2.1 pF at 28 V — the tuning anchor
The BB135,115 is an NXP UHF varactor diode in a SOD-323 surface-mount package. Its headline parametric is a capacitance of 2.1 pF at a reverse voltage of 28 V (measured at 1 MHz), with a capacitance ratio of 12 from 0.5 V to 28 V. That ratio defines the usable tuning range for VCOs, phase-locked loops, and voltage-controlled filters in the UHF band.
30 V peak reverse — headroom for RF bias
Peak reverse voltage is rated at 30 V, which gives comfortable margin for 12 V or 24 V bias rails common in RF front-ends. The single-diode configuration keeps the parasitic inductance low — critical when the varactor sits in the tank circuit of a UHF oscillator.
That military-grade range means this varactor can live in outdoor telecom enclosures, engine-bay RF modules, or avionics receiver front-ends without the capacitance drift that commercial-grade parts show at temperature extremes.