Loop Antenna Splice Reinforcement

Those solder joints and finicky little wires seem much too fragile on their own:

LF Loop Antenna - complete joint

LF Loop Antenna – complete joint

This should help:

Loop Antenna Splice - assembled

Loop Antenna Splice – assembled

Foam blocks hold the ribbon cable in place and provide a bit of strain relief around the hard plastic edge:

Loop Antenna Splice - hardware

Loop Antenna Splice – hardware

The brass inserts in the bottom block (on the left) got epoxied in place, because they must provide quite a bit of force to clamp the foam. Their larger knurled end sits flush with the outside surface and the smaller end has one thread thickness of clearance below the inner surface.

A last look at the wiring:

Loop Antenna Splice - wiring

Loop Antenna Splice – wiring

I think the preamp must sit at some distance from the antenna to prevent feedback, but that remains to be seen.

The M2’s nozzle accumulated a huge blob of PETG that turned into a giant smear:

Loop Antenna Splice - PETG booger

Loop Antenna Splice – PETG booger

Fortunately, it’s on the inside where nobody will ever see it. If you know where to look, it’s barely visible from the outside.

The solid model shows off the structure a bit better:

Loop Antenna Splice - show view

Loop Antenna Splice – show view

The inside view:

Loop Antenna Splice - bottom

Loop Antenna Splice – bottom

The OpenSCAD source code as a GitHub Gist:


, ,

  1. #1 by madbodger on 2016-12-27 - 09:15

    That looks a lot better from both æsthetic and engineering viewpoints. If the epoxy fails to hold the brass inserts in place, you could replace them with tee nuts, I suppose. You could even add grooves for the prongs in the 3D model (I’m not sure how well they’d dig their own grooves in PETG) and a depression for the flange if you want it flush.

    • #2 by Ed on 2016-12-27 - 09:36

      “Æsthetic”. Now, that’s a word last seen slinking around under the workbench, with a hunted look in its vowels. Rounded corners seem as close as it’ll get to the light… [grin]

      Ramming inserts into slightly undersized holes usually suffices, heat-staking requires too much precision + fiddling, and epoxy gets the job done. I am mightily pleased with knurled inserts and wish I’d known of them much earlier!

  1. 60 kHz Preamp: Board Holder | The Smell of Molten Projects in the Morning