Palstar AT5K Owner's manual - page 12
Operating Your AT5K cont’d 12
1-800-773- 7931 W W W .PALST AR.CO M
7. Key your transmitter and adjust the
power level for a reading of 100-150
watts on the FORWARD scale. Adjust
the INPUT, OUTPUT and INDUC-
TOR controls for a minimum
REFLECTED reading while maintaining
a FORWARD reading of 100-150
watts using your transmitter power
control. Use the supplied chart of ap-
proximate tuning control locations for
the different bands located at the back
of the manual.
8. Read the SWR on the red scale at
the point where the two needles inter-
sect. Repeat TUNING the input and
antenna controls until the lowest SWR
reading is obtained.
This procedure takes patience the
first time. The input and antenna
controls vary the capacitors and
provide fine adjustments. The roller
inductor crank control provides
coarse adjustment.
9. When you have tuned your antenna
to the best SWR, record the settings
of the INPUT, ANTENNA and IN-
DUCTANCE controls on the chart
above for future reference. When you
retune, use these settings as your
starting point.
Notes
1. An SWR of 1:1 is best, but an
SWR as high as 2:1 may be acceptable.
Check your transmitter/amplifier man-
ual for details.
2. If you cannot get an acceptable
SWR, lengthen or shorten your an-
tenna and/or feedlines and retune.
3. Very high or very low impedance
loads are to be approached with extra
caution especially when you are going
to use high power and the use of an RF
analyzer would be advisable (e.g. the
Palstar ZM30 Antenna Analyzer) to
check and understand the kind of load
you attempting to use.
4. If you get low SWR readings at
more than one setting, use the setting
that gives:
- highest FORWARD power reading
- lowest REFLECTED power reading
- uses the largest capacitance (highest
number) on the ANTENNA control.
It is important to remember that con-
sistent with low SWR indicated on the
tuner meter you must have and adjust
for:
- the largest capacitance (highest num-
ber) on the output control to keep the
losses low and the voltage that would
appear on the antenna capacitor within
the 5kV rating;
- if you hear a spitting sound while
tuning at high power you are probably
tuning into an impedance that is on the
low side (20W - 40W). Please see the
troubleshooting section for more de-
tailed instructions.
- for example: at 1500 Watts into a
25Ω load @ 3.5Mhz will produce the
following:
Ant Cap Inductor Voltage Loss
100pF
11.7 µH 4550
16%
200pF
6 µH
2400
8%
300pF
4 µH
1600
6%
In the first instance the tuner will arc
and suffer almost 16% loss of which
80% will be dissipated in the roller
inductor.