Spi-Ro traps

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W0CMO, May 20, 2019.

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  1. KM3D

    KM3D Ham Member QRZ Page

    I don't know the construction of the Spi-Ro traps, but traps made using COAXIAL CABLE for both the inductance and capacitance do have 'polarity'; the physical lengths of wire are different depending on the trap 'direction'. Both traps must be oriented the same way for balanced line lengths. Open your Spi-Ro traps at your own risk.

    I bought a pair of Spi-Ro LC-160 'antenna lengtheners' for 160 meters years ago. They are NOT traps, using only inductance to make the antenna physically shorter. I have used them off and on for years (not enough real estate for permanent deployment) and they do still work fine. The inductance is about 125 uH and the antenna is a 100' dipole (50' each leg) with the inductor in the center of each element, resonant on 1.850 MHz. Nowadays one could probably wind an inductor on a larger diameter PVC and have a little less loss (it looks like Spi-Ro used 1.5" pipe to enclose the coil). If you do this, use solid (not stranded) wire!

    Thanks to Spi-Ro I have been able to work on 160 meters with a decent signal.

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