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the size, consider the frequency range in which the offered ferrites are effective – normally they are
optimized for suppression of interferences on HF (with larger permeability), with medium permeability for
HF-VHF or with low permeability - only the VHF range. The latter are ineffective for HF;
-
whenever possible use shielded cables and ground their shields at both ends;
- screen (at least partly) the disturbed apparatus, for example, put under the keyboard, the mouse, the
desk microphone or the Morse keyer a large metal sheet, connected to the grounding system of the
shack;
-
the addition of even quite simple low pass L/C or R/C filters directly to the disturbed inputs or outputs of
the apparatus is very effective, provided it is practically applicable.
Last but not least, have in mind that the benefit of the above measures is two-fold. Firstly - they reduce the
interferences from your transmissions to the ambient environment and secondly - they reduce the background
noise floor for your reception. Practically, with no great efforts, implementing the above measures, you can reduce
the background noise floor with one or more S-units across the different bands. This will allow you not to miss
weaker stations, which will hear you because of your increased transmission power.
4. OPERATION WITH THE AMPLIFIER
4-1. Change of modes RX / TX and Operate / Stand-by; option AUTO OPERATE
a) In
Stand-by
mode, as well as with un-powered amplifier, receiving and transmitting with the
transceiver is implemented via RF by-pass between RF INPUT and RF OUTPUT of the amplifier. At
transmission in Stand-by, RF power of the transceiver is not amplified by the amplifier, the control
KEY-IN input does not influence over its operation, and the KEY-OUT output (S. 2-3(c)) follows the
state of the KEY-IN input unconditionally.
b) In
Operate
mode the final stage of the amplifier is powered and it is fully functioning; the receive-
transmit (RX / TX) direction is controlled by the KEY-IN input:
- at open KEY-IN (Operate/RX mode), the transceiver receives the signals from the antenna through the
same RF by-pass path between RF INPUT and RF OUTPUT through which receiving is done with
amplifier turned off or in Stand-by mode;
- at grounded KEY-IN (Operate/TX mode) the amplifier input relay connects the RF INPUT connector
(drive from the transceiver) toward the final stage input and the output relay feeds the amplified signal
from the final stage output to the antenna through the RF OUTPUT connector.
C A U T I O N
In order to provide time for the relays and the final stage in the amplifier to
switch safely from receive to transmit, the transceiver should provide a
dead time i.e. must “notify” the amplifier in due time grounding its control
KEY-IN input not later than 10ms
before
feeding drive power toward the
amplifier RF input. Otherwise, the “HOT SWITCHING ATTEMPT”
protection will trip.
In Operate mode the KEY-OUT output (S. 2-3(c)) follows the state of the KEY-IN input only after all conditions for
safe transmission have been satisfied and found OK by the amplifier control unit. The KEY-OUT output duly
disables transmission, if this is inadmissible or there is a potential risk for the amplifier or the transceiver.
The two modes -
Operate
and
Stand-by
- may alternatively be changed in three different, independent ways as
described below:
-
manually (locally) – by successive pressing the OPR/STB button – Fig. 3-2;
- remote control – through the respective command “OPR” or “STB”, received through the serial RS232
Interface;
-
automatic control – if the AUTO OPERATE option is activated – see next item and S. 5-4(b).