G3TSO Homebrew

by Peter Asquith, G4ENA

	There has been much exposure in the Amateur Radio press concerning the new 'Miracle Antenna', produced in Canada for use with low power transceivers. Being capable of continuous tuning from 80m to 70cm, it offers fantastic flexibility for the /P, QRP enthusiast. This article describes, not the low cost version, but the NO cost version of this product. I present the reclaiM Antenna. A dive into the junk box produced all the necessary components for this project. The primary area of concern was how to achieve the wiping contact on the auto transformer. The raw material for this came from an ancient Colvern potentiometer. Removal of the back and slide wire created the housing for the ferrite ring. It was also necessary to remove some of the plastic inside to make space for the wound core.
	Auto transformer Winding the core was probably the most demanding and skilful part. A thin strip of double sided adhesive helped hold each of the turns in place as in excess of 60 turns of 0.4mm wire were wound on making sure each one was evenly spaced to the last.
	On completion a small amount of super glue applied to the inner and outer edge of the core secured the turns. This permitted removal of the insulation with a scalpel. Three blobs of hot melt glue hold the transformer in place. Wiping Contact. A circlip retains the pot' shaft in the housing. Removal of this component permits the necessary modifications to the wipers. Only one is required to contact the transformer. The very tip of the wiper had a small indent filed in it to provide a positive feel for position. Existing terminations in the housing gave convenient connections for the transformer and wiper. It was necessary to secure both ends of the flexible wire from the wiper, using hot melt glue, to prevent fatigue during use to the soldered joints. To achieve a smooth running action it was necessary to apply a small amount of lubrication to the windings.
	Enclosure The junk box yielded a two part plastic box, ideal for this project. Fitting of the whip aerial, auto-transformer and PL259 plug was straightforward. An additional spring loaded connector for wire aerials was added for greater field flexibility. Does it work? Well, yes. Since the ferrite ring from the junk box was not of the right type, as specified in the original QST article, the LF end is a bit compromised. If the correct spec' part is fitted, then there is no reason why it should not perform like the real thing.