HFU HF Underground
Technical Topics => Equipment => Topic started by: Corvus on November 13, 2017, 0418 UTC
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I recently reproduced a design by PA3GZK that is also described by PI4NOV. Has anyone else built one of these?
The copper for the loop and fittings is fairly expensive and its partially SMD, so be prepared for tiny soldering on small boards. I had to add a SMD low pass filter to the preamp input to suppress FM broadcast images, there aren't any close by AM transmitters so that wasn't a problem but I suspect close by transmitters would be. My finished copy about 5 meters above ground works so well across the LW/MW/HF band it's just shocking, it consistently out performs a 115' long wire and a wideband vertical by a wide margin.
Wasn't really easy and it took a while, but it was oh so worth it.
PA3GZK design:
https://pa0fri.home.xs4all.nl/Ant/Active%20antenna/Active%20receiving%20%20loop%20antenna%20eng.htm
PI4NOV (in Dutch):
http://arjan-broekhuizen.wixsite.com/pi4nov/loop-antenne-voor-ontvangst
Low Pass Filter:
http://homepage.eircom.net/~ei9gq/lpf.html
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I've never built a shielded magnetic loop, but have been meaning to give it a try. I'm tempted to build two loops of that design and use them with my LZ1AQ amplifier, which presently has two aluminum foil wrapped hula hoops as the antennas. Thanks for sharing the links.