Magnetic Loop antennas or STL (Small Transmitting Loop) antennas are one of the best kept secrets in antenna physics. Magnetic Loops are usually very small, typically much smaller than 1/4 of a wavelength in circumference, yet they can radiate a potent signal that would rival that of a full sized dipole. In the above video, I demonstrate how well these antenna work. It took my son Noah and I less than 2 hours to design and fabricate this antenna. Our first contact was to a station on the West Coast.
When home brewing communication antennas, and in my case magnetic loop antennas, one needs an effective way of feeding the antenna. I struggled with zero success to find a supplier of SO-239 connectors suitable for antenna construction. I needed a strong mechanical as well as electrical connection to a gamma matching rod. In the above video, I show and explain how using a metal lathe, some aluminum round bar stock and UHMW plastic I was able to construct a robust SO-239 to 1/4 threaded rod for use in my magnetic loop design.
One of the great aspects of the amateur radio hobby is learning information beyond electronic theory. I have come to really appreciate how Space Weather and subsequent Atmospheric conditions can affect radio communications. Things like the sun ejecting a CME (Coronal Mass Ejection) can create auroras and other ionospheric conditions which are conducive to providing great and sometimes not so great conditions. In the above example, I used a low power QRP transmitter in the VHF 6 meter band to reach a fellow ham radio operator hundreds of miles away. My MFJ-9406 transceiver RF power output was less than 10 watts.
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Portable QRP, or low power amateur radio communications is becoming very popular since the introduction of the Yaesu FT-871ND and Icom IC-703 radios. New compact field/trail radios such as the Ten-Tec R40Series, Elecraft KX1 and others are making this hobby very exciting for those wishing to operate portable and/or QRP. The introduction of limited space, quick deploy antennas for HF low band operation, along new technology long life batteries have made portable radio operation not only possible, but very effective and enjoyable to both the ham radio enthusiast and emergency response field personnel alike.
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