MFJ-266C HF/VHF/UHF Antenna Analyzer
Instruction Manual
Version 2A
10
2012 MFJ Enterprises, Inc
(4.) Rotate the
Tune
knob to find the lowest
SWR
reading and write it
down.
(5.) Rotate
Tune
to either side of minimum SWR and note the
2:1 SWR
points.
*When testing large ungrounded antenna systems such as HF dipoles,
momentarily short the feedline center pin to ground to bleed off static
buildup before connecting to the analyzer.
6.4 SWR, Bandwidth, and Resonance
The amateur-radio industry's standard for maximum SWR is 2:1 (1.5:1 for
commercial 2-way).
Most modern transceivers operate safely and deliver full
power within this mismatch range. The antenna
bandwidth
is the frequency
interval between its two 2:1 SWR points. This specification, along with
minimum SWR
and
minimum SWR frequency,
is often included on antenna
specification sheets. Note that
minimum SWR
is sometimes wrongly
confused with
resonant frequency.
The technical definition for
resonance
is
t
he frequency where inductive and capacitive reactance cancels, leaving a
purely resistive load (
±
j = 0)
. The minimum SWR and resonant frequencies
may be close, but they rarely coincide.
13.9
14.0
14.1
14.2
14.3
14.4
1.5
2.0
1.0
Min. SWR Freq.
Bandwidth
Lower 2:1 Freq.
Upper 2:1 Freq.
Min. SWR
6.5 Antenna Tuning
Where possible, make adjustments to your antenna that will yield SWR
readings under 2:1 over the frequency range where you normally operate. If
the minimum-SWR frequency measures low in the band (or below the band
edge), your antenna is probably too long and will need to be shortened. If the
Minimum SWR frequency is too high, it should be lengthened. To calculate
the required change in length:
(1.) Write down the
desired minimum SWR frequency
(ex: 14.200 MHz)
(2.) Use the analyzer to measure the present
minimum SWR frequency
(ex:
14.050 MHz)
(3.) Divide the present
frequency
by the
desired frequency
(ex 14.050
÷
14.200 = .989)
