Acom ACOM2100 - Continuous Carrier Modes Operation

14
- Look at the lower (Load Cap) scale and turn the lower (LOAD) knob in order to center the triangle
marker at the "!" mark.
- Release the PTT briey in order to disable the attenuator, then repeat both steps at nominal power.
Always nish by peaking with the TUNE knob
.
N O T E
Appearance of an arrow on either left or right TRI scale edges means that the LOAD
knob position is far off. To correct this, turn the LOAD knob to the prompted direction
until the triangle marker appears inside the scale eld.
I
_____
!_____
IIII
>____!_____
IIIIIIIIIII
_____!____<
IIIIIII
_____!__v___
IIIIIIIIIIIIIIII
_____v_____
no marker:
use TUNE knob for
max. P to get any
marker.
marker is a far left:
turn LOAD knob
pointer to right until
marker inside.
marker is a far right:
turn LOAD knob
pointer to left until
marker inside.
marker inside:
turn LOAD knob
slightly left to
center it.
LOAD is tuned:
turn TUNE knob to
peak Forward
Power & finish.
Fig. 4-1. Using TRI tuning aid
Please note that the TRI mark will not appear until at least 5W drive is applied, and at least 20W forward
power is achieved.
If, for some reason, matching cannot be accomplished successfully, check the BAND switch position and
proper antenna selection. Then check the antenna VSWR at the same drive frequency.
d) Tuning hints.
While turning the knobs, note that both tunings would be virtually independent. This is a benet of the
TRI. The plate-load resistance increases to the right and decreases to the left of the TRI center.
The scale center corresponds to the proper LOAD capacitor tuning, which presents an optimum load
resistance to the tube.
If you tune to the right, more gain will be obtained but less undistorted output power will be attainable.
You may prefer to use this tuning approach when your drive power is insufcient or when you need less
output but better efciency, for instance at heavy duty modes (RTTY, SSTV etc.) where less heat is
wanted (not only in the amplier but also in the transceiver).
Tuning to the left of the center would lead to the opposite: less gain and more power attainable. Of
course, this requires more drive power, more plate current, and more plate heat, which shortens the
tubes-expected life, as its cathode would be exhausted more quickly.
You might use the above off-center tuning hint also to compensate for mains voltage variations in order
to maintain tube efciency: tune to the right when mains is higher, or tune to the left if it is lower than the
nominal voltage. Please see S.2-2 (Mains Voltage Selection) for more than 5% deviation.
4-5. Continuous carrier modes
The maximum output power in continuous carrier modes such as RTTY etc. is 1500W. You may exceed
this limit for short periods (one minute or less), while adjusting the drive power for instance. Please have
in mind, however, that the mean output power should not exceed 1500W for longer periods.
For prolonged transmissions the amplier gain can drop between 5% and 10% during the rst minute
which is normal while temperature balance of the tube is achieved. You can easily compensate this by
increasing the drive power slightly. Once the drive power has been set, the output power remains stable
with the time for hours.
.