Page 2
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.
To Next Page
Loading...
