MFJ MFJ-925, Instruction Manual

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MFJ-925 Super-Compact IntelliTuner Automatic Antenna Tuner Instruction Manual
©
2006 MFJ Enterprises, Inc.
11
Miscellaneous
Antenna Memory
The “memory resolution” is the width of frequency spectrum that the tuner recognizes as being the same
as a tuned frequency already in memory. The memory resolution is approximately 0.1 percent of the
lower frequency of each amateur band. For example, the memory resolution on the 40-meter band (7000
to 7300 kHz) is 7 kHz; if the tuner has memorized a setting for 7050 kHz, it will automatically call up this
setting for any frequency from 7047 to 7053 kHz. Memory resolution is smaller at lower frequency to
accommodate the higher antenna Q and larger at higher frequency where the antenna Q is lower. The
memory resolutions for the HF amateur bands 160 through 10 meters are:
Meter Frequency Range (kHz) Memory Resolution (kHz)
160 1800 – 2000 2
75/80 3500 – 4000 4
60 5330.5, 5346.5, 5366.5, 5371.5 and 5403.5 5 memory locations
40 7000 – 7300 7
30 10100 – 10150 10
20 14000 – 14350 14
17 18068 – 18168 18
15 21000 – 21450 21
12 24890 – 24990 25
10 28000 – 29700 28
Table 2. Memory Resolution.
The memory resolution for non-amateur frequency bands between 160 and 10 meters is approximately
0.2 percent of the lower frequency of each band. There are two primary memory banks, each with four
secondary memory banks. Each secondary memory bank has 2500 memory locations. Tuner settings are
stored in memory separately in primary memory 1 and primary memory 2. This provides memory for up
to eight different antennas. See “ALT Button” on page 5. Defaults are memory banks 1A and 2A ON.
IntelliTune
TM
Algorithm
When
the tuner cannot find an appropriate setting in its memory, it begins its calculation function. It
measures the complex impedance of the antenna (load) at the transmitting frequency, then it calculates the
LC components needed for a match. Then it fine-tunes the components for minimum SWR. If for any
reason the tuner cannot calculate the load impedance, it proceeds to yet another method of calculation.
LC Limits
The upper limits of inductance (L) and capacitance (C) are factory-limited according to frequency and
maximum power rating; i.e., higher frequencies need less inductance and less capacitance when the L-
network is properly tuned. These limits are built into the MFJ-925 to prevent matching of extreme load
impedance outside the tuner’s specification, which may result in excess voltage and/or current across the
tuner’s components.