HP8494G & HP8495G Programmable Attenuator



Programmable attenuator using HP8494G (11dB) and HP8495G (70dB). Both stepped attenuators are controlled using Atmega168 (328) uC and ULN2003 coil driver. Attenuation value is displayed by 2 digits LED commun cathode or anode.
Attenuation is adjusted between 0dB...81dB by 1dB step. Input power must to be less than 1W (30dBm), DC component max. +/-7Vdc or better avoid DC input, up to 4GHz. Insertion loss during bypass is 0.3dB/145MHz and 0.8dB/1.5GHz.
The attenuator can be bypassed by pushing encoder button, "00" flashing will be displayed. Last value is stored inside of EEPROM.

Atmega Controller Schematic v1.2
Firmware Hex
Atmega168 Fuse (8MHz internal)
HP849x Datasheet
View inside


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