The following images depict the results of a two tone test I ran on
the repaired FT-991. The rear data port was used to inject the signal
from a PC running
SpectrumLab. Tones where set to 1000Hz and 1575Hz respectively. The RF out of the Yaesu FT-991 was fed into the SM-220.
This image shows the transmitter flat topping, settings where 100W
and ALC increased slightly to peak RF output (a few bars visible). The
maximum output power achieved and observed on the external power meter
was 90W (10% accuracy at full scale). Flat topping is a symptom of the
PA being over-driven.
With reduced ALC, i.e. no visible ALC indication in fact one step
(click) below zero observable ALC and with the FT-991 set to 100W, the
following output was observed.
