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[Amps] ALC Overshoot

Subject: [Amps] ALC Overshoot
From: zdtech <>
Date: Sat, 10 Jun 2006 10:25:59 +1000
List-post: <>
SM5BSZ has been writing and testing on this issue for a long time.

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.

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