Input/output connections.

DL4MEA shows using "flying" ut141 semi rigid leads with sma connectors for the input and output connectors, but i decided that they were too delicate for contest abuse. I decided to mount four hole chassis mounting sma connectors, with long ptfe insulation on the heatsink side of the amplifier. The problem with this is that the heatsink fins get in the way. Using a dremmel drill the fins were removed leaving a flat mounting surface around the connector. 3 M2.5 holes were drilled and tapped for the output connector as there was only room for 3 (see below) and four  M2.5 holes tapped for the input connector.

Component modifications.

All the DL4MEA component changes and moves were done as described, however originally on the web site DL4MEA called for the output copper foil to be 20x15mm, which is impossible to fit in the space available, a piece 20x10mm was successfully used. Make sure the right hand edge does not get too near the chassis or it will arc and disintegrate! Capton foil was used to unsulate the ground connections under the copper foil

Output indicator

Although the original amp has forward and reverse power detectors, they are not in circuit with the current configuration. However there is a coupler just before the output connector. The track was cut between the two ceramic chips and a hot carrier diode soldered in the gap. The detector output is brought out on the heatsink side of the amplifier through the existing hole.

Bias

Although the DL4MEA pages show a variable regulator for the bias supply, information from Dave Powis G4HUP revealed that the optimum voltage was 5V so a 7805 could be used. This was mounted in the position shown by DL4MEA. It was found that if no bias was applied to the bias pin no current was taken from the 28V supply. So a 24V relay was used to switch the 28V to the input of the regulator on transmit, saving unnecessary heating.