SM5BSZ has been writing and testing on this issue for a long time.
http://www.sm5bsz.com/dynrange/alc.htm
His various measurement on different HF transceivers makes for some
interesting reading. Just about every current radio model has this
problem with ALC induced splatter and ALC overshoot. Even radios like
the IC7800 seems to have this problem. It makes little sense having
transceivers with great third order IMD numbers when the ALC is reducing
the performance of the PA's high order IMD products to levels of a class
C PA at wider spacings. This problem is being made worst on the bands
by the large number of Tetrode amplifiers. It seems that just about
every one who runs a Emtron DX2 at reduced power seems to splatter,
however we all know its not the amp. When you trying to maintain a 400
watt legal limit output with a Japanese transceiver using low power,
the ALC becomes a monster on the loose certainly spiking and producing
grid current.
Numerous measurements here from SM5BSZ. The Ten Tec Orion as well as the
K2 also have this problem. The radio that seems to have a perfect ALC
on the measurements below seems to be the humble Kenwood TS50, its
higher order products seem impressively down at 20 khz.
http://www.sm5bsz.com/dynrange/rig_compare.htm
Craig
VK3HE
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