Acom 2020S, Руководство пользователя, Страница: 36 / 76

User's Manual | ACOM 2020S | 1.8-54 MHz Linear Power Amplifier
Page 36 of 76 | S e c t i o n FIRST POWER-ON, CONTROL SYSTEM, AND INITIAL CHECK June 2022
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 1500 W.
Upon reaching 1500 W forward power check the following parameters (continuous carrier operation):
•
The reflected power must not exceed ~166 W (for SWR 2) or better still to be below 60 W (for
SWR 1.5);
f) Elimination of electromagnetic compatibility (EMC) problems
If you use powerful 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 antenna feeders by reducing the common mode currents in
them, and improving the balance of antennas;
•
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;
•
Place as far away as possible (also by height) the radiating elements of antennas from the
premises, where the affected devices are located. In this sense, asymmetrical antennas
without a separate feeder (Long Wire, Windom, and similar) may cause more interference
because their radiating element begins immediately from the shack (part of it is the feeder
itself);
•
If the use of asymmetrical directly fed "wire" antennas is inevitable, use mainly half wave or
half wave multiple lengths - they have a high input impedance, operate respectively with a
small current at the feed point, and in the grounding of the shack. Thus, you can reduce the
strength of the disturbing RF fields more than 10 times (at the same radiated power)
compared to the case with quarter-wave and multiple to quarter-wave antennas of this class -
you should avoid them because they have a low input impedance and operate with a large RF
current in the grounding system and in the power supply network respectively, i.e., they
create stronger disturbances (RFI);
•
Improve the RF grounding system: use the shortest and widest possible metal strips for the
connections to ground and between the different gear in the shack. Connect one or more
counterpoises (sized for the problematic band) to the feeder shield at the point, where it
enters the building, and the same point - with the possibly shortest and widest connections -
to the grounding system: this is a very efficient measure, in particular if the shack is located
on a high floor above ground;