LF: Re: MiniWhip antenna, fiber optic

[Stefan Schäfer <Stefan.Schaefer@iup.uni-heidelberg.de>]

another image of the TX: https://dl.dropboxusercontent.com/u/19882028/LF/DK7FC_fiber%20optic%20active%20dipole_TX2.jpg

Am 08.07.2013 01:59, schrieb Stefan Schäfer:

Hi all,

OK, although it can't work (do you remember?!) i built an active antenna with battery supply and fiber optic output. The active part is a BF862. The circuit is quite simple: https://dl.dropboxusercontent.com/u/19882028/LF/DK7FC_fiber%20optic%20active%20dipole%20schematic.jpg It is a first idea for the schematic. Maybe i will change it later so that the gate is shifted to 9V/2. Just for first experiments. In various tests with the BF862 i found that it was necessary to add a ferrite bead directly in front of the gate to prevent VHF oscillations of the JFET.

The TX is already working: https://dl.dropboxusercontent.com/u/19882028/LF/DK7FC_fiber%20optic%20active%20dipole_TX.jpg
Yes yes yes, it is not truely symmetric and the capacity at source must be a bit larger than that of the leg connected to gate. Anyway it will be useful for some basic and interesting experiments.

RX is ready tomorrow.

73, Stefan/DK7FC