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MFJ-971 QRP PORTABLE ANTENNA TUNER
GENERAL DESCRIPTION: The MFJ-971 is a compact 200-Watt portable tuner
compatibly packaged with. MFJ QRP transceivers. The MFJ-971 is also a
perfect mate for any of today's ultra-compact SSB radios. It provides
a convenient cross-needle type SWR/Wattmeter and features a special
user-selectable 6-Watt range for QRP operation.
The T-match tuner covers 1.8-30 MHz and tunes almost any coax, wire, or
balanced-feed type antenna (a 4:1 toroid balun is built in for balanced
line).
READING THE CROSS NEEDLE SWR INDICATOR: The MFJ-971 uses a cross-
needle style meter to display FORWARD power, REFLECTED power, and SWR
simultaneously. To read Forward Power, observe the FORWARD meter
scale. To read Reflected Power, observe the REFLECTED meter scale.
To read SWR, observe where the two needles cross. The corresponding
red curve on the meter face displays your SWR reading. No "zero" or
"sensitivity" adjustment is required with cross-needle SWR displays.
POWER LEVELS: The FORWARD scale is calibrated from 0-300 Watts and
the REFLECTED scale from 0-60 Watts. In the high-power range, read
both scales directly (x 1). In the 30 Watt range, move the decimal
point one place to the left (x 0.1).
For QRP sensitivity (6-Watts FORWARD, 1.2-Watts REVERSE), you must
perform a simple conversion to obtain actual power. You can convert
in your head by moving the decimal point two places to the left and
doubling the reading (ie. 300 W = 3.00 x 2 = 6 W). You may also multiply
the scale reading times 0.02 on a pocket calculator -- or use this
conversion chart:
FORWARD SCALE
300W 30W QRP
REFLECTED SCALE
60W 6W QRP
----------------- ----------------
300W 30W 6W 60w 6w 1.2W
250W 25W 5W 50W 5W 1.0W
200W 20W 4W 40W 4W 0.8W
150W 15W 3W
3
0
w
3W 0.6W
100W 10W 2W 20W 2W 0.4W
50W 5W 1W 10W 1W 0.2W
SELECTING POWER RANGE: The "IN" position of the meter's range
switch selects the 30-W range. The "OUT" position provides a choice
of 300-W or 6-W QRP range, as determined by two jumpers on the
powermeter pc board (see Figure 1A,1B). When jumper plugs are
installed in position "A", meter sensitivity is 6-Watts (QRP). When
installed in position "B", sensitivity is 300-Watts. Jumpers are
normally set for "B" (High Power) at the factory.
CAUTION: Running high power while in the "QRP" range could damage your
meter movement.
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