BBC
About the article

Wideband active loop antenna

for general-coverage receivers

Wideband active loop antenna
There’s nothing better than a long-wire antenna for shortwave reception, but not everyone has the necessary space. The active loop antenna described in this article can be an excellent alternative to a long-wire antenna where space is restricted. Not only is it easy to build, it also provides outstanding performance and is very inexpensive.Anyone who wants to use a general coverage receiver for more than just listening to the BBC World Service or the Voice of America (VOA), soon discovers that a simple telescopic antenna has its limitations. The efficiency of such an antenna is very low, and it also picks up a lot of interference when used indoors. If you take long-distance short-wave reception a bit more seriously, you will soon find that you need something better.What then should it be? Whole books have been written about antenna technology, and there are countless types and varieties of antennas. Before plunging into the forest of possibilities, it’s a good idea to first consider what requirements the antenna in question should meet.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor Members can exclusively download these files for free as part of their Membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service. Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Resistors:
R1,R2 = 82k?
R3 = 560?
R4 = 220?
Capacitors:
C1,C2 = 2nF2 ceramic, raster 5mm
C3 = 100nF ceramic, raster 5mm
C4 = 100nF, raster 5mm or 7.5mm
Semiconductors:
T1,T3 = BF494
T2 = BF451 (BF450)
Miscellaneous:
K1 = BNC or cinch socket
10 to 15 metres enamelled copper or hook-up wire
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