RM Italy KL503HD 300W Linear Amplifier with Receive Preamp
The RM Italy KL503HD is a 300W maximum-output linear amplifier with a six-position rotary power control and a switchable receive preamplifier. It accepts 1–35W input across its supported modes.
Key features
- Maximum output: Manufacturer-rated 300W.
- Input range: 1–35W across supported AM, FM, SSB and CW modes.
- Output control: Six-position rotary selector.
- Receive preamplifier: Switchable from the front panel.
- DC supply: 13.8V nominal with a 40A supply rating.
- Cooling: Heatsink housing with space required for ventilation.
- Size and weight: Approximately 11.81 inches long × 7.48 inches wide × 2.64 inches high; approximately 4.52 lb.
Specifications
| Specification | Manufacturer rating |
|---|---|
| Model | RM Italy KL503HD |
| Frequency range | 25–30 MHz |
| Modes | AM, FM, SSB and CW |
| Maximum output | 300W |
| Input power | 1–35W, all modes |
| Supply voltage | 13.8V DC ±1V |
| Power-supply rating | 40A |
| Maximum current draw | 30A |
| Output control | Six-position rotary |
| Receive preamplifier | Switchable |
| Input VSWR | 1.1–1.5:1 |
| Fuses | Three 10A fast-blow fuses |
| Dimensions | Approximately 11.81 inches long × 7.48 inches wide × 2.64 inches high |
| Unit weight | Approximately 4.52 lb |
Setup requirements
Check the driving radio's RF output before switching on the amplifier. Never exceed the 35W input limit, and do not use the amplifier's output selector as a substitute for reducing excessive drive at the radio.
Use a suitable DC supply and correctly rated wiring. Allow clear airflow around the heatsink, and connect a properly matched antenna system or suitable dummy load before transmitting. The antenna, coax and test equipment must be suitable for the operating power and frequency.
The manufacturer specifies a maximum bypass power of 50W with the amplifier switched off. Avoid prolonged high-duty-cycle transmission and allow the heatsink to cool as needed.
US operating restriction
External RF power amplifiers must not be used to increase the transmitting power of a US CB Radio Service station. This amplifier is not a legal CB power upgrade. Observe all applicable equipment-authorization and operating requirements.
Frequently asked questions
Is the KL503HD a radio?
No. The KL503HD is an external linear RF amplifier that works with a separate transceiver. It is not a standalone radio.
How much input power can the KL503HD accept?
RM Italy specifies 1–35W input in all supported modes. Do not exceed 35W. Reduce the driving radio's output rather than relying on the amplifier's power selector to make excessive input safe.
What output power does RM Italy specify?
The manufacturer specifies 300W maximum output. This is the amplifier's maximum rating, not its required operating level.
What power supply is required?
Use a 13.8V DC supply rated for at least 40A. RM Italy lists maximum amplifier current draw of 30A; supply capacity and maximum amplifier draw are separate specifications.
Does it have adjustable output power?
Yes. The KL503HD has a six-position rotary output selector on the front panel.
Does it have a receive preamplifier?
Yes. A front-panel control switches the receive preamplifier on or off.
How large is the KL503HD?
Converted from the manufacturer's specifications, the unit is approximately 11.81 inches long × 7.48 inches wide × 2.64 inches high and weighs approximately 4.52 lb.
Can I use it to increase CB transmitting power in the United States?
No. US CB Radio Service rules prohibit using an external RF power amplifier to increase a CB station’s transmitting power.
*These units are for industrial, scientific, medical, or export use only. It is a violation of US FCC regulations to operate these units on the Citizens Band or Amateur Radio Services in the United States. Please check regulations in your country before operating these unit.