User Manual

Page 16 of 34
- the SWR indication of the transceiver must be below 1.2:1.
Enter menu MEASURE and check-up additionally:
- the drive power from the transceiver must be between 20 and 30W;
- PA BIAS must be between 2.5 and 2.9V (typically 2.8V);
- PA TEMPERATURE must be between the ambient and 80ºC (176ºF) depending on the power level
and the duration of transmission.
When possible, listen to the quality of the amplified signal using a monitoring receiver or ask some regular
correspondents for signal assessment and comparison with and without amplifier.
g) 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 its set up.
It is likely to run into problems of the type ”itching (tingling) from the metallic objects” due to the stronger
radiated RF field. It could affect the operation of your station or systems outside it, if the latter are too sensitive
– typical examples are the microphone, the Morse keyer, the computer keyboard / mouse, as well as domestic
radio / TV receivers, Hi-Fi, intercom or telephone setups and others.
For instance, induction of RF currents into the microphone, Morse keyer or computer keyboard, may lead to
rough distortions in the peaks or self-oscillation in SSB mode, “sticking” or breaking off the signals from the
Morse keyer, or garbles on the computer screen, coming from the keyboard. For the elimination of similar
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 the antennas themselves as well as of their feeding;
- in case you use asymmetric antennas (GP and similar) install as many radials as practical (a more
developed counterpoise system);
- ground the coaxial cable shield additionally on at least one spot between the antenna and the shack
or if it is possible run the greater part of the feed line under ground;
- add current BALUN transformers in the coaxial feeders at the antenna itself, as well as at the feeder
entering the building (although this may look unnecessary at GP);
- take away as far as possible (also by height) the radiating elements of the antennas from the
premises where the affected apparatus is located; in this sense, asymmetrical antennas without a
feeder (type Long Wire, Windom, and other similar) may cause more interference because their
radiating element begins immediately from the shack (it is the feeder itself);
- if the use of asymmetrical directly fed “wire” antennas is inevitable, use mainly half wave or half wave
multiple – they have a high input impedance, operate respectively with a small current in the feed
point, and in the grounding of the shack; thus you can reduce the strength of the disturbing RF fields
in the whole 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 quarter-wave and
multiple to quarter-wave antennas 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;
- to reduce the RF impedance of the grounding connections prefer sheet metal stripes instead of
flexible braids;