How to Install External Radio on RTK GNSS: Step-by-Step Guide
External radio installation on an APEKS GNSS base station requires three precise operational steps: physical assembly of the Harxon antenna mast along with secure cable connections to a 12V external battery, configuration of the ABL90 external radio within ApekSurv (Air Baud Rate 9600, Baud Rate 38400, Protocol TT450, and Adaptive function enabled), and matching the rover's internal radio to the identical channel and protocol. Correct parameter matching between the base station and rover is the most common operational failure point—a single mismatched channel completely prevents a Fixed RTK solution.
- When to Use External Radio vs Built-in Radio
- Equipment You Need
- Step 1: Hardware Assembly — Base Station Setup
- Step 2: Cable and Power Connections
- Step 3: ApekSurv Configuration — Base Radio Settings
- Step 4: Rover Data Link Matching
- Step 5: Test and Verify Fixed Solution
- Troubleshooting: Common External Radio Failures
- FAQ
When to Use External Radio vs Built-in Radio
In high-precision RTK surveying, choosing between an internal and an external UHF radio data link directly affects your surveying efficiency and maximum operating baseline. While built-in internal radios offer maximum portability for short-range tasks, an external high-power radio is indispensable for challenging field conditions and long baselines.
Primary Deep Field Use Cases
- Extended Baselines: When the distance from the base station to the rover exceeds the typical 3–5 km internal radio limit.
- Challenging Terrain & Large Sectors: Ideal for open plains, precision agriculture, heavy mining setups, and massive infrastructure developments.
- No CORS Infrastructure: Crucial for remote or ultra-isolated exploration sectors entirely devoid of network CORS/NTRIP cell coverage.
Data Link Comparison Table
| Feature / Parameter | Built-in Internal Radio | External UHF Radio (Harxon ABL90) |
|---|---|---|
| Typical Transmission Range | 3 – 5 km | Up to 15 km (Field Verified) |
| Power Output Capacity | Typically 1W – 2W | High-power multi-watt output |
| Power Source | Internal GNSS receiver battery | External 12V heavy-duty battery |
| Primary Application | Small-scale local surveys, highly mobile urban environments | Large infrastructure, mining, precision agriculture, remote mapping |
Equipment You Need
Before heading out to the field site, ensure your instrumentation checklist contains all mandatory high-performance components to avoid signal failure:
- APEKS GNSS Receiver: Configured to act exclusively as the Base station.
- Harxon External Radio: High-power model ABL90 external UHF radio.
- Antenna Mast & Support Rod: For elevated, stable vertical placement of the transmitter antenna.
- Dedicated Data Cable: Custom heavy-duty interface cable linking the APEKS GNSS receiver to the external radio.
- 12V External Battery & Power Cable: High-voltage power line equipped with heavy alligator clips for continuous external power supply.
- Surveying Tripod: Heavy-duty platform to firmly secure the base instrumentation.
- Rover Kit: APEKS Rover receiver along with an Android field controller mounted on a stable ranging pole.
Step 1: Hardware Assembly — Base Station Setup
Open the heavy-duty yellow protective instrumentation case on site. Securely extend and plant the surveying tripod over your known control point or chosen base location, ensuring the mounting platform is level.
Mount the APEKS GNSS base receiver securely to the tripod tribrach. Assemble the external antenna support rod alongside the structure, and screw the high-gain UHF transmitting antenna vertically onto the tip. Firmly fix the Harxon ABL90 external radio housing onto a secure bracket on the tripod leg.
Step 2: Cable and Power Connections
Take the dedicated multi-pin data cable and plug it into the correct communications port of the APEKS GNSS base receiver. Route the other end of the cable safely into the data input port of the Harxon radio unit, ensuring the locking pins click home tightly.
Connect the high-voltage power line to the external power input terminal of the Harxon radio. Attach the heavy-duty color-coded alligator clips directly onto the terminals of the 12V external battery.
Step 3: ApekSurv Configuration — Base Radio Settings
Turn on the base receiver and connect your field controller via Bluetooth. Fire up the ApekSurv application software, navigate directly to the main menu bar, and follow the configuration path: Device → Data Link. Set the primary Data Link type to External Radio.
To establish optimal data throughput, input the exact firmware settings required by the radio hardware into the ApekSurv software interface:
-
Radio Model Selection:
ABL90 -
Air Baud Rate (Over-the-Air link speed):
9600 -
Baud Rate (Serial hardware connection):
38400 -
Protocol Type:
TT450 - Channel / Frequency Selection: Select any clean, locally open operational channel (ensure you choose a frequency free from nearby regional industrial interferences).
-
Adaptive Function: Toggle to
ON.
Once you click apply and save the configuration profile, look directly at the physical indicator LED panel on the Harxon radio box—the transmission light should change to a steady, rhythmic blink, confirming active differential correction broadcasting.
Step 4: Rover Data Link Matching
Switch over your active ApekSurv Bluetooth link to pair with the mobile Rover receiver pole. Enter the software path: Device → Data Link. Change the data input selection type to Internal Radio.
To successfully receive the incoming correction stream, you must manually mirror the base configuration values on the rover:
- Set the Rover Protocol strictly to TT450 to match the Base.
- Tune the Rover to the exact identical Channel number / Frequency value assigned to the base station setup.
Step 5: Test and Verify Fixed Solution
Hold the rover pole steady in an open clearing. Monitor the top status header of your ApekSurv survey screen. Watch the positional solution cycle seamlessly from Single, through DGNSS, into Float, and finally lock securely onto FIXED.
Verify that your horizontal and vertical error bars fall within strict engineering tolerances. Field testing proves that with the Harxon ABL90 external radio running this exact optimization profile, the UHF data link maintains an effective, rock-solid transmission distance extending up to 15 km under open topographic conditions.
Troubleshooting: Common External Radio Failures
Symptom: The external radio is powered up and visibly transmitting, but the mobile rover remains stuck in Float or Single status indefinitely.
Cause: A deep configuration mismatch exists between the systems, typically involving a mismatched radio Channel selection or a Protocol variance.
Fix: Systematically cross-check both parameter profiles. Re-enter ApekSurv and verify that the Base and Rover are set to the identical Protocol (TT450), the identical Channel number, and the identical Air Baud Rate (9600).
Symptom: The Harxon radio panel indicators light up completely, but the unit fails to emit a regular transmit blink, and the rover receives no differential data.
Cause: The physical dedicated data cable is either plugged into the wrong receiver port, or the ApekSurv base data link software setting was incorrectly left on 'Internal Radio'.
Fix: Inspect the physical data line connection ends. Ensure the multi-pin cable is fully seated in the correct port. Open ApekSurv on the base controller, navigate to the Data Link submenu, and ensure that External Radio is actively chosen and saved.
Symptom: The data link drops out or drops down to Float status at a distance well below 5 km, far short of the rated 15 km threshold.
Cause: The transmitting antenna mast is tilted or poorly positioned, or dense physical structures/metallic obstructions are blocking the line-of-sight signal path.
Fix: Verify that the antenna support pole is perfectly vertical and plumb. For optimal coverage, always relocate the base station tripod setup to the highest open topographic vantage point available in the zone, well away from heavy metal machinery or dense structural walls.
Frequently Asked Questions
Which APEKS receivers support external radio connection?
Most advanced and professional-grade APEKS GNSS receivers equipped with an external multi-pin communications/serial port natively support external radio interfacing. Always check your specific hardware manual or product specification sheet to confirm external data link compatibility.
What is the maximum range of the Harxon ABL90 external radio?
When correctly integrated with an APEKS base station using high-gain antennas positioned with clear line-of-sight, the Harxon ABL90 external radio achieves a field-verified operational transmission range of up to 15 km.
Do I need a license to operate UHF radio in the field?
UHF radio licensing regulations vary significantly by country and jurisdiction. In many regions, operating high-power external radio transmitters requires a valid frequency allocation license issued by local telecommunications regulatory authorities. Always consult your regional guidelines before broadcasting.
Can I use a third-party external radio with APEKS receivers?
Yes. APEKS GNSS receivers utilize open industry-standard communication protocols. As long as the third-party external radio uses matching serial baud rates, pin-compatible data cables, and a shared open protocol (such as TT450), it can successfully transmit correction data from the receiver.
What happens if the 12V battery runs out during survey?
If the external 12V battery power drops below operational thresholds, the external radio will immediately shut down and stop broadcasting correction signals. The mobile rover will instantly lose its correction stream and drop from a Fixed solution to a Single/Uncorrected state. It is highly recommended to monitor battery voltage or carry a spare battery for full-day field operations.