 1000Hz.

When switch is open potentiometer does not affect to the selected BFO frequency.