User's Manual | ACOM 700S | 1.8-54 MHz Linear Amplifier
May 2021
S e c t i o n FIRST POWER-ON, CONTROL SYSTEM, AND INITIAL CHECK | Page 25 of 52
•
RX mode must change to TX;
•
The reflected power must read below 20 W;
•
The forward power must read between 20 and 150 W with minimum drive power from the
transceiver (between 1 and 5 W).
If the above test goes normally, push briefly the PTT once again, this time watching the transceiver's SWR
reading (i.e. the input SWR of the amplifier) - this must be below 1.2:1.
e)
Setting of drive level and typical operation
After successfully passing of the above tests push PTT or CW key for several seconds, watching the forward
and reflected power. Increase the drive power until the forward power bar graph and digital readout reach
700 W.
Upon reaching 700 W forward power check the following parameters (continuous carrier operation):
•
The reflected power must not exceed ~78 W (for SWR 2:1) or better still to be below 28 W
(for SWR 1.5:1);
•
PA DC CURRENT must be between 23 and 30 A; it is normal that the current varies within
these limits when changing operating frequency and antenna impedance;
•
PA DC VOLTAGE must be within 42-44 V;
•
The transceiver's SWR reading must be below 1.2:1.
Enter the MEASURE menu (see
) and check:
•
Т
he drive power from the transceiver must be between
22
W and
29
W;
•
PA BIAS, which must be between 2.4 and 2.8 V;
•
PA TEMPERATURE, which must be between the ambient and 95
o
C (203
o
F), depending on the
power level and the duration of transmission.
f)
Elimination of electromagnetic compatibility (EMC) problems
If you use an amplifier for the first time in your shack, you may need to make some improvements in the
setup. It is possible you might experience tingling from metallic objects due to the stronger radiated RF
field. It could affect the operation of your station or systems outside, if they are too sensitive - typical
examples are the microphone, CW keyer, computer keyboard or mouse, as well as TV receivers, Hi-Fi,
intercom or telephone setups and others.
For instance, induction of RF currents into the microphone, CW keyer or computer keyboard, may lead to
distortion in the peaks or relaxation oscillation in SSB mode, "sticking" or breaking off the dots or dashes
from a Morse keyer, or garbling computer screen images. For the elimination of such problems, we
recommend that you take the following general measures:
•
Minimize the radiation from the feed lines by reducing the common mode currents in them,
improve the balance of antennas and feedlines;
•
In case you use asymmetric antennas (GP and similar) install as many radials as practical (use
a well-developed counterpoise system);
•
Add current chokes on the coaxial feeders;