Overview

Prescaler front-end to extend the maximum frequency range on a frequency counter.

This will take a 100 - 3,500 MHz signal and divide it down 1,000 times so you can measure microwave frequencies outside the normal range of your low-cost frequency counter.  For example:  A 2,450 MHz RF input signal will read "2.450 MHz" on your counter.

This design is from Neil Eaton of Emsys Engineering, and was in the July 20, 2000 issue of EDN Magazine.  This version has a few minor modifications.

The NEC UPB1507GV prescaler IC is available from Mouser Electronics.  A Fujitsu MB506 is substituted in the pictures.

Keep the prescaler's RF input low, around 0 dBm (1 mW).  The absolute maximum is around +5 dBm (3.2 mW).

Pictures

Select a picture for larger image.

Prescaler overview.

RF input is via the top N connector and directly into the a MB506 (divide-by-128) prescaler.  The divide-by-1000 output is via the bottom BNC connector.

Alternate view.

Note there is a wiring error on the 74HC161 on the far-right.  The white wire should go to pin 2.  Pin 3 should be open.

Outside case overview showing the RF connectors, the power LED, and switch.  It's built into an old California Amplifier MMDS downconverter case and is powered by an internal 9 volt battery.

Schematic

• GBPPR Divide-by-1000 3.5 GHz Prescaler

Notes

• 2.8 GHz Prescaler Keeps Cost Down  Original EDN article.  (230k PDF)
• 13 GHz Frequency Counter Prescaler  Similar "divide-by-1000" prescaler which is good up to 13+ GHz.