A bias tee is a small network that injects DC power onto the coax feeding an
antenna-mounted device — typically a low-noise amplifier
— while passing the RF signal through to the receiver unaffected.1
A bias tee feeds DC up the coax to power a mast-mounted LNA while passing the RF through.
How it works
It combines a DC path and an RF path so a single cable carries both. Many SDRs (including
some RTL-SDR models) have a built-in switchable bias tee.
Relevance to SDR
A bias tee lets you power a mast-mounted LNA without a separate cable, keeping the
amplifier close to the antenna where it does the most good.
Sources
Bias tee — Wikipedia, on the RF/DC combining network that powers antenna-mounted devices over the coax. ↩
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