The spectrum of an IC-7000 keyed at full power on 14 MHz.
The serial number is 1008.
Note that the structures above 14.85 MHz are artifacts
due to inadequate calibration.
The time domain plot of the above spectrum,
an IC-7000 keyed at full power on 14 MHz.
It is obvious that there are sidebands due to instabilities
in the ALC loop.
The spectrum of the same IC-7000 keyed at full power on 144 MHz.
The gain of the transmitter is lower on 144 MHz compared to
14 MHz and the ALC does not have to act as much.
Therefore the keying clicks are lower on 144 compared to 14 MHz.
The spectrum of the same IC-7000 keyed at reduced power,
about 25 W, on 144 MHz.
When less power is desired, the ALC has to be more active.
The symmetric sidebands indicate AM modulation with an
overtone-rich signal of about 4 kHz.
When listening for weak signals 10 kHz away, the short pulses
of AM modulation sound as normal keying clicks - but very strong.
The time domain plot associated with the above figure.
IC-7000 at 12W on 144 MHz.
The oscillation is AM at a modulation level of about 4%
in amplitude (for sidebands about 35 dB below the carrier)
The modulation lasts about 2.5 milliseconds.
Instabilities in the ALC loops can generally be removed
by injecting a suitable DC voltage in the ALC input to
have the transmitter gain permanently set at a suitable
level where ALC action becomes very small or non-existent.