Palstar AT5K Owner's Manual - page 14
14
Operating Your AT5K cont’d
4. Any time a new or different antenna is connected, it is necessary to repeat
the tuning procedure for the new antenna.
Troubleshooting
You hear a spitting sound while tuning your AT5K at high power.
You are probably tuning into an impedance that is on the low side (20Ω – 40Ω).
In this event, either reduce transmitter/amplifier power to a lower setting or
change to a higher antenna impedance by using a different antenna or modifying
the existing antenna.
Also, try to find the highest capacitance setting (i.e. closer to 100 on the dial) on
the output knob. This will probably require re-adjustment of the inductance
setting.
An antenna capacitance setting that is too low under these conditions will result
in excessivly high voltages, high losses, and poor efficiency.
For example: at 1500 Watts into a 25Ω load @ 3.5Mhz will produce the
following:
In the first instance the tuner will arc and suffer almost 16% loss of which 80%
will be dissipated in the roller inductor.
8 Ω − 15 Ω
Ω − 15 Ω
Ω − 15 Ω
Ω − 15 Ω
1000 watts (all bands)
15 Ω − 25 Ω
Ω − 25 Ω
Ω − 25 Ω
Ω − 25 Ω
1500 watts (all bands)
25 Ω − 50 Ω
Ω − 50 Ω
Ω − 50 Ω
Ω − 50 Ω
3500 watts (all bands)
50 Ω − 2000 Ω
Ω − 2000 Ω
Ω − 2000 Ω
Ω − 2000 Ω
160M — 3500 watts
80M - 15M—3500 watts
10M — 1500 watts (29.5 MHz max)
Power Specifications
(assuming single tone key down)
Antenna Impedance
Max Power Rating
Output Cap
Inductor
Voltage
Loss
100pF
11.7 µH
4550
16%
200pF
6 µH
2400
8%
300pF
4 µH
1600
6%