HARVARD H407, Руководство пользователя

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SWR Power Losses
1:1 = 0%
1.3:1 = 2%
1.5:1 = 3%
1.7:1 = 6%
2:1 = 11%
3:1 = 25%
4:1 = 38%
5:1 = 48%
6:1 = 55%
10:1 = 70%
TUNING YOUR ANTENNA
For optimum performance, an SWR meter should be used to tune the antenna. However,
since these meters can be EXPENSIVE, not everyone may want to invest in a purchase.
If possible, borrow one, If you are unable to borrow one, the RF output meter on your
transceiver can be used as a GUIDE to antenna tuning. While it Is not 100% accurate, it
is generally better than no tuning at all. Always tune your antenna in an open area. Wires,
metal and copper tubing if nearby can effect the tuning. Never tune an antenna inside a
garage, under a metal car port, next to a metal truck, etc.
A. USING YOUR TRANSCEIVER OUTPUT METER AS A TUNING GUIDE
After installing your antenna system, place the whip halfway into its receptacle and turn
your transceiver to Channel 20. Depress the switch on your transceiver microphone, and
make note of the reading on your RF output meter. Loosen the adjustable whip section and
move it 1/8 to 1/4 inch down. Again depress the transmit switch, if the reading is the same
or lower continue moving the whip down 1/4 inch at a time until the LOWEST reading is
obtained on your transceiver RF meter. If the reading was higher, move the whip up 1/4 to
1/2 inch the first time and 1/8 to 1/4 inch thereafter until the LOWEST reading is obtained
on the RF meter. That's right THE LOWEST READING. Your RF output mater is a voltage
sensing device. It is installed in the RF output circuit and senses the voltage near the
antenna terminal. In a perfectly tuned system all of the voltage is transferred from the
output transistor and passed to the antenna. As an example, let's use the figure 10. If
there Is SWR on the line, the forward voltage is 10 and a reverse voltage appears (let's
say it's 2). The meter circuit now sees 20 and shows a higher reading. You can see that
because of the way most RF output meters work, the LOWER your RF output meter reads
the better your antenna is tuned. Of course, if th e meter reads less than 1/2 scale, it may
indicate a problem in your set and should be checked. Similarly, an extremely high reading
may indicate a problem in your antenna.
An RF output meter can tell you much....especially if you know how to use it.