MFJ MFJ-207 User manual

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MFJ-207 HF/VHF SWR Analyzer
Thank you for purchasing the MFJ-207 HF/VHF SWR Analyzer.
The MFJ-207 gives you a direct readout of your antenna's SWR
without the need for formulas or indirect readings. The MFJ-207
can also be used to adjust a tuner to match your antenna without
the need for transmitting. The frequency coverage for the MFJ-207
is approximately from 1.75 MHz to 30 MHz in five bands. This
provides a very smooth reading of SWR at high frequencies. The
coverage for each band may slightly vary from the coverage labled
on the cover. The bands and coverage are:
BAND A 1.75 - 3.00 MHz
BAND B 3.00 - 5.00 MHz
BAND C 6.50 - 11.70 MHz
BAND D 11.65 - 20.00 MHz
BAND E 18.00 - 30.00 MHz
The MFJ-207 requires the optional MFJ-1312B power supply
adapter or a nine-volt transistor battery. A power supply may
also be used by connecting a 2.1 mm plug to the cable with
the positive wire connected to the center pin and the ground
wire connected to the outer pin.
************************************************************ *
NOTE: If you use a battery with the MFJ-207, use * an ALKALINE
nine-volt battery.
************************************************************
To install batteries, remove the screws holding the cover
onto the case. Insert the batteries into the battery holder.
Tuck the battery snap wires out of the way so they do not
interfere with the tuning capacitor rotation. Reinstall the
cover and screws. The dial calibration is only approximate and
is for reference only. A frequency counter can be connected to
the FREQ. OUT jack (RCA phono) to get a more accurate reading
of the frequency. As an alternative to a frequency counter,
you can zero beat the output with an HF receiver. See
APPENDIX A.
USING THE MFJ-207 HF/VHF SWR ANALYZER
Your MFJ-207 HF/VHF SWR Analyzer has many uses. It can be
used to find the resonant frequency of your antenna, to find the
SWR of your antenna at a particular frequency, and
find the frequency at which your antenna has the lowest SWR. You
can also use the SWR Analyzer to adjust your antenna to a low SWR
and to adjust an antenna tuner to match the transmitter to the
line.
Measurement of the antenna's SWR is done.right at the
input to the transmission line. There is no need to climb the
tower and measure the SWR at the antenna. Using the chart in
Figure 3, and knowing the line loss for your transmission line
and the SWR at the line input, you can determine the SWR at
the antenna, regardless of line length.

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I. Measure the antenna's SWR at a particular frequency.
1. To check the SWR of your antenna, connect the
antenna with a PL-259 connector to the ANTENNA
connector on the MFJ-207.
NOTE: If you are using coax as your feedline, connect
the coax directly to the SO-239 (UHF) connector
marked ANTENNA.
If you are using an open-wire feedline, wire the
feedline to a PL-259 connector, then attach it to
the ANTENNA connector of the MFJ-207.
2. Set the BAND switch to the appropriate band.
3. Adjust the frequency dial of the SWR ANALYZER to
the frequency at which you want to check the SWR.
4. Read the SWR from the meter.
This is the SWR at the INPUT TO THE TRANSMISSION
LINE looking toward the load (antenna). To determine the
SWR at the antenna, use Figure 3 in APPENDIX D.
NOTE: If the SWR at the transmitter is 1:1, then the SWR
at the antenna is 1:1.
5. Using steps 1 through 4, you can make a plot of SWR
versus FREQUENCY for your antenna. Just plot the SWR
at many different frequencies. APPENDIX B has an SWR
vs. FREQUENCY chart (Figure 3).We suggest you make
photocopies of this chart so you can use it for
several antennas.
NOTE: It is advisable to take readings on several bands to
determine the frequency at which the lowest SWR
occurs. The SWR can be low at several different
frequencies, but there should only be one frequency
that shows the LOWEST SWR. That frequency will be the
natural resonant frequency of the antenna.
II. Find the frequency at which the antenna has the lowest
SWR.
1. Connect the antenna to the MFJ-207 as in step I.
2. Turn the BAND switch to the appropriate band. 3.
Adjust the TUNE control throughout its range until
the SWR meter reads its lowest value. Read the
frequency on the frequency meter. Read the SWR on
the meter.
4. If you do not obtain a low SWR on any frequency,
turn the BAND switch to another band and repeat Steps
1-3 above. Don't be surprised if your antenna
does not show a 1:1 SWR on any frequency. Many antennas
can be tuned to obtain a 1:1 SWR, but will never show a 1:1
SWR without an antenna tuner.

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NOTE: The antenna may have a low SWR at more than one
frequency. For instance, an antenna that is
resonant in the 40 meter band is usually also re-
sonant in the 15 meter band.
III. Adjust the antenna for 1:1 SWR.
1. Turn the BAND switch to the appropriate band.
2. Turn the frequency TUNE knob until the pointer is on
the freq at which you want to tune the antenna.
NOTE: For accuracy, use a frequency counter attached to the
COUNTER output on the SWR ANALYZER or zero-beat
against the reciever. See Appendix A.
3. Read the SWR on the meter. If the meter reads other
than 1:1 SWR, adjust the antenna until the antenna
reads 1:1 SWR (or lowest value
obtainable).
NOTE: The MFJ-207 can tell you whether the
antenna elements are too short or too long.If you find the antenna'
low, then the elements are too long. If the resonant
frequency is higher than you want then the elements
are too short.
If you are adjusting an antenna for the first time, it is
recommended you start with elements a little too long, then
shorten to resonance. Again, the SWR for your particular
antenna may never get as low as 1:1. Adjust for the lowest
reading.
IV. Using the MFJ-207 to adjust an antenna tuner.
1. Connect the antenna to the antenna tuner connector
marked ANTENNA.
2. Connect a coax cable between the tuner's TRANS
MITTER connector and the MFJ-207's ANNTENA
connector. (See Figure 1.) This should be a
2-3 foot length of RG-58 or RG-8.
3. Turn the BAND switch to the appropriate band.
4. Set the frequency dial to the desired operating
frequency. Adjust the tuner's controls until the
meter on the MFJ-207 indicates 1:1 SWR (nulls).
5. Disconnect the MFJ-207 completely and connect the
tuner to the transmitter.
6. Turn the Band Switch to OFF when finished .
***********************************************************
*CAUTION *
* Never transmit through the MFJ-207. Take the MFJ-207
*com
p
letel
y
out of line before transmittin
g
!
* Dama
g
e to
y
our MFJ-207 will result if left in line.
***********************************************************

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We recommend using the MFJ-1702 coax switch as in the
diagram below:
Figure 1 - Hook-up for Using Analyzer to Tune Antenna Tuner.
WARNING - Never transmit while the MFJ-1702 coax switch is
switched to A if the xmitter is connected to B.
Damage to your radio can occur.
TRANSMIT ONLY WHEN THE COAX SWITCH IS SWITCHED TO
THE CONNECTOR TO WHICH THE XMTR IS CONNECTED.
If the XMTR input is on B, then transmit only
when the coax switch is in position B.
If the XMTR input is on A input, transmit only
when the coax switch is in position A.
The center conductor of the UNSELECTED coax
position is grounded, so transmitting into B
while the switch is in position A will cause
you to be transmitting into a dead short to
ground.
NOTE: MFJ Enterprises, Inc. will NOT be liable for
any damage to your radio or other equipment due to
improper connection or use of the MFJ-1702 coax
switch.

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APPENDIX A
HOW TO ZERO-BEAT THE MFJ-207 AGAINST THE RECEIVER
The FREQ. OUT port on the MFJ-207 has a sine wave output
which can be used to accurately check the frequency at which
the MFJ-207 is working.
To zero-beat the 207 against the receiver, loosely couple a
wire from the RCA jack (Freq. Out) to the antenna connector
on your radio.
First, try a small length of wire from the FREQ. OUT
connector of the SWR ANALYZER. Just leave it dangling free,
not touching the ANTENNA input of the reciever. Place the far
end of the wire near the reciever input but do not connect
to the input unless you simply cannot hear the signal at all
in the receiver. The output of the SWR ANALYZER is high.
Damage to some radios may occur with a direct connection,
so you assume all risk involved in making a direct connection
to your radio.
Turn the radio on and tune to the frequency in question.
For example, if you want to check your 40 meter dipole on
7.235 MHz, set the radio for 7.235 MHz. Turn the RF and
audio down because the signal coming out of the MFJ-207 is
pretty strong. Put the radio in the CW mode. If you have a
BFO adjustment on your radio, be sure to set the BFO to ON
and to 0 (zero).
Set the MFJ-207 to BAND B. Adjust the TUNE dial on the MFJ-
207 until you start hearing a tone in the radio's speaker. As
you turn the TUNE dial, the frequency will start at a very
high pitch, then decreases to zero pitch. The point where
the tone goes to zero Hertz is the "zero
beat". That means the radio frequency is set to the exact
frequency of the MFJ-207.
Now make a note of where the dial is set to on the MFJ-207 so you
can re-set the frequency if you accidentally bump the TUNE
control.
You can now disconnect the wire and re-connect the antenna to
the MFJ-207.

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APPENDIX C
Facts About Transmission Lines and Line Loss.
The MFJ-207 should be connected to the input to the trans-
mission line looking toward load. You do NOT have to know
the length in wavelength of your transmission line, but you
do need to know the number of feet (or meters) and the loss
(in dB) for the length of the transmission line you are
using. Using the SWR/Line loss chart below you can readily
determine the SWR at the antenna. The most important con-
sideration for any antenna system is probably the loss in the
transmission line. The less loss, the better. Two important
points about transmission lines need to be understood:
1. On a LOSSLESS transmission line, the SWR read at the
transmitter is the same as the SWR at the antenna. For
any line with loss the SWR is greatest at the antenna and
minimum at the transmitter.
2. Regardless of the losses in the transmission line, if the
SWR at the transmitter is 1:1, then the SWR at the
antenna is 1:1, but if there is ANY SWR at the input to
the transmission line, there is a higher SWR at the
antenna (assuming anything but a lossless line). Let's go
through a practical example:
Let's say you are using RG-58/U which has a loss of 2.3
dB at 30 MHz per 100 feet. You are using only 50 feet of
cable, so your loss when matched at the transmitter is
1.15 dB at 30 MHz.
Go to Figure 4 in APPENDIX D and find the 1 dB loss line
which curves up and to the right.
Now assume you are using the MFJ-207 and find that the
lowest SWR you can get on our antenna is 2.0:1.
Follow the 1.15 dB line (between the 1 dB line and the 2
dB line) down to the point it reads 2.0:1 on the
horizontal axis (SWR at transmitter).
Looking at the vertical axis we can see that the point
corresponds to an SWR of about 2.5:1 on the vertical
axis.
Reading this chart correctly tells us that with 50 feet
of RG-58/U that has a loss of 2.3 dB per 100 feet at 30
Mhz and a line input SWR of 2.0:1, the SWR at the antenna
is 2.5:1.
By the way, the 2.0:1 SWR at the load only adds about .225
dB of loss to the already matched 1.4 dB of loss for a
total loss of 1.625 dB. (See ARRL Antenna Book.)