Overview
Your antenna is the most critical factor in achieving reliable range and network coverage. A well-placed antenna can increase your effective range by 5–10x compared to poor placement. This guide covers antenna positioning, types, and troubleshooting.
Antenna Basics
Types of Antennas
Omnidirectional (Duck/Whip)
- Radiates equally in all horizontal directions
- Best for nodes in the center of coverage area
- Most common for HRMesh applications
- Typical gain: 0–3 dBi
Directional (Yagi/Patch)
- Focuses signal in one direction
- Best for long-distance point-to-point links
- Higher gain but narrower coverage pattern
- Typical gain: 5–12 dBi
Panel Antennas
- Directional with wider beam width
- Good for covering large areas from a central location
- Often used on repeater stations
- Typical gain: 6–10 dBi
For community networks, omnidirectional antennas are recommended because mesh networks benefit from nodes sending in all directions.
Placement Principles
Vertical vs. Horizontal Orientation
Vertical (upright) orientation:
- Best for general coverage
- Provides 360° horizontal radiation pattern
- Recommended for most deployments
- Works well at all distances
Horizontal (flat) orientation:
- Creates a donut pattern (poor at zenith)
- Only recommended for specific long-distance links
- Not ideal for mesh networks
✓ Always mount antennas vertically for HRMesh.
Height Matters
LoRa signal travels in straight lines and is blocked by buildings and terrain. Height is one of the best ways to extend range:
| Height | Typical Range | Use Case |
|---|---|---|
| 2–3 m | 1–3 km | Portable node in hand |
| 5–7 m | 3–8 km | Rooftop installation |
| 10+ m | 8–20 km | Repeater on pole or tower |
| 20+ m | 15–40 km | Professional repeater |
Target: Mount antennas at least 10 feet (3 m) high. Higher is better.
Avoiding Obstructions
LoRa waves are blocked by:
- Large metal objects (water towers, structural steel)
- Dense vegetation (thick trees, forests)
- Buildings and concrete
- Ground clutter (rocks, dense bushes)
Best practice: Mount antennas with clear line of sight to the horizon, at least 10 feet above nearby obstacles.
Installation Guide
1. Choose Your Location
Look for:
- ✓ Highest point available (rooftop, pole, tower)
- ✓ Clear horizon in at least 270° of directions
- ✓ Away from large metal objects
- ✓ Away from dense vegetation
- ✓ Protected from high winds (if possible)
Avoid:
- ✗ Narrow valleys or canyons
- ✗ Dense urban areas with many metal buildings (though some coverage is better than none)
- ✗ Inside metal enclosures or under metal roofs
2. Mounting Hardware
Ensure mechanical stability:
Antenna
↓
SMA Connector (hand-tight + 1/4 turn)
↓
Pole Clamp (with rubber padding)
↓
Mounting Pole (1–2" diameter)
↓
Roof Mount or Wall Bracket
Important:
- Use stainless steel hardware for outdoor installations
- Pad clamps with rubber to prevent antenna rotation
- Ensure clamp tightness is firm but not over-torqued (risk of breaking SMA connector)
3. Cable Routing
- Use low-loss coax cable (LMR-400, RG-8, or better)
- Minimize cable length between antenna and radio
- Every 3 feet of coax adds ~1 dB of loss (reduces range ~10%)
- Use cable glands and conduit for weather protection
- Seal all connectors with waterproof caps or silicone
Quick loss reference:
- RG-58 (thin): ~3 dB per 100 ft @ 900 MHz
- LMR-240: ~1.5 dB per 100 ft @ 900 MHz
- LMR-400: ~0.8 dB per 100 ft @ 900 MHz
Longer installations should use heavier cable.
4. Connector Care
- Screw antenna onto SMA jack hand-tight, then 1/4 turn additional
- Over-tightening breaks the connector
- Under-tightening causes signal loss and intermittent connections
- Check connectors monthly for corrosion
- Apply dielectric grease to outdoor connectors
Testing and Validation
Before Deployment
- Bench test: Verify the node powers on and communicates nearby
- Temporary placement: Mount antenna at proposed height for 24–48 hours
- Monitor signal: Check RSSI (Received Signal Strength) from known nodes
- Log results: Document distance from nearest repeater and signal strength
After Deployment
Check signal quality at least once per month:
# View node status (method varies by HRMesh implementation)
# Typical metrics:
# - RSSI (Received Signal Strength Indicator): -140 to -70 dBm
# Good: -100 dBm or better
# Acceptable: -110 to -100 dBm
# Poor: below -120 dBm
Troubleshooting Weak Signal
Symptom: Node communicates but range is limited (< 1 km)
Check in order:
- Is antenna mounted vertically? (If not, rotate it)
- Is antenna at least 10 feet high? (Higher is better)
- Are there large metal objects nearby? (Move antenna)
- Is the antenna physically loose? (Tighten SMA connector)
- Is the coax cable damaged or excessively long? (Check and replace if needed)
- Is the connector corroded? (Clean or replace)
Symptom: No signal at all
- Is antenna screwed on? (Check SMA connection)
- Is antenna pointing up? (Vertical orientation required)
- Is the cable pinched or damaged? (Inspect along full length)
- Is the node powered on? (Check power LED)
- Is there a nearby repeater? (Move to test location)
Advanced: Antenna Gain and Link Budget
For repeaters or long-distance links, understanding antenna gain helps predict range:
Link Budget Formula:
Received Power (dBm) = Transmit Power (dBm)
+ TX Antenna Gain (dBi)
+ RX Antenna Gain (dBi)
- Path Loss (dB)
Path Loss @ 915 MHz, free space:
PL (dB) = 20 × log10(distance in km) + 20 × log10(frequency in MHz) + constant
Example:
- TX Power: 14 dBm (typical LoRa)
- TX Antenna Gain: 2 dBi (omnidirectional)
- RX Antenna Gain: 2 dBi
- Distance: 5 km
- Path Loss @ 5 km: ~118 dB
- Received Power: 14 + 2 + 2 - 118 = -100 dBm (good!)
If received power is below -120 dBm, the link is unreliable.
Next Steps
Resources
- LoRa Antenna Handbook (PDF)
- RF Engineering Basics
- HRMesh Community Forums for local coverage maps and suggestions