Vertex VX-5500L 6 Meter Band Modification (50–54 MHz)

The Vertex Standard VX-5500L is a rugged, high-performance low-band mobile transceiver widely used in commercial, government, and public safety communication systems. Known for its durability and strong RF performance, it offers excellent receiver sensitivity, reliable output power, and flexible programming through its firmware (.C49 file).

These radios were produced in two main versions:

1. Version A: 29.7 – 37.0 MHz
2. Version B: 37.0 – 50.0 MHz

Both models are capable of delivering 70 watts on high power.

In this project, we’ll focus on Version B, originally covering 37–50 MHz. The goal is to extend its frequency range up to 54 MHz, enabling full 6-meter amateur radio (50–54 MHz) operation.

The modification process includes two parts:

1. Firmware Modification: Adjusting the master frequency parameters (3110 and 7110 lines) within the .C49 file to reprogram the internal reference and frequency limits.

1. Hardware Modification: Making small changes to the VCO (Voltage Controlled Oscillator) circuit and RF front-end filters to ensure proper oscillation and stable transmit/receive operation up to 54 MHz

1. Vertex VX-5500L low-band version B

2. Programming cable (CT-105 or compatible), Computer with USB adapter FIF12

3. Programming software supplied. Download

4.54MHz.c49 file edited for 54MHz 6m Ham Band Download

5. Soldering tools (if any hardware mod needed), remove the VCO screen

Before performing any modifications, it’s important to read and back up the original configuration (.C49 file) from your radio. This ensures you can always restore it if something goes wrong.

Vertex FIF-12 programming adapter and CT-105 programming cable (connects between the adapter and the radio) Diver Download

CE49 programming software (Vertex Standard software for VX-5500 series) Download

A Windows PC, win10 ok

Connect the FIF-12 adapter to your computer and attach the CT-105 cable between the adapter and the VX-5500L radio.

Connect the hardware:

1. Plug the FIF-12 adapter into your PC.
2. Attach the CT-105 cable between the adapter and the VX-5500L radio.

Enter PC Clone Mode:

1. Turn the radio OFF.
2. Then press and hold the [POWER] button and the bottom (LOWER) button together.
3. Keep both buttons pressed until the display shows “PC CLONE” message.
4. The radio is now ready to communicate with your PC.

Launch the CE49 software on your computer.

In the Configuration menu, select the correct COM port (for example COM2, COM3, etc.).

Click "UPLOAD" “Read from Radio” — the CE49 software will read the full configuration from the VX-5500L.

Save this original .C49 file as your backup copy (for example, VX5500L_original.c49).

Once the backup is saved, upload the modified .C49 file (from my provided link) into the CE49 software.

Click "Download" “Send to Radio” to write the new configuration to the VX-5500L.

After backing up your original configuration, the next step is to edit the firmware (.C49 file) so the radio can operate up to 54 MHz. The changes involve adjusting the internal master frequency reference lines used by the VX-5500L’s microprocessor.

Hex Editing the .C49 File for 54 MHz Upper Limit

This step explains how to manually modify the .C49 configuration file using a hex editor to extend the upper frequency limit of the VX-5500L from 50.000000 MHz to 54.000000 MHz.

The .C49 file stores various parameters that define the radio’s transmit and receive ranges. By adjusting these values directly in hex format, you can unlock additional frequencies for amateur use.

Tools You’ll Need

1. A Hex Editor (for example, HxD, Hex Workshop, or similar)
2. Your original .C49 file (backed up in Step 1)
3. The CE49 programming software to re-load the edited file into the radio

Understanding the Data Format

Inside the .C49 file, the band limit values are stored as 32-bit integers representing frequency in Hz (e.g., 50,000,000).

However, the data is stored in Big Endian (Motorola) byte order — not the usual Intel (Little Endian) format that Windows uses.

This means that:

1. Decimal 50,000,000 = Hex 02FAF080 (in Motorola / Big Endian)
2. But the same value in Intel / Little Endian would appear as 80 F0 FA 02

If you search for 02 FA F0 80 in your .C49 file using a hex editor, you’ll find the upper frequency limit for the VX-5500L (50.000000 MHz).

Technical Analysis

When analyzing .C49 files from the CE49 software, I discovered that:

1. The microprocessor used in the VX-5500 series is based on the Intel 8051, which internally stores multi-byte values in Big Endian order.
2. This is why searching for 02FAF080 (Intel-style) fails — you must search for 02 FA F0 80 instead.
3. The CE49 software creates .C49 files with both Master (3110) and Slave (7110) configurations, each with their own frequency range parameters.

1. 3110 = Master frequency range
2. 7110 = Slave frequency range

Since a modified .C49 file for the VX-5500L B has already been provided, you do not need to manually edit the firmware yourself.

1. Simply follow Step 1 to upload the provided .C49 file to your radio.
2. Then proceed to Step 4 for any necessary hardware modifications
3. If you want to understand the detailed configuration changes, you can read the full explanation in the original Step 2 section, but it is optional.

This step ensures beginners can safely complete the modification without touching the hex file, reducing the risk of errors.

To ensure the VX-5500L operates reliably up to 54 MHz, small hardware adjustments are needed in the VCO and RF sections. This step involves unsoldering the VCO shield, retuning coils, and adjusting the PA and HF components.

1. Remove the VCO Shield

1. Carefully unsolder the VCO shield without damaging adjacent components.
2. Holding the radio in a rubber-padded vise with tilt helps access the solder points.
3. After modification, resolder the shield with moderate heat; less is needed than removal, especially when using 60/40 solder.

2. Identify VCO Sections

1. The receiver VCO has two sections:
2. 37.0–43.49 MHz → lower section T1011 (no adjustment needed)
3. 43.50–50.0 MHz → upper section T1005 (adjust for 50–54 MHz operation)
4. Only the upper section needs retuning for 6-meter coverage.

3. Adjust the Receiver VCO

1. Put the radio in receive mode at 54.00 MHz.
2. Measure VCO voltage at TP1010 again.
3. Adjust T1005 until the voltage reads 7.0 ± 0.1 V.
4. Do not touch T1011; it is for receiving 43.49 MHz and below.

4. Adjust the Transmitter VCO

1. Program the radio to 54.00 MHz.
2. Key the transmitter.
3. Measure VCO voltage at TP1010.
4. Adjust T1006 until the voltage reads 7.0 ± 0.1 V.

5. Adjust the Synthesizer Master Reference Oscillator

1. The transmit frequency is set by variable capacitor TC1001.
2. Ensure the radio is at normal operating temperature.
3. Adjust TC1001 so the transmit frequency is within ± 100 Hz of the programmed frequency (54.00 MHz).

Notes

1. Always verify the frequency with a frequency counter after adjustments.
2. Minor PA and Harmonic Filter (HF) coil adjustments may be needed to maintain proper output and clean signal.

For comprehensive technical details, alignment procedures, and component locations, refer to the official service manual for the Vertex Standard VX-5500L. This manual is an invaluable resource for anyone undertaking hardware modifications or seeking to understand the internal workings of the radio.