GW4ALG's QRP Radio Pages

[ GW4ALG went QRT in February 2007 ]

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Delta Loop Antenna

This antenna was in use at GW4ALG between March 1998 and May 2002. 

When I started operating on 136 kHz in 1998, I needed an antenna that could be resonated easily for this LF band.  So I modified my pre-existing 'inverted V' doublet to form a top-fed delta loop having an overall perimeter of about 65 m.  The base was about 1.7 m above ground level (AGL), and the apex was about 10 m AGL.  This resulted in an effective magnetic loop antenna for 136 kHz, as well as providing a general purpose antenna for 10 - 80 m.

Indeed, this antenna proved to be surprisingly effective on 3.5 MHz (as a large loop).   It gave reasonable performance on 10-30 m; but poor performance on 40 m.

 

loop.bmp (17086 bytes)

 

At the shack end, the delta loop was tuned using a Z match ATU for all bands 10 - 40 m.  As luck would have it, the antenna was a perfect match on 80m (when using a 1:1 balun) - so no ATU was required!

I abandoned 136 kHz when the first RSGB repeater arrived (October 2001), and, in May 2002, the antenna was restored to an 'inverted V' doublet having G5RV dimensions.