New enclusures

John W Cress <jwcress2@...>

Chris, I'm planning to use my recently aquired loop outside with a large coax based shielded loop. I'm also planning to remount both PCB's in cast aluminum enclosures which are both just large enough for the boards. Do you see any problems with the metal enclosures affecting the tuning? My interest is primarily with 60Khz WWVB, to the extent that if it works well at 60Khz I have no concerns about the remainder of the spectrum.

John K0GCJ

Chris Moulding

If you are using a shielded loop then the Loop Antenna Amplifier head unit PCB can be mounted in a shielded metal enclosure. The head unit has two separate grounds separated by a common mode filter. Without running some tests I'm not sure which ground to connect to the metal enclosure so try running a wire from the box to either ground plane on the board to find which one is most effective at reducing noise with your shielded loop. I suspect that the enclosure to the ground plane on the loop rather than the coax input will give best results.

The base unit can also be mounted in a metal enclosure. Connect a wire from the ground on the board (USB shield) to the metal box. You can also connect the metal enclosure on the base unit to ground to reduce noise and conduct any static electricity on the antenna to ground.

A shielded loop will work well at 60 kHz. The problems with them occur at higher HF frequencies where the loop inductance and capacitance to the shield form a resonant circuit.