Summary of New Arduino Project: Spectrum Analyzer?
The article describes a DIY project to create a basic HF band spectrum analyzer using an Arduino and a direct digital synthesizer (DDS). The goal is to measure the difference in signal strength before and after a filter to evaluate filter performance and avoid front-end overload in receivers. The Arduino controls the DDS scanning from about 0.5 MHz to 40 MHz and reads voltage inputs from RF voltmeters connected before and after the filter. This setup offers a cost-effective alternative to commercial spectrum analyzers for ham radio enthusiasts.
Parts used in the Spectrum Analyzer Project:
- Arduino microcontroller
- Direct Digital Synthesizer (DDS) module
- RF voltmeter for input signal measurement
- RF voltmeter for output signal measurement
- RF probe(s)
- Filter under test
I’ve been reading a lot about receivers, and it sounds like one important thing is filtering. It makes sense too – simple receivers can suffer from front end overload due to a strong signal. And when on the ham bands, you never know where that strong signal may be – it could be someone driving down the road (which is a bit obvious once you see it), but in my neighborhood, if you don’t know me, you’re probably not going to know about the antennas in my attic.
I don’t have a spectrum analyzer, and since I’m a traffic engineer, I really don’t have access to one. I don’t need a full-blown spectrum analyzer, either, I just need to sweep through the HF band and get the difference between signal input and output. Math will take care of the rest.
dB=20*\log{\frac{V_{out}}{V_{in}}
The way I figure it is this:
An Arduino (and this could become a Raspberry Pi or any number of other devices, but I’m going to use an Arduino because it’s cheap and relatively durable) controls a direct digital synthesizer (DDS) module that just scans through it’s limits… well, probably something like 0.5 MHz – 40 MHz – that gets me into the AM broadcast band (which can be a source of strong signals) to above the 10m band (I don’t know what’s up there, but whatever’s there is probably not running 50,000 watts).
The output of the DDS would have an RF voltmeter and a probe to go to a filter. There would be another RF voltmeter to sense a filter output. The Arduino would handle not only control, of the DDS, but also sensing the voltage.
It’ll look something like this:
This is a block diagram/schematic of how this will work. I didn’t include the DDS module, which would be tied in there somewhere.
The Arduino and DDS will look like this:
For more detail: New Arduino Project: Spectrum Analyzer?
