Conserving Power When Operating On Batteries; Internally Generated Rf Noise; Mars/Cap Coverage; Theory Of Operation - LDG AT-100Pro Operation Manual

relays, which means they only consume power when switching. When the AT-100Pro is idle, very little
current is drawn.
One of the biggest consumers of power in the AT-100Pro is the LED display. When operating
portable, you may choose to disable the LED display, as described in the section on Startup Options.
For the absolute highest level of power savings, you can even remove the DC power plug from the
AT-100Pro after it has found a tuning match, because the latching relays will maintain the tune setting
even with no power applied. Just remember to plug the AT-100Pro back in when it's time to re-tune.

Internally Generated RF Noise

The AT-100Pro is microprocessor controlled, and as such, generates a small amount of RF noise when
the processor is active. Normally, the processor is only active during transmit operation, so the noise is
not normally heard; however, if Peak mode is selected, the processor remains active for a moment after
key-up, to allow the LEDs to settle back down to zero. You may briefly hear some noise in your receiver
during this time. This is normal, and is noticeable the most when using CW in full break-in, with Peak
mode selected. In practice, this should not be much of a problem, as Peak mode is not very useful when
using CW.

MARS/CAP Coverage

The AT-100Pro provides continuous tuning coverage from 1.8 MHz to 54.0 Mhz, not just inside the
ham bands. This makes it useful for MARS or CAP operation, or any other legal HF operation.

THEORY OF OPERATION

Some basic ideas about impedance

The theory underlying antennas and transmission lines is fairly complex, and in fact employs a
mathematical notation called "complex numbers" that have "real" and "imaginary" parts. It is beyond the
scope of this manual to present a tutorial on this subject
understanding what the AT-100Pro is doing, and how it does it.
In simple DC circuits, the wire resists current flow, converting some of it into heat. The relationship
between voltage, current, and resistance is described by the elegant and well-known "Ohm's Law",
named for Georg Simon Ohm of Germany, who first discovered the principle in 1826. In RF circuits, an
analogous but more complicated relationship exists.
RF circuits also resist the flow of electricity. However, the presence of capacitive and inductive
elements causes the voltage to lead or lag the current, respectively. In RF circuits, this resistance to the
flow of electricity is called "impedance", and can include all three elements: resistive, capacitive, and
inductive.
The output circuit of a transmitter consists of inductors and capacitors, usually in a series/parallel
configuration called a "pi network". The transmission line can be thought of as a long string of capacitors
and inductors in series/parallel, and the antenna is a kind of resonant circuit. At any given RF frequency,
each of these can exhibit resistance, and impedance in the form of capacitive or inductive "reactance".

Transmitters, transmission lines, antennas, and impedance

4 For a very complete treatment of this subject, see any edition of the ARRL Handbook for Radio Communications (previously the Handbook For Radio Amateurs).
4
, but a little background will help in
PAGE 18