Low cost version

A project log for Handheld 3GHz Spectrum Analyzer

Includes RF detector up to 6GHz and a datalogger

roelhroelh 09/18/2014 at 21:070 Comments

Several people asked if they can buy the analyzer as a pcb or kit.

I think with more than 270 components, this will be relative expensive and/or quite difficult to assemble. I also think that for most people, the spectrum analyzer itself is the most important, and they don’t need the other features.


To make it interesting for a lot of people, the following needs to be done:

- The cost should be low. So it should be a kit.

- It will only be a spectrum analyzer

- The kit should have no more than approx. 60 components to make it easy to build.

- SMD components should not have a very fine pitch

- The ATXMEGA should come pre-programmed, so an AVRISP2 programmer is not needed.

My plan is, to make a 'bare bones' version, and offer it as a kit. But the full version with all options will also be available, perhaps only as complete device.


The bare-bones kit will contain:

- pcb with the programmed ATXMEGA

- All spectrum analyzer components

- The Si4431 (that is difficult to mount) on a pre-assembled small pcb

- connectors: SMA input, 3.5mm RS232 half duplex, connector for 5V power adapter

- on/off button (or .perhaps only a reset button)

- NO lcd and no control buttons. Operation by the PC application.

The price of the bare bones version should be below USD 100, I think.


The following components can then be mounted as an option:

- LCD with backlight, and control buttons (enables operation without PC)

- micro-SD card connector, real time clock

- battery circuits, step-up converter, charging circuit.

- Enclosure

- Firmware updates by SD-card (no programmer needed).


The barebones version will require a redesign of the pcb, aimed for easy assembly. For instance, the MBT3946 fine-pitch dual-transistors should be replaced by SOT23 single transistor types. Only a few types of resistors and capacitors should be used. The ATXMEGA has 0.8 mm pitch, that is not very difficult to mount. (It was deliberately chosen for this, I don't like soldering big 0.5mm pitched parts). The Si4012 is a 0.5mm part, but has only 10 pins, si it can be mounted without too much trouble.

It will, however, not be possible to have the barebones design ready before the next judging round of THP...