Topband: preamps homemade ...

[K9AY]

> The Anzac AM(C)-132 and AM(C)-134 amplifiers have 3OI of +49 dBm with a
> power
> dissipation of 2.6W.
>
> Rick N6RK


With a dissipation of just 2.6W, I suspect that these units either (a) have
feed-forward or other linearization schemes, or (b) are spec'd for Output
Intercept Point (OIP3), which must be reduced by the gain of the amplifier
to get Input Intercept (IIP3), a more meaningful specification.

The amateur literature uses IIP3 almost exclusively, since it represents
signal levels arriving from the antenna -- a realistic situation.
Manufacturers of devices and amplifiers tend to use OIP3 because it's a
bigger number and looks better in an ad or on a spec sheet.

For reference, a 'classic' 2N5109 or 2N3866 feedback amp with 13 dB gain,
consuming <1 watt can have an IIP3 around +25 dBm and an OIP3 of +38 dBm.

73, Gary
K9AY