33cm amplifier

The TPL PA8-1AA-M is a 806-870MHz FM amplifier that's showing up on the used market for cheap. I'd like to convert it for use on the 33cm ham band and also for linear / non-FM usage.

oops I voided the warranty

As designed the PA8-1AA-M has a Motorola MHW2821-1 amplifier module. This -1 part is specified for 806-870MHz usage. The MH2821-2 looks to be a drop-in replacement for 890-950MHz.

Replace the device, maybe tweak the input and output coils for max power and that might be it ... for FM.

I'd like to use this on SSB, so this needs to be linear. Many other of these FET-type amplifier modules are specified for FM but can be used for SSB by adjusting the device bias. Devices such as the Mitsubishi M67760HC mention this along with the RA20H8994M. Unfortunately those two devices are a little big to fit in the space occupied by the MHW2821.

unmodified unit

So I'm probably going to see if the bias on the MHW2821 can be adjusted to allow for use on SSB and if not, is there any reasonable way to substitute a different device.

As of this moment, all schematics and the service manual is available on the FCC OET website when searching for the FCC ID.

At the moment, this is the start of a work in progress.

This page last modified Mon Sep 7 17:37:16 CDT 2020 by timc!