Output Attenuator

Introduction

It is possible to add a programmable output level attenuator to the Portsdown transmitter. As of software version 201801061, the output attenuator can be used to adjust the output level of the Portsdown Signal Generator. It is planned that a future software version will allow programmable output levels to be set for each band (and possibly for additional transverter outputs).

Attenuator Types

Attenuators based on the PE4302, PE4312, HMC1119 PE43703 or PE43713 are supported. The PE4302 and PE43703 types are readily available on eBay for under £20. The preferred type is the PE43703 illustrated here:

Data sheets are available at these links: http://www.psemi.com/pdf/datasheets/pe4302ds.pdf http://www.psemi.com/pdf/datasheets/pe43703ds.pdf http://www.analog.com/media/en/technical-documentation/data-sheets/HMC1119.pdf.

Preparation

As supplied, the eBay pre-built attenuator boards are generally configured for control by DIP switches, not by a Raspberry Pi. NOTE THAT IF CONNECTED WITHOUT MODIFICATION THEY MAY KILL YOUR RASPBERRY PI! The modification details for the PE43703 are details here. Please could a PE4302 owner publish similar information??

There are 3 signal lines used to program the PE43703: LE (Latch Enable), CLK (Clock) and Data. For DIP switch programming the LE line is connected to +5v. This line needs to be disconnected from +5v and connected to the external programming pin. Referring to the picture below (pre-modification)