What Is a Choke Ring Antenna Used For? A Technical Guide to Multipath-Resistant GNSS
A choke ring antenna is used to suppress multipath — reflected GNSS signals that corrupt positioning — so a receiver can hold stable, centimeter-level accuracy. Concentric conductive rings block signals arriving at low elevation angles, making this antenna the reference-grade choice for permanent reference stations, geodetic networks, deformation monitoring, precision agriculture, and high-accuracy surveying.
How a Choke Ring Antenna Suppresses Multipath
A choke ring antenna is a survey-grade GNSS antenna with a ground plane of concentric metal rings (typically 3–7) surrounding a central element. Each ring acts as a quarter-wave choke: it presents a high impedance at GNSS frequencies (L1, L2, L5, E1, E5, B1, B2, B3), so reflections arriving below roughly 10–15° elevation are attenuated before reaching the radiating element, while satellite signals above that horizon pass through unaffected. The result is dramatically reduced pseudorange and carrier-phase multipath. We cover the physics in depth in our companion guide, how a choke ring antenna reduces multipath.
Permanent Reference Stations and Geodetic Networks
The most common use is in permanent GNSS reference stations — the fixed base stations that broadcast RTK corrections to rovers. CORS networks, national geodetic surveys, and commercial RTK correction services deploy choke ring antennas because these stations run 24/7 in fixed locations where multipath would otherwise bias every correction they emit — and a biased base station degrades accuracy for every rover connected to it. Choke ring antennas are also standard on geodetic monuments used to define coordinate frames and track tectonic motion, where repeatability over years matters most. Pair one with a rugged RTK GNSS receiver box for a station that holds millimeter-level stability.
Deformation Monitoring and Structural Health
In deformation monitoring — dams, bridges, open-pit mine walls, landslide zones, and high-rise construction — engineers track antennas at multiple points and look for displacements of just millimeters. Multipath is the enemy: it introduces correlated errors that look like real movement. Choke ring antennas reject ground reflections so the position time series reflects actual structural motion, not daily multipath cycles from changing satellite geometry. Because construction and mining sites are also full of RF noise, these antennas are usually paired with a receiver that handles interference too — our anti-jamming and anti-spoofing GNSS receivers combine AIM+ interference mitigation with choke ring multipath immunity for a fully resilient monitoring station.
Surveying and Precision Agriculture
Surveyors use choke ring antennas on base stations for RTK and PPK campaigns, especially in built-up or reflective environments such as urban canyons, metal fences, and construction sites. Rovers can use lighter survey antennas because movement averages out multipath; the base station sits still, so multipath must be suppressed at the antenna itself. Precision agriculture is a growing use case: RTK base stations for tractors, sprayers, and robotic implements often sit at a fixed point for an entire season, surrounded by large metal machinery. A choke ring on the base keeps corrections clean so rovers hold repeatable pass-to-pass accuracy. See our full multi-frequency GNSS antennas range.
Choke Ring vs. Survey Antenna: When Do You Actually Need One?
Choke ring antennas are larger, heavier, and more expensive than compact survey antennas. You need one when the antenna is stationary for long periods, the environment is highly reflective, or you are building a base station whose errors propagate to other receivers. For moving platforms — rovers, UAVs, robots, vehicles — a compact survey-grade antenna is usually the right trade-off, paired with a Septentrio-powered GNSS board for receiver-level multipath mitigation. For drone RTK operations, weight rules out choke rings entirely; AIM+ processing and careful antenna placement handle multipath instead.
FAQ: Choke Ring Antennas
What is a choke ring antenna used for? It suppresses multipath — reflected GNSS signals that corrupt positioning — in applications that need maximum accuracy and stability: permanent reference stations, geodetic networks, deformation monitoring, precision agriculture bases, and high-accuracy surveying.
How much does multipath affect GNSS accuracy? It can cause errors of several meters in pseudorange positioning and centimeters to decimeters in RTK positioning, depending on the environment. In severe reflective conditions it also causes cycle slips and loss of fixed RTK solutions.
Do I need a choke ring antenna for RTK surveying? Not on the rover — movement averages out multipath. On a static base station, a choke ring is strongly recommended so the corrections you broadcast are not biased.
What is the difference between a choke ring and a survey antenna? A survey antenna uses a large ground plane and advanced elements to reduce multipath while staying compact. A choke ring adds concentric conductive rings that physically block low-elevation reflections, giving better rejection but a larger, heavier, more expensive form factor.
Does a choke ring antenna protect against GNSS jamming? No. Choke rings mitigate multipath, not jamming or spoofing. To survive interference, you need a receiver with AIM+ anti-jamming technology, such as Eview’s anti-jamming GNSS receivers, which maintain lock through interference that defeats standard receivers.
Can a choke ring antenna be used on a drone? Rarely — the size and weight (typically 5–10 kg with mounting) make it impractical for UAVs. Drone RTK systems use compact survey antennas and rely on receiver-level multipath mitigation and anti-jamming processing instead.
