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Query: 70mhz.org
Links: 13 | Categories: 0
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The Four Metres website offer a global overview graph of the four meter band plans world wide -
This unit uses four capacitors, only two of which are variables, and a single tapped coil. It is built in a die-cast box, and has been tested up to 80W input power on 70MHz by G4CJZ -
Modification and verification of the FT847 to optimize 70 MHz performance by G4FUF -
This design has the following advantages low-cost components, Easy to set-up - nothing to adjust, no metalwork required, and only four soldered joints! -
This web article details the construction of a 4-meter band coaxial dipole antenna, designed for operation between **70.000 MHz and 70.500 MHz**. The resource provides a bill of materials and step-by-step assembly instructions for a half-wave dipole constructed from _RG-58_ coaxial cable. The design specifies a direct 50 ohm feedpoint impedance, eliminating the need for an external matching network. Construction photographs illustrate the stripping and soldering processes for the coaxial cable elements, ensuring proper electrical connection and physical integrity. The article includes specific dimensions for the radiating elements, derived from calculations for the 70 MHz band. The project outlines the physical dimensions required for resonance at 70 MHz, with the outer braid forming one half and the inner conductor forming the other. The feedline connection is directly to the coaxial dipole's center, maintaining a 50 ohm characteristic impedance. While the article does not present SWR plots or VNA sweeps, it focuses on the mechanical construction and dimensional accuracy for achieving a functional 4-meter dipole. The design is intended for fixed station use, with no specific mention of polarization or height above ground, but implies a standard horizontal orientation for dipole operation. DXZone Focus: Web Article | 4m Coaxial Dipole | Construction Guide | 50 ohm Feed -
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A Yagi-Mag antenna for the 4 meters band with NEC and MMANA files plans and pictures -
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A comparison of commercial 4m verticals by by Ian Hogan G6TGO -
A further study of the spurious emissions from an FT847 on 70 MHz by G7CNF -
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This PA has been designed by Sergey EX8MLE and uses three Mitsubishi RD100HHF1 FETs, Frequency Range 70 to 72 MHz