The Service Menu isn’t a set of regular user options (like RF gain or mic gain). Instead, it’s a protected diagnostic area used at the factory to calibrate:
Accessing it voids the warranty if misused—but for experienced operators, it’s a precision instrument.
If you own an AnyTone AT-5555N II, you already know it’s one of the most feature-packed 10-meter/12-meter radios on the market. But did you know there’s a hidden "Service Menu" that lets you fine-tune everything from transmit power to meter calibration?
Warning: This is not for the faint of heart. Changing these settings can void your warranty, brick your radio, or make it illegal to transmit. Proceed at your own risk.
⚠️ Warning: Incorrect adjustments can degrade performance, cause spurious emissions, or even damage the final transistors. Document original settings before changing anything.
Here’s the key sequence (confirmed across multiple firmware versions): anytone at-5555n ii service menu
The screen will now show “SERVICE” or a calibration parameter (e.g., rEF or PLL). Use the CH/UP/DN knob or channel selector to scroll through parameters.
Here is a list of the most common parameters you will find in the AT-5555N II service menu. Note: Nomenclature varies slightly between firmware versions 1.0, 1.1, and 2.0.
| Parameter Code | What It Does | Typical Adjustment Range | Technician Notes | | :--- | :--- | :--- | :--- | | POWER HI | Sets RF output power on High setting (AM/FM). | 0 - 255 (Digital to Analog Convertor value) | Do not exceed 20-25W AM carrier. Set for ~20W carrier / 80W PEP. | | POWER LO | Sets RF output power on Low setting. | 0 - 255 | Usually set for 1W to 5W for driving amplifiers. | | F-ERR (Freq Error) | Synthesizer frequency trimming (PLL reference crystal). | -300 to +300 Hz increments | This requires a frequency counter. Tune to CH20 (27.205 MHz). Set to 0 Hz offset. | | SSB BIAS | Adjusts idle current for SSB linearity. | 0 - 255 | DANGER: High voltage inside. Do not touch. Set for ~100mA idle rise. | | AM CARRIER | Adjusts the AM carrier level relative to PEP. | 0 - 255 | Standard spec: Carrier is 1/4 of PEP (~25W carrier for 100W PEP is wrong). | | MOD AM | AM Modulation depth limiter. | 0 - 255 | Increase to ~95-98% using a scope. Do not go beyond 100% (flat-topping). | | MOD FM | FM Deviation level. | 0 - 255 | Standard is ±5 kHz deviation. | | S-METER 9 | Calibrates S9 signal level (usually -73 dBm). | 0 - 255 | Requires a signal generator. | | S-METER 1 | Calibrates S1 signal level (usually -121 dBm). | 0 - 255 | Requires a signal generator. | | SQ OPEN | Squelch threshold open point. | 0 - 255 | Sets when squelch opens with no signal. | | MIC GAIN | Global microphone preamp gain. | 0 - 255 | Be careful; too high causes distortion. |
Tom needed to tweak his Anytone AT-5555N II handheld for better performance on a local repeater. He wasn’t a radio tech, but he wanted a safe, reversible change — nothing that would void warranty or break the radio.
Entering service menu (safe approach)
What Tom checked (and what he avoided)
Making a safe change
Testing and rollback
Final notes and best practices
If you want, I can:
⚠️ Disclaimer: The service menu contains critical calibration data. Incorrect settings can render the radio inoperable, cause it to transmit on illegal frequencies, or violate FCC/Ofcom regulations. Proceed at your own risk.
Proceed at your own risk. Entering the service menu and changing values incorrectly can:
Recommendation: Write down the original value of every setting you change. Do not adjust anything unless you own a calibrated frequency counter, a watt meter with a dummy load, and an oscilloscope (for modulation).
Do not trust online "mod" videos blindly.
Many YouTube influencers will tell you to max out every value (PWR HI = 255, MOD AM = 255). This is reckless. The digital settings correspond to analog voltages. Setting "255" on a parameter that expects a sine wave output will result in a square wave—burning your finals instantly. The Service Menu isn’t a set of regular
Furthermore, the Service Menu does not lock out illegal frequencies. While the AT-5555N II is primarily a 10m/12m radio, misuse in CB bands (27 MHz) with excessive power is illegal and disrespectful to other band users.
The Service Menu contains parameters essential for the functionality of the Phase Locked Loop (PLL) and the RF Power Amplifier. The exact numbering may vary by firmware version, but the functions remain consistent.