Because I had to use the ADF4351 board for my new BATC Portsdown DATV project, I decided to rebuild the ADF4351 VFO with a ADF5355 module, bought from e-bay. I also replaced the PIC by an Arduino Nano. The software (sketch) is based on the design of F6KBF and F1CJN. I have replaced the push buttons in the design by two encoders and I have added a menu.
The frequency range is automatically split over two output SMA connectors: 54-6800 MHz and 6800-13600 MHz
The VFO is menu driven and has the following functions:
– Selection of one of ten memory locations
– Stepsize selection ( 1, 10, 100Hz, 1, 10 100 KHz and 1 MHz)
– Output power: -4, -1, +2, +5 dBm
– Reference input frequency 25 or 10 MHz
You can reach the menu functions by pressing the right encoder.
The last used frequency is automatic saved after 5 seconds of not tuning.
With the encoders you can tune at 100 MHz steps (left encoder) or at the selected stepsize (right encoder). But you can select the different menu functions as well.
The price of the board is much more expensive then a year ago (Thanks to Mr. Trump??). It increases from $66 to over $100!!
Using the ADF5355 module it’s very easy to build the VFO.
Because the ADF5355 is using 3.3Volt I/O you have to pull-down the output of the Arduino Nano 5Volt I/O by voltage dividers (see the schematic).
Programming can be done with the Arduino IDE and the Arduino Nano USB bus.
I have replaced the original X-tal oscillator by a TCXO for a better frequency stability. See: https://www.digikey.nl/product-detail/en/connor-winfield/DV75C-025.0M/CW885CT-ND/5641655
Using an external ref. frequency you have to remove R10 and add R17 (at least on my board). Both are 0 ohm.
Caution: The total supply current is (depending on the RF divider and output power) between 160 and 250 mA. For that reason I added an aluminum cool block on the ADF5355 and I added a separate 6V regulator as well (mounted in the middle of the back panel of the enclosure).