RF Directional Thruline® Wattmeter Model APM–16
4
vs.
The simple relationships:
can be used to convert between the standing wave ratio (
and the reflected/
forward power ratio
, which can be directly read from the Thruline
Wattmeter. The relationship between
and
is graphed in
Figure
3
and
Figure
4
.
Note:
Attenuation, measured in dB, can be derived from the
power ratio by the equation
N
db
= 10 log
.
VSWR scales and their attendant controls for setting the reference point have
been intentionally omitted from the Bird APM-16. Experience using the Thruline
Wattmeter for transmitter tune-up, antenna matching, etc. will show that the
power ratio measurement is as useful as the standing wave ratio.
A trial is suggested – forget about VSWR for a few days and think in terms of
=
W
r
/ W
f
. The meter readings, W
r
and W
f
, give a useful, approximate picture of
the results without bothering to calculate the power ratio exactly. Consider
that, for an antenna matching problem, the main objective usually is to
minimize W
r
. Anything done experimentally to this end will be seen when the
element is in the reflected power position.
and
Where
= VSWR
and
= W
r
/ W
f
1+
1
–
----------------
=
1
–
1
+
------------
=
2
Содержание Thruline APM-16
Страница 15: ...Theory of Operation 5 Figure 3 Percent Reflected Power vs VSWR 1 0 8 0...
Страница 16: ...RF Directional Thruline Wattmeter Model APM 16 6 Figure 4 Percent Reflected Power vs VSWR 1 0 1 3...
Страница 24: ...RF Directional Thruline Wattmeter Model APM 16 14 Figure 8 VSWR Conversion Graph Reflected Power 0 2 20 0...
Страница 25: ...Operating Instructions 15 Figure 9 VSWR Conversion Graph Reflected Power 0 01 1 00...
Страница 27: ...Operating Instructions 17 Figure 10 Cable Length Wavelength Matching...
