Short answer
A coiled-wire GNSS antenna offering broader bandwidth than a patch in a similar footprint, naturally circularly polarised. Common in UAV / aviation applications where the form factor (10–30 mm diameter cylinder) fits drone arms or wing-mount sockets.
Detailed explanation
A helical antenna consists of a conducting wire wound in a helix shape around a cylindrical air or dielectric core. The geometry naturally radiates circularly polarised energy (right-hand or left-hand depending on winding direction) without needing a balun, simplifying multi-band design.
Quadrifilar (four-arm) helices are common in modern GNSS antennas — four interlaced helical windings fed with 90° phase progression, producing very clean RHCP with low axial-ratio variation across the upper hemisphere. This is the typical form factor for compact survey-grade GNSS receivers, mobile-mapping platforms, and UAV applications.
Bandwidth scales with helix pitch and number of turns. A four-band L1/L2/L5/L-band combo can be packed into a 50–80 mm cylinder — narrower footprint than a 100 mm patch antenna with comparable performance. Multipath rejection is generally better than patch but worse than choke ring.
GNSource sells helical antennas in the TDXL-800/900/HA series for survey rovers, the TDXL-LCA series for lightweight aviation / UAV, and the TDXL-S1505 four-arm spiral for BDS Tiantong satellite handsets. The choice between helical and patch is largely about bandwidth: multi-band is easier with helical, single-band is cheaper with patch.
Where you'll see this
Aviation & UAV
Browse product lineRelated terms
Patch antenna
A flat ceramic or PCB GNSS antenna with a single dielectric-loaded radiating element on a ground plane. The dominant antenna type for compact, low-cost, vehicle, and OEM applications — ranging from 18 × 18 mm pucks to 100 mm survey-grade discs.
Phase center
The apparent electrical centre of an antenna — the point from which signal range is effectively measured by a GNSS receiver. Phase-centre stability (the variation in this point as the signal arrival angle changes) is the single most important parameter for survey-grade and geodetic antennas.
Polarization (RHCP / LHCP)
The rotation direction of the electric-field vector in a GNSS signal. All GNSS satellites broadcast right-hand circularly polarised (RHCP) signals. Ground reflections flip handedness to LHCP, so an antenna that rejects LHCP automatically rejects single-bounce multipath.