MFB VHF 3dB SERIES SPECIAL
TUNING INSTRUCTIONS
To optimize your VHF 3dB gain base station antenna, we
have designed a special top rod tuning section. This high
quality stainless steel whip has been factory tuned for the
lowest frequency in your ordering band.
For example:
The
MFB1503 will be factory tuned to 150 MHz.
DO NOT LOSE YOUR FACTORY TUNED TOP ROD!
If you do, you will need to trim your own rod starting at
about 27" for 144 MHz using a thru line watt meter to check
for lowest VSWR.
To "fine tune" the antenna to your exact operating frequen-
cy, follow these simple steps:
1. Noting that the operational bandwidth of the antenna is
about 5 MHz at 2.0:1 VSWR, choose your desired fre-
quency. You may either tune the antenna to your exact
frequency or tune it to the center of two or more frequen-
cy bands.
2. Using the cutting chart provided, trim the top rod (about
one inch per 1/2 MHz). This may be done with side cut-
ters or with a grinding wheel. If possible, check tuning
with a watt meter and the antenna mounted in as similar
a place to its actual location as possible.
3. Tighten the rod securely with the two set screws provided
before mounting the antenna.
For Example
If you have ordered an MFB1503 (150-156 MHz) antenna
and you wish to tune its center frequency to 153 MHz, trim
the top rod by approximately 5-1/8", according to the chart
below. Check with a watt meter for greater accuracy.
Remember, always make the first cut a little long to
avoid over-cutting the rod.
Cutting the rod too long or
short will move the antenna outside of its desired frequency
range resulting in a high VSWR (above 1.5:1) and degraded
gain performance.
MOUNTING HINTS
1. Always mount your base station antenna as high and
clear of surrounding objects as possible.
2. Use extreme caution when working near telephone and
electrical power lines. Always mount antennas at least
twice the length of the antenna away from power lines.
3. Always insulate your connectors with tape, silicone or
other weather proof materials for long life and trouble free
operation.
4. When side mounting to a tower, make sure that your
antenna is at least 24" from tower legs or other antennas.
5. Some antennas are equipped with drain holes, either on
the side of the aluminum sleeve or on the bottom bush-
ing, next to the connector. When mounting, be careful not
to seal the hole, as this will prevent water from escaping.
MFB VHF 3dB SERIES
MFB VHF SERIES
PART NUMBER
FREQUENCY
RANGE
FACTORY TUNED
FREQUENCY
3 dB GAIN
MFB1443
144-150 MHz
144 MHz
MFB1503
150-156 MHz
150 MHz
MFB1563
156-162 MHz
156 MHz
MFB1623
162-168 MHz
162 MHz
MFB1683
168-174 MHz
168 MHz
MFB2203
220-225 MHz
220 MHz
Example:
The dark line indicates that to tune an MFB1503 to 153 MHz
(3 MHz shift), you must trim 5-1/8” from the total rod length.
Note: The MFB UHF, 800 MHz and 900 MHz antennas do
not require any tuning.
Part #: MIS-MFB-3 REV B
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Frequency Shift (MHz)
Length To Trim Rod (inches)
