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multi_assy_053019.pdf
Schematic:
Tuner usage
The tuner is rated at 5W CW, 10 watts PEP max. and incorporates the N7VE LED absorption bridge
circuit for sensing SWR. In the TUNE position, you cannot damage your transmitter caused by a high
SWR. The worst your transmitter is looking at is a maximum of 2:1 SWR in the TUNE position. The
LED is only showing reflected power. At full brilliance your SWR is 4:1 or greater, at half brilliance your
SWR is approximately 2:1, and the LED will completely extinguish at 1:1.
Tip from Dan…If your led
does not completely go out at 1:1 there may be a little too much gain on L1, the indicator transformer.
Just reduce the turns on the high side of the tap, one or two turns.
Adjusting for a wire antenna match
With your transmitter and antenna connected to the tuner, set the tune/operate to the tune position. Set
the adjustment knobs to the center position. Note: Tune mode, maximum power Input – 5 Watts.
Place the HI/Low impedance switch in the Hi position. The Hi impedance setting provides the most
efficient coupling and operation. Briefly key your transmitter and attempt to adjust the knobs to dim the
LED. Continue adjusting back and forth until the LED is out or is as dim as possible. If the adjustments
do not produce adequate dimming of the LED switch to the Low impedance position and repeat the
adjustment process. Note: Under some conditions of match adjustment the LED will not go completely
out. Your antenna will be tuned for proper operation even if the LED does not dim completely out.
Switch the tune/operate switch to the operate position.
Use all the normal cautions throwing wires up in the air near power lines.
Additionally, after the antenna is tuned up, keeping the bridge in the circuit (Tune position) will reduce
the power by a factor of four to a matched antenna. This can occasionally be useful when trying to bring
a 3w QRP transmitter to under the 1w level for certain sub-one watt contest multipliers.
Notes:
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