Mrf101 40m pa usbpd

The Grenade 2026 - An MRF101 40m AM Linear Amplifier

USB-C Powered - 10W Carrier / 40W PEP - SMA Connectors

A bench-oriented 40-meter (7.0–7.3 MHz) AM linear amplifier built around a push-pull pair of NXP MRF101AN/MRF101BN LDMOS transistors — powered from a standard 100 W USB-C PD supply. Designed for experimental use under an FCC Part 5 license and general amateur use on 40m.

10 W carrier / 40 W PEP · 50 Ω in/out · runs from a laptop brick · absorptive harmonic termination

Features

• USB-C powered: negotiates 20 V / 5 A from any 100 W PD supply via a CH224K sink controller, then boosts to 48 V with an LM5122 synchronous boost converter.
• Dual power path: the boost output and a 48 V bench input are diode-ORed onto the main VDD rail — plug in whichever you have; both is fine.
• Absorptive harmonic termination: a high-pass diplexer branch dumps everything the output low-pass filter rejects into a 50 Ω / 6 W resistive load instead of reflecting it back into the PA drains. The transistors see a resistive load at all frequencies.
• Interlocked bring-up: the driver supply (LM2596HV buck) is enabled only after PD negotiation succeeds, or manually via a force-enable jumper (J5).
• Status LEDs: green = PD negotiated and boost alive; amber = main 48 V rail present.
• Temperature-tracked gate bias for the output pair.
• 7-element Chebyshev low-pass output filter, 7.5 MHz cutoff.

Repository layout

├── mrf101_40m_pa_usbpd.kicad_pro   # KiCad project
├── mrf101_40m_pa_usbpd.kicad_sch   # Schematic
├── mrf101_40m_pa_usbpd.kicad_pcb   # Board (220 × 130 mm, 2-layer)
├── BOM_mrf101_40m_pa_usbpd.csv     # Bill of materials (grouped, with quantities)
├── fab_usbpd/                      # Gerbers, drill files, paste layers
├── docs/
│   ├── USER_GUIDE.md               # Setup and operation
│   └── SERVICE_MANUAL.md           # Theory of operation, component reference, test points
├── CHANGELOG.md
├── LICENSE                         # CERN-OHL-S v2
└── README.md

Quick start

1. Bolt the board to a heatsink — the MRF101 pair requires one (TO-220 tab-down).
2. Connect a 50 Ω dummy load or antenna system to J2 (RF OUT). Never key without a load.
3. Power: plug a 100 W USB-C PD supply into J4, or 48 V bench into J3.
4. Green LED (D7) = PD negotiated; amber LED (D8) = 48 V rail up.
5. Apply drive (≈1 W nominal) to J1 (RF IN).

Full setup, bias adjustment, and first-power-up procedures are in docs/USER_GUIDE.md. Circuit theory, a complete component function reference, and oscilloscope test points are in docs/SERVICE_MANUAL.md.

Bill of materials

The complete grouped BOM is BOM_mrf101_40m_pa_usbpd.csv. Sourcing notes for the parts that matter:

Regenerating fabrication files

With KiCad 10.x:

KCLI=/Applications/KiCad/KiCad.app/Contents/MacOS/kicad-cli   # adjust for your OS

$KCLI pcb export gerbers mrf101_40m_pa_usbpd.kicad_pcb -o fab_usbpd/
$KCLI pcb export drill   mrf101_40m_pa_usbpd.kicad_pcb -o fab_usbpd/ \
      --excellon-units mm --excellon-separate-th

Include the paste layers (F.Paste/B.Paste) if you're having a stencil made.

Safety

This is a 40-watt RF power amplifier running on a 48-volt rail. Treat it accordingly: hot heatsinks, RF voltage on exposed copper, and enough stored energy in the bulk capacitors to be memorable. Operate into a proper load, within your license privileges, and keep fingers off the output network while transmitting.

License

This project is licensed under the CERN Open Hardware Licence Version 2 — Strongly Reciprocal (CERN-OHL-S v2). See LICENSE for the full text.

Copyright © 2026 Adam Blanquart

This source describes Open Hardware and is licensed under the CERN-OHL-S v2. You may redistribute and modify this source and make products using it under the terms of the CERN-OHL-S v2 (https://ohwr.org/cern_ohl_s_v2.txt).

This source is distributed WITHOUT ANY EXPRESS OR IMPLIED WARRANTY, INCLUDING OF MERCHANTABILITY, SATISFACTORY QUALITY AND FITNESS FOR A PARTICULAR PURPOSE. Please see the CERN-OHL-S v2 for applicable conditions.

Source location: https://github.com/ablanquart/thegrenade_2026/

As per CERN-OHL-S v2 section 4.1, any product you make from this design should carry a reference back to the source location above.