Understanding the SA200G Active Antenna: Features, Specs & Use-Cases

 

Introduction

In modern GPS, GNSS, and wireless systems, the choice of antenna can make a significant difference in signal strength, accuracy, and stability, especially in challenging environments (e.g. urban canyons, long cable runs, interference). The SA200G Active Antenna is one such option targeted at users who need active signal amplification and robust performance. In this blog, we’ll break down its features, key specifications, design considerations, and practical use-cases.

What Is an Active Antenna & Why Use It?

An active antenna is one that includes an integrated low-noise amplifier (LNA) inside or next to the antenna element. This LNA boosts the weak signal received before it travels down the cable to the receiver.

Benefits of using an active antenna like the SA200G:

• Compensate for cable loss: In long cable runs, signal degradation is significant; amplifying early helps preserve signal.
• Improve signal-to-noise ratio: A low-noise amplifier can raise weak satellite signals above noise floor.
• Filter out unwanted bands: Many active antennas include filtering to reject out-of-band interference.

However, it also demands proper power supply, careful layout, and good shielding to avoid amplifying noise or interference.

Key Features & Typical Specs (Based on SA-200 series & inferred for SA200G)

Because I could not locate a datasheet specifically labelled “SA200G,” I reference the SA-200 / SA200 series specs and assume “G” is a variant (e.g. for GNSS) with similar architecture. Use this as a guideline and verify with your manufacturer’s datasheet.

From the SA-200 specification:

• Operating frequency: Centered at 1575.42 MHz (GPS L1) ± about 1.023 MHz bandwidth
• Antenna gain: ≈ +5 dBi at zenith (at the patch element)
• Amplifier gain: ~ 28 dB typical
• Noise figure: ≤ 1.8 dB in LNA
• Output VSWR: ≤ 1.5:1
• Axial ratio (circular polarization): ≤ 3 dB (for circular polarization purity)
• Power supply to LNA: 4.0 to 6.0 V DC, current ~ 28 mA
• Physical construction:
• Waterproof radome (polycarbonate) with O-ring seal
• TNC connector (some variants)
• Diameter ~ 4.5 in (≈ 114 mm), height ~ 2.9 in (≈ 74 mm)
• Operating temperature: –30 °C to +85 °C
• Humidity up to 95%, fully waterproof

These values are typical for the SA-200 class. The “G” suffix might imply GNSS (including GLONASS, Galileo, etc.) support or a variation in connector or frequency range — but verify with manufacturer.

Design & Implementation Considerations

1. Cable Length & Loss

Even though the LNA boosts signal, the coaxial cable between antenna and receiver still introduces attenuation (loss). Choose low-loss coax (e.g. LMR-400, RG-213) for longer runs, and aim to keep cable length reasonable when possible. The amplifier helps, but it has limits.

2. Powering the Antenna

You must feed DC (4–6 V) to the antenna LNA. This is often done by biasing the coaxial feed (i.e. DC pass through cable). Ensure your receiver or bias-tee supports this. Also, proper decoupling and protection (e.g. RF chokes) might be needed to block interference on the power line.

3. Mounting & Orientation

• Mount the antenna where it has a clear sky view (minimal obstructions).
• Use appropriate mounts (pole, roof, mast) that minimize reflections or blockage.
• Ensure the radome is clean and has minimal obstructions (e.g. avoid metal around it).
• For marine or outdoor harsh environments, ensure the mounting hardware is corrosion resistant and grounded.

4. Polarization & Matching

The SA-200 series uses right-hand circular polarization (RHCP), which is standard in GPS. Matching polarization matters—mismatched polarization leads to signal losses. Also match the impedance (typically 50 Ω) in the system to avoid reflections.

5. Filtering & Interference

The LNA may include bandwidth limiting / out-of-band rejection to avoid amplifying interfering signals. But in environments with strong RF noise (cell towers, broadcast transmitters), additional filtering might be needed upstream or downstream.

6. Thermal / Environmental Considerations

Since the amplifier is inside, heat dissipation matters. Operating in extreme temperatures (hot roofs, direct sun) may degrade performance or shorten lifespan — ensure proper ventilation or mounting away from heat sources.

Use-Cases & Applications

Here are scenarios and systems where the SA200G (or its SA-200 class) antenna is particularly beneficial:

1. GNSS / GPS Receivers
• Vehicle tracking
• Surveying
• Precision agriculture
• Time synchronization
2. Marine & Maritime Navigation
   Because of its waterproof design and robust enclosure, this class of antennas is often used in marine environments.
3. Long Cable Runs in Buildings / Infrastructure
   E.g. placing the antenna on rooftops and routing cable through walls to indoor receivers. The LNA compensates for the loss.
4. Urban or Obstructed Environments
   In urban canyons or behind partial obstructions, the amplified signal can help maintain stronger satellite lock and better positional accuracy.
5. Telecommunications / Base Station Sync
   Providing precise timing signals to telecom infrastructure (e.g. synchronizing base stations).
6. IoT / Asset Tracking
   For remote sensors or assets needing GNSS positioning, especially where receiver is inside or shielded, the active antenna helps bridge the gap.

Limitations & Precautions

• Saturation / Overload: Very strong RF signals nearby (e.g. transmitters) could saturate the amplifier. Use filtering or shielding.
• Noise Pickup: Amplifier amplifies everything — including noise. Good grounding, shielding, and layout matter.
• Power Dependency: If the power to the LNA fails, the antenna reverts to passive (or ceases to function).
• Cost: Active antennas are more expensive than passive ones. For short-run, unobstructed installations, a passive antenna might suffice.
• Temperature Drift: In extreme conditions, the amplifier parameters can deviate.

Conclusion

The SA200G Active Antenna, based on the SA-200 family architecture, is a strong choice when your GPS or GNSS application demands amplified signal at the antenna side — especially with long cable runs, obstructed environments, or precision timing needs. Its integrated low-noise amplifier, waterproof build, and compact form make it versatile for outdoor, marine, and infrastructural deployments.

However, for best performance one must manage cable loss, proper power biasing, filtering, mounting, and interference — because amplifying signals is a delicate balance between benefit and unwanted noise.