LO PLL USB MAX2871 ADF4350 ADF4351

PLL documentation in PDF is here.


The frequency synthesizer module (later in text module) can be used in several operation modes:

  • Signal source controlled from the PC
  • Autonomous signal source which can generate four frequencies preprogrammed by the user
  • Beacon which can send CW text, the scan mode with up to four frequencies is also available. All beacon parameters are user programmable.

Module specifications depends of the installed synthesizer chip, see table below for the details:

Table 1. Specifications
Parameter Value
ADF4350 ADF4351 MAX2871
Frequency range, MHz 137.5..4400 35..4400 23.5..6000
Output level (not less then), dBm +10 +10 +10 *
Signal suppression in CW pauses, dB -70
Power supply voltage, V +5
Supply current, mA 150
Dimensions (L х W х H), mm 46 x 27 x 6

* Up to 4.5GHz output frequency, output level is not less then +5 dBm at higher frequencies.

The RF part of the module is basically the same as in the synthesizer module described in this article.. The new module differs by the controller and the firmware, so much more features were realized.

Please review PLL software developer notes:

Autonomous mode

The module use in autonomous mode is straightforward and simple. When the power is applied to the module it should blink five times with the LOCK led (blinking indicated that MCU and connection between the MCU and synthesizer chip is OK). The module then will start to operate according to the programmed mode of operation and SI/S2 jumpers state (see Appendix A). The LOCK led should lit if programmed frequencies are correct and module operates correctly.

In signal source mode the module will generate one of the user preprogrammed frequencies according to the S1/S2 jumpers state (see table 2).

Table 2. Frequency selection by the jumpers
Jumpers state Frequency
S1, S2 F1
S2 F2
S1 F3
Not installed F4

In beacon mode without scanning module will send the programmed text in the endless loop on the frequency selected by the S1/S2 jumpers.

In beacon mode with scanning module will send the preprogrammed text on the frequency selected by the S1/S2 jumpers, then it will switch on the next frequency and will send the text again, and so on in the endless loop. So it will send the text sequentially on the active frequencies.

The module determines S1/S2 jumpers state at the startup.

Programming and PC controlled mode

If you want to run module in the PC controlled signal source or program module parameters you need to attach the USB cable (one from the module package) to the module and plug the USB cable to the USB port of the PC (the autonomous module power supply should be switched off). The PC should find the PL2303 RS232 to USB converter and install drivers for it automatically. You can download and install driver manually from here in case of any difficulties.

When the drivers are installed plug the USB cable of the module into the PC USB port and run modules PC software SynProg (the program can be downloaded from here). You should see the following main program dialog:

PLL USB SynProg main window

Fig 1.1. SynProg main window

Select the correct chip in the «Chip» dropdown list:

SynProg synthesizer selection

Fig. 1.2. SynProg synthesizer selection

Select the correct virtual «COM port» (one assigned to the module programming cable during the drivers installation, see above) in the COM Port combobox:

SynProg virtual COM port selection

Fig. 1.3. SynProg virtual COM port selection

Press the «Connect» button.

The synthesizer control controls should become active as well as «Disconnect», «Save», «Load config» and «Save config» buttons. The parameters displayed in the program will correspond to the currently programmed values in the module:

SynProg module controls

Fig. 1.4 SynProg module controls

The module operates now in the signal source controlled from the PC mode. The frequency can be set in the «Signal Generator» — «Frequency» field. The real programmed frequency is shown just at the right of the frequency field. There is a special algorithm in the module software which programs the synthesizer chip optimally minimizing the possible frequency error. The synthesizer uses 10..15MHz PFD frequency, but it is able to achieve tuning steps as small as tens of Hz in many cases. The output level can be changed using the «Signal Generator» — «Power» dropdown list:

Changing the level of output signal

Fig. 1.5 Changing the level of output signal

The values in the list corresponds to the signal level at the output of the synthesizer chip, the real module output signal level also depends of the frequency. You can find the typical output signal values in the table 3, 4. You should avoid setting output levels which lead to overloading output amplifier (setting output levels marked with red color in tables may slightly degrade synthesizer phase noise and spurious signals level). The module change frequency and output level shortly after the values in the «Frequency» field and «Power» dropdown list in the PC software were changes.

Table 3. Typical ADF4350 based module output levels depending of frequency and output power settings
Output level settings, dBm Frequency, MHz
200 500 1000 2000 3000 4000
-4 12.8 12.5 11 7.3 7.2 6.2
-1 15.0 14.9 13.3 9.4 9.3 7.9
+2 16.1 16.5 14.9 11.1 11.2 9.5
+5 16.5 17.2 16.2 12.5 13.0 10.5
Table 4. Typical MAX2871 based module output levels depending of frequency and output power settings
Output level settings, dBm Frequency, MHz
50 100 200 500 1000 2000 3000 6000
-4 6.8 10.8 14.7 14.4 12.7 8.3 9.8 -0.5
-1 7.8 12.0 16.0 16.2 14.6 10.3 11.8 2.8
+2 8.4 12.5 16.5 17.1 16.1 12.1 13.0 4.5
+5 8.4 12.5 16.5 17.3 16.9 12.5 13.6 5.2

If you use reference oscillator with the frequency other then 10MHz you should set the correct frequency in the «Reference frequency» field.

Four frequencies for the autonomous mode are set in the «LO/Beacon frequencies» group. You can program up to four frequencies. Each frequency corresponds to one state of the S1/S2 jumpers. The frequencies and signal level are set in the same way as described above for the PC controlled signal source mode.

The beacon mode is enables by setting the «Enable beacon» checkbox, the beacon mode controls activates after the beacon mode is enabled:

PLL USB SynProg beacon controls

Fig 1.6 PLL USB SynProg beacon controls

The scan mode can be enabled by setting the «Enable scanning» checkbox. Frequencies with the Power set to Off will not be scanned. The CW transmission speed can be set in the Transmission speed field. The message text is set in the «Beacon text» field (you can program CW messages up to 100 characters length).

The English and Russian letters, digits, space and , . = / ? symbols can be used. There are also several special commands:

  • @XY sends two characters after the @ symbol without standard character pause. For example @DN will send the / symbol.
  • #xxxx sends the tone with xxxx milliseconds duration (all for digits should be always used, for example #0500 will send tone for the 500 ms)
  • &xxxx sends the pause with xxxx milliseconds duration (all for digits should be always used, for example &0400 will send pause for the 400 ms)

When all parameters for the autonomous mode are set you should save them to the module flash memory. Press the «Save» button to do it. The program will inform you if the parameters was successfully saved or there were any problems:

Saving the standalone mode settings

Fig 1.7. Saving the standalone mode settings

You can also save the configuration to the file and load it to the program later. Use «Save config» and «Load config» buttons and select the necessary file for it.

When you have finished module programming press «»Disconnect button. You can connect another module to the PC and continue, or you can finish the program by pressing «Exit» button.

Project schematics is shown on Fig. 2.1

PLL USB ADF4350 schematics

Fig 2.1 PLL USB ADF4350 schematics

Project layout is shown on Fig. 2.2

PLL USB ADF4350 layout

Fig 2.2 PLL USB ADF4350 layout

PLL USB ADF4350 based KIT is available for order.

PLL USB ADF4350 specifications

  • Based on: ADF4350
  • RF Range: 140 — 4400 MHz
  • Output power: > 10 dBm
  • TCXO stability: typ. +/- 0.5 ppm @ 10 MHz
  • PCB dimensions, mm: 45 x 28 x 6
  • Supply operation: +5 V DC at IDQ < 150 mA

KIT includes

  • 1 x LO-PLL-USB-ADF4350
  • 1 x USB cable

KITs order: e-mail logo sales@vhfdesign.com
Technical support: e-mail logo us4ici@vhfdesign.com

Check the stock availability – here.
Request for an assembly – please fill out this form.



Fig. 3.1 LO-PLL-USB-ADF4350

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