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published: Sunday 24 April 2016
modified: Sunday 24 April 2016
author: Hales
markup: textile

Selectable turns AM loop antenna

I've made a couple of AM loop antennas before, but I have never been sure of how many turns to wind and the results (when connected to my radio) have been lacklustre. Today's job was to make another but with a variable number of turns.

Construction

I started by cutting and marking out a sheet of plywood to mount and wind the antenna on. The circle was made using a stick with two holes, a nail and a pencil. The other lines were for centre and square-line finding:

I drilled out 16 holes around the perimeter of the circle and hammered in wooden pegs. Despite the saying, square pegs do fit into round holes (nice and snugly):

Nothing fancy on the backside:

I then struck ten nails in at the bottom of the loop and used these as taps for my windings. I wound each loop of the antenna with a seperate piece of wire and terminated each end on the nail farm:

In the picture above you can also see a few other features:

Results

It works wonderfully! Different parts of the AM band work better with a different number of turns selected on the antenna. At certain ranges I found that 7 turns picked up something nasty that sounded (by ear) a good 10 or 20 more dB louder than everything else. At other ranges it provided the loudest/clearest.

Misc details


Jim Morrison - Wednesday 29 August 2018

I have been searching the net for just this kind of thing, but i have been searching "tapped loop" antennas. A guy on YouTube did a tapped loop around a milk crate. Then this finally showed up. It makes total sense to me but you just don't find it! Good for you! I am just about to wind a 4 foot square loop. The frame is done and the winding starts tomorrow. It will now be tapped. Thank You.

Hales - (site author) - Sunday 2 September 2018

Thanks Jim. As I briefly mentioned above: I have tried making AM loop antennas before, but they've always been garbage, even when I've followed people's advice on how many turns to use. Antenna impedance and matching are too complex of a problem to attack without more expensive gear -- I think tapping turns and listening 'by ear' are much better solutions for receivers.


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