Keysight-Agilent-HP 5350B Frequency Counter
This is used HP 5350B Frequency Counter in the photographs below you can see it being used on our test bench measuring the output from an Advantech L-Band to C-Band up converter.
Our engineer explained why he preferred to use the output from the HP 5350B Frequency Counter instead of measurement using a spectrum analyzer. The frequency counter is designed to provide much greater accuracy even down a few hertz. When tuning a local oscillator or other reference frequency, measurement accuracy is essential.
This HP 5350B Frequency Counter is a perfect example, it must be more than 20 years old, but it works perfectly, and so why buy another one if your tests fall between 10 Hz and 46 GHz?