The Portapack is an add on for the HackRF SDR that allows the HackRF to be used portably without a PC. If you're interested, in the past we reviewed the Portapack with the Havok firmware, which enables many TX features such as POCSAG transmissions as well as various other RX modes.
In a recent video Tech Minds reviews a Portapack clone, which is essentially exactly the same as the original Portapack. In the video he shows how to connect the Portapack to the HackRF, how download the Firmware and flash it to the HackRF. He then goes on to show some of the Portapack RX features in action. In this review he uses the official Portapack firmware, but notes that he will test the third party Havok and Mayhem firmware which have many more features in a future video.