17
•
Repeat the above steps, while gradually increasing the input drive power, until the overdrive indicator
just starts turning on. Now the DX-1d is tuned for operation at full power on that particular operating
frequency.
NOTES:
1. The maximum power is obtained from a DX-1d when:
onset of the overdrive indication
PLATE is tuned for maximum output power, maximum screen current Ig2 and minimum plate current, Ip
Ig2 indicator shows 2 or 3 red LEDs.
2. The above conditions will also give the best linearity.
3. During the preliminary tuning, switch PTT on and off several times, to allow time for tube cooling. The tube
dissipation (at a given drive level) is minimum when tuning is optimum. In short, be brief, with tuning "bursts".
4. Preliminary tuning, as described above, is only necessary when operating for the first time in a certain band.
When the final settings for PLATE and LOAD have been found for the particular working conditions -
especially the antenna used, note your settings on Table 1. The new settings will normally differ to some extent
from the ones indicated, depending on the "purity" of your antenna load.
10.1.3
Final tuning
Once the preliminary tuning has been done for each band / antenna combination, the values found for PLATE
and LOAD can be used for final tuning, with no need to repeat the preliminary tuning every time.
Tuning for full power
•
Start with low drive level and the PLATE and LOAD knobs in the known initial positions
•
Put PTT ON and increase the power (fairly quickly), to the onset of the overdrive indication. If the
screen current (red Ig2) goes too high, adjust LOAD, by turning the knob to the left (increasing the
load).
•
Adjust the drive level and LOAD until the overdrive indicator is just about to turn ON, and at the same
time Ig2 shows two or three red LED's ON.
•
Fine tune PLATE for maximum output and maximum Ig2. Repeat the step above if required.
Tuning for less than full power
•
Start at low power, with the initial values for PLATE and LOAD
•
Put PTT ON and apply drive until the output is about 1/2 of the desired power.
•
Adjust LOAD for maximum output. Most likely, the knob will have to be rotated to the right, towards
higher numbers on the dial.
•
Adjust PLATE for maximum output
•
Apply more power
•
Repeat the 3 steps above until the required power is achieved. If screen current is indicated by Ig2, is
should, display one to three red LED's. Maximise this Ig2 indication (and the output power at the same
time), by tuning PLA TE
Please note that the tuning at lower power is different from the setting at full power.
•
If the output goes higher then desired, reduce the drive
and re-tune
.
Never reduce the output by de-
tuning the amplifier
!
