HP Agilent 5253B 50-500 MC Frequency Converter 50-500MHz BNC Counter Plug-In

HP Agilent 5253B 50-500 MC Frequency Converter 50-500MHz BNC Counter Plug-In

The HP 5253B is a frequency converter plug-in designed to extend the upper measurement range of compatible HP electronic counter systems. It accepts an input signal in the 50 to 500 megacycle (MC, equivalent to MHz) range and converts it to a lower frequency that the host counter can process and display. The front panel features a large numbered tuning dial scaled from 50 to 500 MC, an analog level meter for input signal monitoring, and a BNC input connector rated at 2V RMS maximum. The rear of the unit carries a 50-pin Amphenol-style multi-pin connector for interfacing with the host counter chassis.

Specifications & What's Included

• Model: HP 5253B
• Type: Frequency Converter Plug-In
• Frequency Range: 50–500 MC (50–500 MHz)
• Input Connector: BNC
• Maximum Input Level: 2V RMS
• Front Panel: Large 50–500 MC tuning dial, analog level/signal meter (red-green indicator)
• Rear Interface: 50-pin Amphenol-style multi-pin connector for counter chassis
• Internal Construction: Discrete component PCB (red capacitors, passive components), motor/drive mechanism for dial tuning
• Form Factor: Benchtop plug-in module, aluminum chassis with gray steel front panel
• Includes: Original cardboard box
• Manufacturer: Hewlett-Packard (HP / Agilent)

Applications

The HP 5253B was designed as a plug-in accessory for HP's electronic counter product line of the 1960s and early 1970s — most notably the HP 5245L and 5245M Electronic Counters, which used a modular plug-in architecture to extend their measurement capabilities. By inserting the 5253B into a compatible counter, users could directly measure frequencies from 50 to 500 megacycles without an external signal divider, significantly expanding the counter's useful range beyond its base capability. The term "MC" (megacycles per second) was standard HP and industry nomenclature before the SI unit "MHz" became universal in the early 1970s, so this unit is contemporaneous with that transition. The calibration sticker on this unit is dated November 1973, which helps place it in service history. Today, these plug-ins are sought by collectors and restorers of vintage HP test equipment, as well as engineers maintaining legacy HP counter setups in educational or museum contexts. The modular HP counter system was widely used in university physics labs, government electronics facilities, and commercial RF engineering environments throughout the 1960s and 1970s.