MFJ-1792/1793 Instruction Manual
Vertical Antenna
12
32- Secure Antenna to the base mount, by placing a U-bolt Saddle Clamp between the
fiberglass solid rod and the Aluminum wall. (see inside front cover) Line up the Saddle
Clamp with the 1/4" holes. Insert the U-Bolt through. Thread two 1/4" - 20 nuts and split
washers onto the U-bolt. Secure the U-bolt and the bottom 1/4"- 20 bolt.
33- Straighten up the antenna, and secure guy wires (
not permanently)
. Make the
grounding connection necessary.
34- Place the solder lug of the feedline under the Coupler 1 hose clamp at the base of the
antenna and tighten the hose clamp.
See Figure 6.
35- Antenna assembly is completed now, it can be tested using a transceiver on low power
or with an analyzer such as the MFJ-249, or the MFJ-259, then fine tuned before
mounting it permanently.
TUNING THE ANTENNA
Measure and record the frequency on which the lowest SWR occurs for the 80, 40 and 20
meter bands. The MFJ-1792 is tuned for lowest SWR either at the lower frequency of
each band or slightly below.
NOTE:
Make sure to disconnect the connection to the matching network before lowering
the antenna to tune the 80 or 40 meter bands. Failure to do so will damage the
matching network feed wire !!!
40 Meter Band:
The MFJ-1792 generally does not require tuning on the 40 meter band
. It covers
the entire 40 meter band with very low SWR. However, the location and the ground
system may cause the antenna to slightly detune. Retuning the antenna can be
accomplished by sliding Tube 5 into Tube 4 to decrease or increase the length of the
radiator, which in turn increases and decreases the frequency respectively. Use the
information below for your adjustment.
40 m: 1' of length equals
approximatly
200 KHz
80 Meter Band:
80 meter bands has narrower bandwidths. It should be tuned to the most desired section
of the band by shortening one or more spokes in the capacitance hat, from the inner side
according to the information given below.
