This is a spectrum analyzer I built. This test instrument is based on
the "Poor Man's Spectrum Analyzer" originally designed by Murray Barlowe, WA2PZO, and
presented in the September 1986 issue of HAM RADIO magazine. I purchased the
VHF "cable ready" tuner and the VHF/UHF tuner (the VHF section is not used) from
Science Workshop (WA2PZO) and placed them in a single enclosure shown in the
photo. I added a sawtooth generator for the frequency sweep described by Joe Carr in the
September 1987 issue of HAM Radio magazine. The spectrum analyzer uses an oscilloscope
for the display and can display the spectrum from 1 to 900 MHz in two ranges.
The resolution is selectable to be 250, 56 or 15 kHz. A spectrum trace of the commercial
FM band here in Huntsville from the oscilloscope is shown in the figure below.
I added an AFC so I could use this instrument as an FM radio. There is an AFC
on/off switch at the top center of the front and a volume control on the right.
I wanted to add other features such as a calibrated display (amplitude and frequency),
programmable start and stop frequencies, and the capability to plot the spectrum display.
To do this, I developed an interface to my personal computer. When I completed
this design, I published it in the premier issue of Communications Quarterly magazine
shown below. The title of the article is "Interface Your Computer to the 'Poor Man's
Spectrum Analyzer'." The first page of the article is also shown below. I have
received much interest in the article, some from overseas including New Zealand and
When the article was published, there was an error introduced into Figure 4. One
person who called me found the error. The corrected schematic is shown below. The
error involves pins 8 and 12 on U4C and U4D, respectively. Those pins go to the
B side of the edge connector, pin 13.
Since then, WA2PZO has republished my article in his own publication, "
Build Your Own Spectrum Analyzer", shown below.
If you would like to order the book, tuners, and other parts to build a spectrum analyzer like mine,
click on the link below to visit the website of Science Workshop.