Diamond-SG-7900

sg7900.jpg

SG7900: 144/430MHz(2m/70cm) Warning this is probably not a genuine Diamond Antenna

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Tuning

Ths is sold as a pre-tuned antenna at 144 and 430 Mhk.

A minor VSWR adjustment can be useful, which can be done by moving the antenna up/down at the base end.

The top of the antenna to the start of the coil as your vhf element and the two short elements as your uhf elements, stacked 1/4 PD half have with a coil that breaks the rf pattern.

I'd start with removing the original elements first and replace it with a single whip element. Get a noise bridge or antenna analyzer and find your new resonant frequency of the antenna. You will discover if the bottom has a network or coil that tunes the original antenna. Prune and Tune. When you getting close on vhf, try uhf. See if there is a relationship.

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Glenn Lyons VK4PK
glenn@LyonsComputer.com.au
Ver:gnl20200724 - pre published v0.9