MFJ-269 Instruction Manual HF/VHF/UHF SWR Analyzer
17
Never apply dc, or more than 5 volts peak-to-peak voltage to the
FREQUENCY COUNTER INPUT
BNC jack.
In this mode the GATE button controls the frequency counter time window. As a general rule the longer the time
window the more accurate the frequency count. The accuracy of this counter is typically better than 0.05 %.
4.3 Main Modes (UHF)
4.3.1 Antenna System SWR (UHF)
The initial (opening)
“MAIN”
mode disables the Impedance meter. The analyzer display reads SWR referenced
to 50 ohms. The SWR meter functions normally. The display has a bargraph of SWR, as well as displaying the
SWR numbers. Overflow is set at VSWR>5:1.
4.3.2 Coax Loss (UHF)
A second
“MAIN”
measurement mode,
“Coax Loss”
, is reached by pressing the
MODE
button once. This
mode indicates the approximate loss of a 50 ohm feedline. The line must not be terminated, it must remain open
at the far end to measure line loss. An overflow indicator in the display (“less than” sign, LOSS<1.76dB) means
the loss can not be accurately determined.
The analyzer will return to the SWR measurement mode if the
MODE
button is pressed while in the
“Coax
Loss”
mode.
5.0 ADVANCED OPERATION
CAUTION: THERE IS A ‘‘UHF’’ SWITCH LOCATED AT THE UPPER LEFT-HAND
SIDE OF THE ANALYZER. THIS SWITCH SHOULD BE PRESSED AND
LOCKED FOR UHF OPERATION ONLY WHEN UHF OPERATION IS DESIRED
AND ONLY AFTER THE UNIT IS POWERED UP. FOR INFORMATION ON
UHF OPERATION, SEE SECTION 3.4
WARNING: Never apply RF or any other external voltages to the ANTENNA port of this
unit. This unit uses zero-bias detector diodes that are easily damaged by external
voltages over a few volts.
5.1 Forward
The advanced mode provides several special functions. Some functions are very useful, such as distance to fault
(HF/VHF) or transmission line length in degrees.