Your breath won’t be the only cool thing to come from this Altoids tin.
A network analyzer is an instrument that is typically used to measure the parameters of electrical networks. These analyzers are often used to characterize two-port networks such as amplifiers and filters, but can be utilized on networks with an arbitrary number of ports as well. However, as you can imagine, they tend to be on the pricier side.
That is unless you’re DuWayne, who has devised his own using an Arduino Nano (ATmega328), a couple of log detectors, a small screen and an AD9850 direct digital synthesis module. In addition, the Maker housed these components inside an old Altoids tin along with a network analyzer that lets a user see the bandpass of a filter.
Whereas Bill Meara has manually changed frequencies and plotted the output of devices, DuWayne’s latest creation seeks to automate the entire process. He writes, “Wow. I’ve been doing this by hand, changing the input [frequency] at 100Hz increments, measuring the output, putting the results into a spread sheet, converting to log (db), creating a graph… DuWayne makes it a lot easier.”
In order to bring this idea to life, the Maker replaced an SWR bridge that he already had in his possession with two basic diode RF probes, and changed the amplifiers so he could easily adjust the gain. One probe was used to monitor the direct output of the 9850 DDS module, while the other captured the output of the device under test.
“[I] kept the same control function as in the SWR scanner. A short push on the encoder button starts a sweep of the selected band. Holding it down for over a second cycles through the bands,” DuWayne explains.
The DDS module sends a signal to the device, which is measured by the Nano and once again when it returns from the device under test. This, of course, is all plotted on the display.
“The USB connector is available and different start and stop frequencies can be entered if needed when working with IF stages,” DuWayne adds.
Lastly, the Maker threw together a basic crystal filter using three crystals that he had lying around. He was then able to use the USB interface to set the sweep range. So far, so good. DuWayne has been pleased with the results he has obtained using the lowpass and crystal filter.
Interested in learning more? Head over to the project’s official page here.