Project by VA7DB
May 2008.

This page is to document an old project done many years ago and asked for by popular demand of some ham friends. The basic project was built from many designs gleaned from the www but primarily from W7ZOI / K7TAU. Their fine circuitry lends itself to some excellent hacking possibilities. The design is for a relatively simple to build at reasonable cost Spectrum Analyzer Adapter utillizing a cheap low frequency oscillosope as the display. The unit is fully functional up to 70Mhz as detailed here. Without too much effort a new front end could be built that would enable it to work into the UHF regions, that is why I included an Input switching circuit, although till this point in time I have never got around to finishing the UHF front end module, so you would have to do that part yourself if required. The original Aug / Sept 98 articles can be seen here:

This is a shot of the front panel.

This is a shot of the Back panel.

Below is a shot of the inside of the case, with all the various modules carefully R.F. shielded and neatly installed in the most appropriate locations for functionality.

This is the 1st Local Oscillator and 1st Mixer module.

This is the 2nd Local Oscillator and 2nd Mixer assembly.

Detailed here is the 70Mhz Low Pass Filter / VHF Band Pass Filter assembly.

Here's the I.F. Plus the Log Amp Unit.

Timebase is here.

Input Attenuator (0 to 12db good up to 1.5Ghz)

Input Switching R.F. Relay (Low Freq / High Frequency) along with the camera strap that crept into the shot (oppsy :-)

Good A.C. Input Filtering is important in a Spectrum Analyzer !

DC Power Supplies.

DC Internal Power Distribution.

Crystal Calibrator.

Tracking Generator tucked beneath the 70Mhz Low Pass Filter / VHF Band Pass Filter module.

Block Circuit Overview.

- Part 1 of the original article

Part 2 of the original article

Anyone wanting information on this project, please:
Click Here

72 fr nw VA7DB

Page Last Modified 18 May 2008