Summary of The Simple Scalar Network Analyzer
This project describes a low-cost Scalar Network Analyzer (SSNA) for HF bands (1–30 MHz), designed to test filters, antennas, and cables. Built for under $20, it uses an AD9850 DDS module as a signal generator and an AD8307 chip as a power detector, controlled by an Arduino Nano. The system connects to a PC via USB for data visualization and analysis, offering a practical alternative to expensive lab equipment for amateur radio enthusiasts.
Parts used in the Simple Scalar Network Analyzer:
- Host PC
- AD9850 DDS module
- AD8307 log power detector chip
- Arduino Nano clone
- Coupling capacitors
- Lowpass filter
- Return loss bridge or coupler
After playing around with the SynthNV signal generator/power detector discussed in the previous post I realized what a useful a tool it is for RF testing. While its a terrific tool for VHF/UHF/Microwave testing, the SynthNV has a couple of serious limitations for amateur use in the HF region – the signal generator has a minimum frequency of 35 MHz, the generated signal has a lot of harmonics and its a fairly expensive piece of gear. This project is a fairly simple, very low cost Scalar Network Analyzer that does the same thing in the HF bands from 1MHz to 30MHz. If you buy the parts from China or Ebay and do some scrounging it should cost you less than $20 to build.
Video demonstration of the Simple Scalar Network Analyzer.
What is a Scalar Network Analyzer and why do you need one?
The principle is to stimulate an electrical network with a sinewave and measure the magnitude of the response. If we sweep over a range of frequencies and measure the power transmitted through the network we can determine its frequency response. Transfer from the input port (1) to the output port (2) is called the network’s S21 S-parameter response. By using a return loss bridge or coupler we can measure the reflected power – the S11 response. A Vector Network Analyzer is a much more complex piece of gear that measures the phase response of the network as well.
In practical terms, a Scalar Network Analyzer allows you to test and characterize crystal filters, attenuators, highpass/lowpass/bandpass filters, cable losses, and antennas among other things. Its also useful as a signal generator and the power detector can be used on its own for power measurements.
I make no promises as to the accuracy of this device. In my testing it does what I expect and the measurements seem very reasonable but its not a lab quality tool. It is however a fun and useful project to build and experiment with. I’m still finding uses for it!
The Hardware
The hardware for the Simple Scalar Network Analyser (SSNA) consists of a host PC which provides the user interface and a USB connected signal generator/power detector module. The signal generator is an inexpensive AD9850 DDS module which can be bought on Ebay or from a number of electronics suppliers for about $10 USD. The AD9850 chip can synthesize a fairly clean sinewave from below 1Hz to approximately 50MHz. In this application the useful range is about 1MHz to 30MHz because of the coupling capacitors and the lowpass filter used on the module. The power detector uses an Analog Devices AD8307 log power detector chip. The AD8307 has a range of -75dbm to +17dbm from DC to 500MHz. A $3 Arduino Nano clone controls the DDS and digitizes the analog output of the AD8307. The Nano has a built in USB to serial interface which is used to communicate with the host PC. The signal generator/power detector module runs off 5V USB power and consumes only 150ma from the host.
For more Details: The Simple Scalar Network Analyzer
- What frequency range does this project cover?
The device operates from 1MHz to 30MHz. - How much does it cost to build?
It costs less than $20 if parts are bought from China or eBay. - Can this device measure phase response?
No, it measures magnitude only; a Vector Network Analyzer is needed for phase. - What components control the signal generation and detection?
An AD9850 chip generates the signal and an AD8307 chip detects power. - Does the project require a specific operating system on the host PC?
The article does not specify a required operating system. - What is the primary use of the return loss bridge mentioned?
It is used to measure reflected power known as the S11 response. - How much power does the module consume from the host?
The module consumes 150ma from the host. - Is this device considered lab quality accurate?
No, the author states it is not a lab quality tool. - What types of components can be tested with this analyzer?
You can test crystal filters, attenuators, various filters, cable losses, and antennas.
