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Enter menu MEASURE and check-up additionally:
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the drive power from the transceiver must be between 20 and 30W;
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PA BIAS must be between 2.5 and 2.9V (typically 2.8V);
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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
possible you might find tingling from 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 dots or dashes from the
Morse keyer, or garbles on the computer screen, coming from the keyboard or mouse. For the elimination of
similar problems we recommend that you take the following general measures:
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minimize the radiation from the feed lines by reducing the common mode currents in them; improve the
balance of the antennas themselves and how they are fed;
- in case you use asymmetric antennas (GP and similar) install as many radials as practical (a more
developed counterpoise system);
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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 seem 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, simple 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 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);
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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 sheet metal strips instead of flexible braids
are preferred;
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thread ferrite beads with medium permeability (800-4000) over the power cord, the feeder and the signal
cables leading to the affected devices (TV etc); there are suitable “split” ferrites on the market for this
purpose with different sizes, shapes and parameters, inserted in locking plastic shells, which do not need
to be threaded through the connectors on the cable ends and are simply put and locked over it; besides