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MRF422 NPN Silicon RF Power Transistor – 150W PEP HF Final

RF Transistors and Finals • SKU RFB00012

$95.00

The MRF422 is a high-power NPN silicon RF transistor designed specifically for linear HF amplifier service from approximately 2 to 30 MHz. It was engineered for 28-volt transmitter final stages and is specified for 150 watts PEP output at 30 MHz, making it a serious RF power device rather than a general-purpose transistor. The MRF422 was used in amateur-radio and communications transmitters where high linearity, strong RF gain, and reliable operation into difficult antenna loads were important. A particularly important application is the Kenwood TS-930S, whose X56-1430-00 Final Unit uses a push-pull pair of MRF422 transistors as Q4 and Q5 in the final RF amplifier. This exact device has been individually bench tested by RF Boneyard and identified as a healthy NPN silicon BJT with zero measurable collector leakage.

HISTORICAL BACKGROUND:
The MRF422 comes from the classic era when manufacturers were replacing vacuum-tube HF finals with rugged broadband solid-state power amplifiers. Motorola's RF power transistor line became heavily used in professional communications and premium amateur-radio equipment during this transition. Kenwood selected a pair of MRF422 devices for the TS-930S final amplifier, operating them push-pull from a 28-volt supply to produce the radio's approximately 100-watt-class transmitter output with excellent linearity. Original Motorola production of the MRF422 was later discontinued, which is why genuine vintage Motorola examples became difficult and expensive restoration parts for radios such as the TS-930S and related equipment. However, the MRF422 designation itself is not obsolete today: MACOM currently lists the MRF422 as an active product and DigiKey currently lists the MACOM version as active. For an original Motorola-marked device, the accurate wording is therefore discontinued original Motorola production / hard-to-find vintage RF transistor, not that the entire MRF422 type is obsolete.