on to junior link techs and the mythology developed a life of its own. In the
following paragraphs, we examine some of these myths and seek to clarify the real
problems that led to the evolution of them.
Myth: Changing the NCS Will Always Solve Net Problems!
Changing the NCS may solve net problems, but only if the current NCS is
causing the problem. What is the problem? If data is not being received from a unit
because the current NCS has entered the PU number incorrectly, shifting NCS
functions to a station with the PU data entered correctly will solve the problem.
However, it would be easier if the current NCS were simply to enter the correct PU
numbers.
When the current NCS is using a radio set with poor receiver sensitivity and is
polling on top of picket responses effectively jamming the entire net, changing the
NCS is imperative. Also, if several units are not recognizing their interrogations
because NCS is out of range or in an RF propagation shadow, changing to a unit in
a better location should improve net communications.
Myth: Changing Frequency Always Solves Net Problems!
Here again is a myth that has some basis of fact. Changing frequency is a time-
consuming process. When all the procedures are not carefully followed, then
changing the frequency induces additional problems into the net. This myth
developed because improperly set switch positions and patch panel configurations
were often set to the proper position during the frequency changing process. When
the problem is connectivity on the current frequency, the proper action is to find a
better frequency.
Myth: More Power Improves Link Performance!
This is a myth. On the transmit side, the idea behind the myth is that keeping the
link HF transmitter tuned to maximum output power will result in maximum area
coverage. In fact, constantly outputting maximum power can lead to serious
RFI/EMI problems (on the ship doing so) and will not significantly increase the
signal propagation range.
The idea behind the myth on the receive side is that by keeping the HF receiver
audio output control maximized, receive quality improves. In fact, maximizing the
audio output saturates most data terminal sets. Saturation generally occurs in the
DTS at around 3 dBm. Signal inputs above this level actually increase receive data
errors.
Myth: Dummy PUs Improve Link Quality!
A dummy PU is an address insert into the polling sequence by the NCS for which
there is no live unit. Dummy PUs cause the net cycle time to increase and net
efficiency to decrease. The idea that the NCS must use dummy PUs for the link to
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