5. Measurement of radiant power (RAD)
In matching the impedance or monitoring the operat-
ing conditions of transmitter, both the forward power
(Pf) and the refrection power (Pr! should be observed.
If the refrection power (Pr) is extremely large (SWR
of load is unusually high) while observing "Pt" alone,
a large "Pf" is measured on the meter even when
little power is consumed in the load. On the other
hand, if only the "Pr" is observed, the meter in-
dicates a smaller refrection power (Pr) when the
output of transmitter is decreased due to some con-
dition of the load .t>eingused, creating an illusion that
the refrection power was very small. However, this
can be eliminated by setting the function switch to
..'
2.5
a:
;< 2
(f)
0.05
0.15 0.2
Pr/PI
0.25
0.3
O. I
Fig. 7
the RAD position with PF-810 connected near to the
load. In this way, the power (Pf-Pr) consumed in the
load is indicated on the meter, which not only offers
a convenience to impedance matching work but also
allows you to monitor both the forward power and
refrection power at the same time because the power
measured is decreased as the refrection increases. Ac-
cordingly, when PF-810 is used as a monitor, the
function switch is normally set to the RAD position.
Even when PF-810 is connected near to the trans-
mitter, the power measured on the meter can be
regarded as a radiant power as long as the return loss
of the transmitting system is disregarded. When the
meter indicates a maximum radiant power (RAD), it
means that the transmitter or the antenna coupler is
properly adjusted.
6. Antenna selector
The antenna selector permits selection of antennas or
dummy load. Two different antennas, such as 3.5/7-
MHz 2-band dipole antenna and 14/21/28MHz 3-band
Vagi antenna or HF band and 144MHz band antennas,
can be connected to ANT1 and ANT2, respectively.
A dummy load can also be connected to either ANT1
or ANT2, instead of connecting an antenna, for
tuning or testing the transmitter.
By pressing the antenna selector pushbutton, ANT1
is connected to the instrument. By pressing the
button once again, it is releaspd and ANT2 is con-
nected. Note that the power of the transmitter should
be turned off whenever the button is to be pressed.
11
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