THE RADIO UNDERNEATH
Most long-range radios have to take turns: talk, stop, listen. Rogue and Repeater each carry two LoRa radios on two frequencies, so one can send while the other keeps listening. Here's how that works, what it changes on a mesh, and what it doesn't.
ONE RADIO VS TWO
Alias runs on LoRa, a long-range radio technology built to carry a signal for miles on very little power, over license-free bands. Most LoRa radios are half-duplex: a single radio that can talk or listen, but never both at once. Rogue and Repeater use FDD (frequency-division duplex) with two separate radio chips, each with its own connection to the processor. So one transmits on one frequency while the other receives on another, at the same time.
TYPICAL LoRa · HALF-DUPLEX
ONE RADIO
One radio, one frequency. Talk, stop, switch, listen. Every reply waits its turn.
ROGUE & REPEATER · FDD LoRa
RADIO 1
RADIO 2
Two radio chips, two frequencies, both open at the same time.
WHAT LoRa IS
LoRa spreads each transmission across a band as rising and falling tones called chirps. That lets a receiver pick out a very faint signal, and that's where the range comes from.
Semtech, the company that makes LoRa chips, rates LoRa links at up to 30 miles in rural areas. A handheld sending messages all day is a heavier load than a sensor, though, so we quote Rogue at 12+ miles typical line of sight.
LoRa trades speed for reach. A common LoRa chip tops out at 62.5 kbps. That's plenty for messages, location and status, and it's why LoRa gets through where faster radios drop out.
HOW FDD WORKS ON ALIAS
01
Rogue and Repeater each carry two LoRa radio chips. One's set to transmit on one frequency, and the other's set to receive on a second one.
02
Each chip has its own connection to the processor, so the device can hand the transmitter a new message while the receiver's still bringing one in.
03
Sending and receiving at once only works if the transmitter doesn't drown out the receiver right beside it. FDD systems keep the two frequencies apart and filter each path, so the receiver can still hear faint signals.
BOTH DIRECTIONS AT ONCE
An incoming message never has to wait for the radio to finish talking.
LESS WAITING PER HOP
When a Repeater relays your message, one radio passes it on while the other keeps listening. That means less waiting at every hop than with a half-duplex relay, which has to stop listening every time it transmits.
LONG RANGE, LOW POWER
LoRa's chirp spread spectrum is built for distance on a small battery budget: 12+ miles typical line of sight on Rogue.
STRAIGHT ANSWERS
Hills, buildings and thick trees shorten any radio link, FDD or not. The 12+ mile figure for Rogue is typical line of sight. If you want to reach farther, put a Repeater on high ground.
Two radios let messages move in both directions at once, but each link still runs at LoRa data rates, which are low next to Wi-Fi or cellular. FDD doesn't turn LoRa into broadband.
Your messages are encrypted end to end on the device before they ever reach either radio. FDD changes how quickly messages move, not who can read them.
SOURCES: Semtech, What is LoRa? · Semtech, SX1262 LoRa transceiver · Semtech, full-duplex LoRa reference design · Duplex (telecommunications), FDD
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