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LPU Prototype

Linear Power Unit (LPU) - HPSDR Simple Power Supply

Project Leader: Scotty WA2DFI

"LPU" is the project-name for a simple HPSDR power supply. Although power supplies are widely available, the LPU will provide a convenient low-noise solution until the more complex Demeter power supply is completed. The LPU (as well as Demeter) are specifically designed for the HPSDR project. With the approaching release of Mercury, this is the last hardware part of a basic functional HPSDR transceiver.

The LPU will not take the place of Demeter; it is intended as an interim solution to power HPSDR boards until Demeter is completed.

Further information will be presented on this page as it becomes available.

73, Scotty WA2DFI

Updated: (26th December 2008):

All 5 LPU prototypes assembled and tested. Added pictures. Updated schematic to XA4, which matches the prototype PCBs. Except for the capacitors in parallel with C3 and C7, it is accurate for a functional unit.

LPU Bottom View
LPU in Atlas backplane with Mercury and Ozy

Updated: (18th December 2008):

First LPU PCB assembled. +5V and +3.3V regulator outputs oscillate. Added additional capacitance to each output by adding 47uF 10V tantalum capacitors in parallel with C3 and C7. Outputs now stable.

Updated: (17th December 2008):

Received prototype PCBs. Parts previously ordered and all in stock. Many thanks to Lyle, KK7P for doing the PCB layout and edits.

Updated: (30th October 2008):

1 Physical

The LPU (Linear Power Unit) is a self-contained power supply board for HPSDR. It is mounted onto a 20-pin ATX connector that mates with the connector on the Atlas board.

2 Requirements

HPSDR boards require power outlined in the following table.


3 Electrical

The LPU accepts a 12VDC regulated input and produced the following outputs:


The LPU does not produce -5V or any standby voltages. It ignores the ATX power-on signal and is always on. There is a jumper to shut off the -12V switching regulator when it is not needed in order to eliminate RF noise.

4 LPU Feature List

Input power: 12.5V – 14.5V regulated DC input

Outputs: +12V@2A, +5V@2A, +3.3V@2A (opt), -12V@100mA

Poly fuse on each regulator input: +12, +5, +3.3V (opt), -12V regulators

Plugs into Atlas backplane ATX connector

Mounting holes allow direct mounting to Atlas backplane

Strap disable for -12V to reduce noise

Dual power-pole input connector

Internal dual power-pole output connector for PA or accessories

Estimated PCB size: (LxWxH): 119mm X 44mm X 40mm

Estimated overall size: (LxWxH): 137mm X 54mmX 60mm

Schematic: Media:LPU_XA4.pdf