ICOM IC-910H Power Mod

For usage with QO-100 UpConverter by AMSAT-DL output power should not exceed ~ 2.5W (taking cable loss etc. into account). Therefore PA gain for 430MHz band has been reduced by adjusting R3 for “Total gain adjustment for 430M” according to service manual.

Excepert from IC-910H service manual

Original trimmer value was set like this:

R3 trimmer in original state

The trimmer was adjusted so that the total output power is now ~ 2.5W out (FM carrier) when RF PWR trimmer is set to maximum power.

Measured output power after trimmer adjustment

At the same time output power of 144MHz Band was reduced to minimum (using R503) as the 144MHz band is used for reception with AMSAT-DL DownConverter. In order to prevent the unit from being killed by RF the 144MHz band PA gain was reduced to minimum resulting in ~500mW output power with RF PWR trimmer set to max at the front panel.

Original trimmer setting for “Total gain adjustment for 144M” was like this:

Orignial state of trimmer R503

23cm unit settings have not been changed.