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The DL-QRP-AG UniDDS, Universal DDS VFO
useable for most QRP Transceivers like Small Wonder Labs SW+ series, Mosquita, Sparrow
English Manual download
Order Page at QRPshop International
The DL-QRP-AG UniDDS is an universally usable DDS VFO for Monoband receiver or transceiver of all sorts of type. It is available in two different variants which differe only by frequency range and current consumption. Complete electronics finds place on a board of the size of the used 2x16 LCD displayboard and can be screwed directly on the Display board. The DDS itself and the Clock Generator are placed on a little daugher boad. This trick makes it possible to deliver ready built up and checked DDS assemblies for

The difference between the two versions are given by the used DDS Chip and the Clock Generators. In both versions the newest generation of DDS is used giving improved low current consumption and considerable low spurious.

An AD9834 is used with 24 MHz discreet Clock in version A. This combination enables DDS VFOs up to a maximum frequency of 10 MHz, the current we need is as low as 14 mA!

In version we use an AD9834 with 50 MHz Clock. This one enables VFOs up to 20 MHz at 25 mA current.

Common to both variants:

• Size only 80 x30x35mm including display

All parameters in nonvolatile memory, directly programmable by a setup menu without external computer

• Freely programmable start frequency within the specified area

• Double VFO A/B




• Scan between adjustable corner frequencies, independently of the adjusted VFO start point.

• Built-in electronics keyer. Change of the speed by external Potentiometer, speed shown in WPM on the display.

• Automatic system for backlight (disconnectable)Display. As soon as the rotary encoder is touched, backlight will be switched on. Backlight will be switched off after 2 seconds after last operation.

• 3 step rates: 10 Hz, 50 Hz, 1 kHz. Resolution of frequncy display is switched over automatically according to the chosen rate.

• Digital S metre in the display processes analogous positive AGC Voltages.

• Optional digital power and SWR in the display if the QRP Cllub Micro SWR measuring head is installed.

• Digital indication of Battery Voltage

• Set-up menu with initial program loader and automatic generated parameter sentence for standard equipment like Mosquita, sparrow, SW+, SST and many others.

IF Shift:

The UniDDS can be adjusted to all conceivable combinations of the sending and reception frequency within the given frequency range

Transmitter Receiver

DDS on final frequency DDS on final frequency = Directconversion

DDS on final frequency DDS on final frequency - IF

DDS on final frequency DDS on final frequency + IF

DDS on final frequency-IF DDS on final frequency - IF

DDS on final frequency +IF DDS on final frequency +IF

Due to this flexibility it is possible to economize some equipments by leaving out the TX Mixer.

The output level of the UniDDS is about 200 mVss. There is no Lowpassfiltre post-connected to the UniDDS, to make it as flexible as possible, so everyone has to take care to some type of filtering at the input side of his own project to keep the harmonic level low. For all QRPproject kits this has been done by QRPproject.

Set-up for standard configurations:

To make the parameter input easier for the user, the UniDDS set-up uses key number input for standard designs. The key numbers of all groups have to be added arithmetical. The sum of them can be written into the setup and the DDS controller then takes on all attitudes independently.

Group 1 Display

• 0 = 160m = 1,8.... MHz

• 1 = 80m = 3,5... MHz

• 2 = 40m = 7,... MHz

• 3 = 30m = 10,1... MHz

• 4 = 20m = 14,... MHz (Take care of maximum DDS-Frequency)

• 5 = 17m = 18,... MHz (Take care of maximum DDS-Frequency)

• 6 = 15m = 21,... MHz (Take care of maximum DDS-Frequency)

• 7 = 10m = 28,... MHz (Take care of maximum DDS-Frequency)

Group 2: VFO for RX

• 0 VFO - IF

• 8 VFO + IF (if VFO < IF)

Group 3: VFO for TX

• 0 Calculated Output during TX VFO +/- IF (with TX Mixer)

• 16 No Calculation VFO +/- ZF. VFO = Output Frequency

Gruppe 4 DDS Taktfrequenz

• 0 DDS-Clock 50Mhz (AD9834)

• 32 DDS-Clock 24Mhz (AD9833)

• 64 DDS-Clock 25Mhz (AD9833)

Group 5 Standard IF Filter Types

• 0 IF 3,999 Mhz (built from 4,000 MHz Xtals. Normaly the filterfrequency is about 1 kHz below the single Xtal frequency, can be adjusted later exactly.

• 128 IF 4,9145 Mhz (built from 4,9152 MHz Xtals)

An example:

I need a DDS for my 40m Mosquita transceiver, what do I need?

1. 40m 2

2. VFO - IF 0

3. VFO - If also in TX mode 0

4. DDS-Clock = 24Mhz 32

5. IF Xtalfilter using 4,000 MHz Xtals 0


Sum: 34


I store the number 34 into the Setup. After saving, the controler doesd an automatic reset, all parameters for my 40m Mosquita are set. My Universa DDS has become a Mosquita 40 DDS. The Display shows the 7030,00, the Initialfrequency inside the 40m band (may be changed via Setup Menue) The DDS is generating 7030-3,999=3,031 MHz which is needed to receive on 7030, if I switch to TX the DDS generates the same frequency because Mosquita is using a TX Mixer.

Fine corrections can be done in the Setup Menue. You may tune the Ckock frequency or the IF frequency if you want.

Using the UniDDS

All functions of the UniDDS are done by shatft-encoder, it´s internal switch and the telegrafie speed potentiometer.

If you press the shaft of the shaftencoder shortly, the internal switch causes a change of frequency rate in sequencial order. Everytime you power on the UniDDs it sets the rate to 50 Hz per step. Every time you shortly press the rate switch, it will switch in the next sequential rate. Rates are: 50HZ, 1kHz, 10Hz. The choosen rate is shown in the display.

Main Menue

Pressing the shaftencoder switch longer the 0,5s will switch the Microprocessor into menue mode:

Menue Item Function

0 break.

leave the menue without saving


Change VFO A <> VFO B

2 light on/off

Backlight on /off (If Menue displays ON and you press the switch, Backlight will be switched ON!

3 light auto

Time function for backlight. If on, backight will be switched on automatically everytime you change the frequency. It will swich off 2 seconds after last operation.

4 scan

A scan between frequency A and frequency B will be done. Start and End of the scan are stored in EEPROM independently from th initial frequency.


Entry of Setup menue. Pressing the shaft key during power on also enters the Setup Menue.

6 keyer

Built in elecrtonic keyer for iambic paddle ON/OFF (stored in EEPROM)

7 tune

Tx switched into TUNE mode. The Display show the SWR Digital and analog as a bar and the power digital. (Only if the Micro-SWR option is installed) SWR is shown in fine resolution between 1.0 and 2 and in coarse resolution between 2 and 9,9

8 xit1k DDS switched to XIT (Transmitter incremental tuning) exactly 1 kHz above the RX frequency. RX frequencz is shown in displaz row one, TX is shown in displaz row 3. The designer left of the frequencz changes from A/B for VFO A/B to r/x for receive and transmit. Changing the frequency now only changes the TX frequency shown in row 2 of the display.

9 xit2k

Same as before, but starts with a shift of 2 kHz.


Rit ON/OF. Upper row (row 1) of display shows RX frequency, lower row shows TX frequency. When switched to rit, the RX frequency is copied to the lower row. The display designers are switched to lower case tod indicate RIT mode.

Holding the shaftencoder switch during power on causes the controller to jum into setup.

The Setup Menue:

Standard Menue step 5 brings up the Setup menue

0 Setup break

End SETUP-Menu, causes restart

1 DDS-Clock

If the output frequency is not exactly what it should be, teh Clock frequency is not exactly what it should be. Here you can exactly adjust the clock frequency. Do this very carefully, you can misalign the DDS complete. The curser below the numbers shows which part are changed by rotating the shaft encoder. Big steps are at the left side. Pressing the Shaft encoder switch moves the cursor. If the curser is right of the numbers, you can choose save or cancel with the shaft encoder. Save will save the new number.

2 VFO-A (Hz)

Chooses initial frequency of VFO A at power on

3 VFO-B (Hz)

Chooses initial frequency of VFO B at power on

4 ZF (Hz)

Here you can choose the exactly IF. During adjustment, the DDS generates the choosen frequency, This can be very helpfully while adjusting the IF section of a receiver.

5 scan-begin

Start frequency for scan mode.

6 scan-end

End frequency for scan mode

7 S-Meter calibration (works only if positive AGC Voltage is supplied)

Point 1: Start with zero signal (Dummy load at antenna jack. Hex value of zero signal is shown in the display. pressing the shaftenncoder key leads to point 2. Apply 50 uV to Antenna jack and press the shaft encoder key. Now the processor will calculate the S-Meter curve, store it and leave the menue point.

8 VFO +/- ZF

IF Shift. + adds the IF to the VFO, - substracts the IF to the VFO

9 TX +/- ZF

On enables IF shift in TX mode also, OFF disables IF shift in TX mode

10 def. config

Base loader for the UniDDS. This Setup Point appears automatically at the very first power on, it can be choosen enytime yxou want out of the setup menue. Here you can do the complete configuration by a simple number calculated based on the description on page 7.

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