Re: LF: Results of optimising an active antenna

[Gary - G4WGT <g4wgt@tiscali.co.uk>]

Alberto, LF,

I tried that arrangement with my PA0RDT Mini-Whip active antenna inside a large baked beans can, the can being the antenna & the results were a lot poorer than the small 30mm x 45mm of the original design, I have also tried adding a 500mm whip to the original with poorer results also. So now I use the Mini-Whip as originally designed by Roelof. You can see the results on my grabbers.

http://myweb.tiscali.co.uk/wgtaylor/grabber2.html

73

Gary - G4WGT.

2009/12/2 Alberto di Bene <dibene@usa.net>

Stefan Schäfer wrote:

My Conclusion: It seems that a short receiving antenna can bee seen as a capacitive divider out of the capacity between far field and antenna and the capacity between antenna and ground. If the wire length is to much, the input stage becomes nonlinear/goes into saturation. If the height above ground is increased the signal comes up, but not the signal/noise ratio(surely there will be a benefit if such an antenna is placed in a region with heavy local qrm. Then, the height should be increased and the wire length can be decreased). So, one cannot say “the more the better” talking about the wire length!

It would be quite interesting if somebody could try to use, instead of a wire, something
with a greater capacity towards ground, e.g. a can of beer (after drinking the beer, of course...:-)
One of half liter (slightly more than 1 pint) could do, I think...

Maybe the increased capacity towards ground could make it more effective than a wire

73  Alberto  I2PHD

P.S. And the entire active antenna circuitry could be placed inside the can...