The 986 is a differential T tuner. If this your first, do not buy. It is fussier to tune. The 986 is a 3kw input, which makes a 1500 watt tuner.The 989 used to be called a 3kw tuner, but now is rated by actual output from the amp.
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Quoted from the 986's manual
" Understanding Power Ratings
There are no standardized power rating systems for tuners. The names used (i.e. 3 kW Tuner) carry over
from the time when amplifiers were rated by peak power input, and not the true RF power output. For
example, the one thousand watt Johnson Matchbox was rated to handle a 1000 watt plate modulated AM
transmitter (four kilowatts PEP transmitter input and 3000 watts PEP RF output). The Heathkit SB-220
was called a two kilowatt amplifier, and the rated CW output was approximately 600 watts. Matching
tuners were called 2 kilowatt tuners, and these tuners safely handled 600 watts of CW power and 1200
watts PEP SSB.
The FCC has changed the power rating system of amplifiers, and tuners no longer follow amplifier
power ratings. Most typical 1500 watt tuners remain able to safely handle 400-600 watts CW, and 600-
900 watts PEP SSB.
Load conditions and control settings also greatly affect the power handling capability of the tuner. Tnetworks
typically handle more power on higher frequency bands into higher load impedances. The
worst operating condition for T-network tuners are low impedance capacitive reactance loads. Tnetwork
tuners always handle the least power when operated on 160 meters into low impedance
capacitive reactive loads.
Follow the guidelines in this manual to avoid exceeding the ratings of this tuner."