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MFJ-1795 Vertical Antenna
INTRODUCTION
The MFJ-1795 HF antenna was designed to provide portable or permanent operation from
restricted locations. When combined with the MFJ Ground-Coupled™ Portable Antenna Base or
other suitable grounding system, such as radial system, the result is a small vertical antenna
under 10 feet in height.
The reduction in size is accomplished by adding separate loading coils and capacitance hats for
each band at the top of the antenna. The efficient end loading coils are wound on fiberglass
forms. The high quality materials and construction of the HF loading system allows a maximum
power rating of 1500 watts SSB PEP on 40, 20, 15 and 10 meters.
The power rating of this antenna varies from band to band. The PEP ratings are primarily
determined by the voltage breakdown of the components, while the CW ratings are generally
determined by the components heating.
The following chart lists the power rating and the 2:1 VSWR bandwidth of this antenna:
Band
40m
20m
15m
10m
The weight and wind load of this antenna are 10 pounds and approximately two square feet
respectively.
WARNING: Improper installation and assembly can be hazardous! Read
these instructions thoroughly before attempting to assemble, install, or
operate this product! High power transmitting devices produce voltages that
can cause severe burns or other injuries.
CHOOSING A LOCATION FOR THE ANTENNA
The best performance on receiving and transmitting will be obtained by mounting the antenna in
a clear location above or away from buildings, towers, feed-lines, utility wires, and other
antennas. While your own ingenuity and particular circumstances will determine the final
mounting method, we will pass along a few ideas for both permanent and portable installation.
MFJ-1795 Vertical Antenna
Power
CW
SSB
RTTY
700
1500 500
1250 1500 750
1250 1500 1000
1250 1500 750
Bandwidth
100KHz
400KHz
1800KHz
1200KHz
1
Instructions
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Table of Contents
Related Manuals for MFJ MFJ-1795
Summary of Contents for MFJ MFJ-1795
- Page 1 MFJ-1795 Vertical Antenna INTRODUCTION The MFJ-1795 HF antenna was designed to provide portable or permanent operation from restricted locations. When combined with the MFJ Ground-Coupled™ Portable Antenna Base or other suitable grounding system, such as radial system, the result is a small vertical antenna under 10 feet in height.
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Page 2: Antenna Height
INSTALLATION The MFJ-1795 was designed as a low profile, portable antenna. When combined with the MFJ Ground-Coupled™ Portable Antenna Base the antenna will provide permanent or portable communications. This is an ideal antenna for restricted locations. However, the antenna installation MUST be protected with non-metallic fencing to provide personal safety and to prevent antenna damage. -
Page 3: Tools And Time Required For Assembly
MFJ-1795 Vertical Antenna Instructions WARNING: If the antenna falls it will be damaged and may cause serious injury. Whatever type of installation you choose, remember that the antenna should be installed where it can never be contacted by people or animals. -
Page 4: Safety Precautions
MFJ-1795 Vertical Antenna Instructions [ ] Quality low-loss 50-Ohm coax with a PL-259 to go from the antenna to the transmitter. [ ] Either a SWR meter or Analyzer (MFJ-259, 269) SAFETY PRECAUTIONS: WARNING: You can be killed if the antenna, feedline, or the equipment used to install the antenna accidentally contacts any utility lines. - Page 5 MFJ-1795 Vertical Antenna Instructions [ ] Two 7/16" open end wrenches or one wrench and one nut driver for the U-bolts. [ ] Heavy Wire cutters for trimming capacitance spokes. [ ] Safety glasses. [ ] 4. Decide on the approximate height of the antenna. Maximum height will be just under 10 feet while minimum will be 6 1/2 feet.
- Page 6 MFJ-1795 Vertical Antenna Instructions [ ] 10. Place one of the hose clamps around the aluminum tubing and snug the clamp using a 5/16” nut driver . The center conductor of the coax will be connected to the antenna using a solder lug placed under the clamp.
- Page 7 [ ] 14. Double check the tightness of all the hardware you installed. Then, mount the antenna on the short temporary tuning mast or the MFJ Ground Coupled Portable Antenna Base. [ ] 15. Secure the mounting bracket to the fiberglass insulator as shown in Figure 5. Make sure the antenna mast does not contact the U-bolts.
- Page 8 The antenna base should be assembled using the instructions supplied with the unit. The following instructions will explain the installation of the MFJ-1795 to the antenna base. [ ] 1. The U-bolts should be attached to the base through the holes as indicated in Figure 5.
- Page 9 MFJ-1795 Vertical Antenna Instructions SO-239 Bushing U-bolts Anetnna Base Figure 6 [ ] 3. The plastic bushing supplied in the parts should be placed in the hole under the SO-239 connector. [ ] 4. Now the 15” piece of insulated wire should be passed through the plastic bushing to the antenna feed-point.
- Page 10 40 KHz) and is the most sensitive to adjustments. The entire antenna must be accessible during initial tuning and testing. If the MFJ Ground Coupled™ Portable Antenna Base is used, attach the antenna to the base and place it in a location away from buildings or other objects that could affect the measurements.
- Page 11 MFJ-1795 Vertical Antenna Instructions IMPORTANT: A suitable Ground radial system must be connected to the antenna mounting bracket if the Ground Coupled Portable™ Antenna Base is not used. The SWR can be measured by using a transmitter and SWR bridge or an SWR Analyzer. The measuring device should be connected to the antenna with a reasonably short length of high quality 50-Ohm coaxial cable.
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Page 12: Grounding Considerations
MFJ-1795 Vertical Antenna Instructions 20 M 1.1:1 at 13.5 MHz 15 M 1.2:1 at 18.72 MHz 10 M 1.4:1 at 23.6 MHz If the resonant frequency is lower than what your equipment detected, take one spoke off to raise the resonant frequency. Measure the resonant frequency and calculate the approximate resonant frequency as if the spoke was in place using the chart on the below. - Page 13 MFJ-1795 Vertical Antenna Instructions...
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Page 14: Maintenance
MFJ Technical Service at 662-323-0549 or the MFJ Factory at 662-323-5869. You will be best helped if you have your unit, manual and all information on your station handy so you can answer any questions the technicians may ask.