Thursday, March 16, 2017

Spectrum Analyzer display and control board

I gave a lot of consideration to the size I wanted for the finished instrument, and designed and printed a first try at a partially 3D printed case.  It consists of printed sides with guides for the top and bottom , which will be made from circuit board material.  I also added a guide in center for most of the RF part of the S.A. The first thing I need to build is the control and display board.  This will have the STM32 board, the display, a AD8307 power meter, and a Adafruit Si5351 PLL board. This will first be used as a SNA to help in the alignment of the filters in the RF board as it is assembled.  I should be able to use much of the software from the SNA Jr., and later may be refined into a version 3 of the SNA Jr.

The board is double sided, with the top being mostly a ground plane.  I did some playing around with different methods of adding a solder mask to the board. I refined my earlier procedure using IR curable paint, and am very happy with the results I was able to obtain.   This will make it much easier when it comes to building the RF board, which will be some of the  tightest SMD layout I have ever tried.

After assembling the board, and doing a quick functionality test, most everything worked as expected. I did have to add a jumper on the board to bring 5 volts out to the Joystick, and found I will have to make a couple slight changes in positioning some of the connectors on the final board.  But, this will be adequate for testing, and writing the SNA software.
I cutout a opening for the display , and added a cutout for the Joystick in a piece of copper clad board.  Then mounted the board and display, and installed the assembly in the 3D printed case.
Looks like everything will fit, but may have to change some of the dimensions a little and reposition the guides for the RF circuit board.
Now to write the SNA software and do the layout for the RF board.
Shouldn't take too long, unless I spend too much time playing with the 3D printers.