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APPLICATION INFORMATION
Mobile Operation
The Z-817H is perfectly suited to mobile operation. It can be installed under the dashboard
along with the transceiver, or mounted remotely. The only requirement is that the tuner remains
dry.
MARS/CAP Coverage
The Z-817H provides continuous tuning coverage over its specified range; not just in the ham
bands. This makes it useful for MARS or CAP operation, or any other legal HF operation.
Operation with a PC / CAT
Although the Z-817H uses the transceiver’s CAT port for tuning control, the Z-817H is
designed to allow the user to continue to use the CAT interface with the transceiver for PC
control, also.
If PC control of the radio is desired, simply connect a CT-62-compatible cable from the PC
to the 8-pin mini DIN jack marked “
Compute r
” on the rear of the Z-817H.
Any rig control software on the computer must be set to use the 38,400 baud rate, as this is
the communication rate used by the Z-817H for controlling the radio.
The Z-817H monitors the
Computer
port for activity before beginning any tuning cycle.
Only when the CAT line is idle for a period of time will the Z-817H take over control of the
CAT line in order to perform a tuning cycle. When the tuning cycle is complete, control of the
CAT interface is returned to the PC.
This procedure is completely automatic, and is transparent to the user. Simply hook up a PC,
and use the rig control software as normal. Press the
TUNE
button on the Z-817H when tuning is
desired. Some rig control software will detect that the radio is no longer communicating with the
PC during tuning. This is normal, and communications with the PC will resume once the tuning
cycle is complete.
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
2
, but a little background will
help in understanding what the Z-817H 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.
2 For a very complete treatment of this subject, see any edition of the ARRL Handbook for Radio Communications (previously the Handbook For Radio Amateurs).
