The Voltage Probe Antenna
My own interest in these tiny antennas began in early 2013 and was prompted by the receiving antenna used on the University of Twente web SDR. The voltage probe antenna in question – a VPA or Active Antenna – is a design by PA0DRT and known colloquially as the PA0RDT MiniWhip. (Visit dl1dbc.net/SAQ/miniwhip.html and other pages for more information.)
It’s interesting to note that so many articles about VPAs generally are PhD theses, military references and commercial applications notes. The Active Antenna has a very poor showing in amateur radio circles. The benefits of using one have to be demonstrated to radio hams! Every presentation I’ve given to radio clubs on this topic has always included, somewhere in its first thirty seconds, words along these lines. “Tonight’s session is really a practical one and not – at all – a theoretical one.”
That’s generally a useful way to get the attention of those present but to keep it there has to be a practical demonstration as proof. Claims and testimonials from other users of these antennas is never enough. But, as well as making, using and enjoying the benefits of these devices it’s good to know how they work! I don’t run a web SDR so the best I can do for a demo is to direct you back to Twente and then introduce a real VPA project alongside some of the background.
Download a step-by-step builder’s guide from here