MFJ-941EK Tuner Kit Instruction Manual
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OPERATING INSTRUCTIONS
[ ] Logging regularly used tuner settings is useful for two reasons. First, it speeds
your setup time considerably. Second, it will alert you right away if something has
changed out at the antenna site.
Note that T-networks are designed to match a wide range of loads, but they are
not designed to suppress your transmitter's harmonic content. The T
configuration is basically a high-pass filter, so it's up to your transmitter to do the
filtering and meet FCC requirements for harmonic suppression.
4. Using the 4:1 Balun:
The 4:1 balun transforms loads connected at the Balanced Line terminal posts
from Zin to Zout/4 and converts the signal path from balanced to unbalanced.
Thus, a 200-Ohm load will be transformed to 50 Ohms (SWR = 1:1) and a 400-
Ohm load will become 100 Ohms (SWR = 2:1).
BALANCED LINE
WIRE
GND
Install
Jumper
By switching in the T-network, it's possible to correct most (but not all)
mismatches you might encounter. Some antenna and transmission line
mismatches are so extreme that they defy correction. Low-impedance excursions
are especially problematic for the tuner's balun because the 4:1 step-down
transition will drive the impedance even lower -- sometimes beyond the range of
the T-network! Fortunately, there are "fixes" for many of these problematic
configurations.
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