The Right Antenna, Worn the Right Way: How to Keep Body-Worn Radios Connected
Most “bad radio days” are antenna days. Human tissue detunes antennas, metal gear shadows signals, and long or coiled cables waste power. Pick the right antenna for the band and mount it with clearance, correct polarization, a suitable ground plane, and short, low-loss cable—then tune and test on-body.
Why antenna choice and placement matter
Radios succeed or fail at the antenna. On the body, three things hurt performance:
Absorption and detuning: The body (water-rich tissue) lowers antenna resonance and efficiency.
Shadowing by metal: Tools, plates, and batteries block or reflect RF.
Cable loss/noise: Long, looped or poorly grounded leads throw away dB and invite common-mode noise.
Choose the right antenna for the job
VHF/UHF voice (public safety, marine): Vertical whip/monopole (needs a ground plane). If you can’t provide it, use a dipole or FPC (flex) antenna with its own counterpoise.
LTE/5G data/video: MIMO pair (two antennas) with separation and orthogonal orientation for diversity. Prioritise higher-gain, body-tolerant designs.
GNSS/Iridium/satcom: Patch antenna with clear sky view and correct polarisation (RHCP). Keep it high (shoulder/helmet/pack top).
LoRa/ISM: Small quarter-wave whip or tuned FPC/dipole; favour designs rated for on-body detuning.
Placement principles (that consistently work)
Give it air: Keep 5–10 mm (or more) off the body; avoid pressing under straps.
Mind polarisation: Keep VHF/UHF whips vertical; use RHCP patches for satcom/GNSS.
See the sky: Put satcom/GNSS patches on the shoulder/helmet/pack top.
Distance from metal: Keep ≥ ¼ λ from metal plates, tools, or battery bricks.
Cable discipline: Use short, low-loss coax, no tight coils, strain-relieve at both ends.
Ground plane or self-contained: If mounting a monopole, provide a proper ground plane; otherwise choose a dipole/FPC.
Separation for coexistence: Space multiple antennas by ≥ 0.5 λ; add RF filters/blanking if radios share bands.
Build and test like a pro
Match on-body: Tune with a VNA using a saline/gel phantom or the real kit worn. Target S11 < −10 dB (VSWR < 2:1) in-situ.
Walk/drive test: Log RSSI/RSRP/SINR, packet error rate, and voice quality in real routes.
Cable & connector check: Measure end-to-end loss; prefer robust connectors (SMA/TNC on externals; MMCX/U.FL internally with strain relief).
EMC & safety: Verify SAR/power limits and regional compliance (FCC/CE/RED). Keep high-duty radios away from the head/torso where feasible.
Environmental hardening: IP67/68 housings, UV-stable radomes, anti-corrosion hardware, and flexible adhesives for FPCs (avoid bending the radiating area).
Quick deployment checklist
Antenna vertical (or RHCP with sky view) and not touching the body
No metal directly behind/in front of the antenna
Cables short, uncoiled, strain-relieved, and grounded correctly
Measured VSWR < 2:1 once worn with gear
For LTE/5G, two antennas with spacing/orthogonal orientation
For satcom/GNSS, highest, clearest placement on the kit
