Some research on the internet brought up a design by PA0RDT (pls search for it yourself). He call's the thing "mini whip". Some would call it an EH-antenne (haha, got you there), some others would call it an amplified E-probe. The latter it actually is. It is a capacitor probing the E-component of an RF-field.
However the design may be called, is it any good?
First to mention, there are many positive reports on this device. I had my doubts, but never the less, on a yacht, aerials are a compromise whatever one does. Thus, in particular inspired by the positive feedback found, I decided to give it a chance.
The key to the amplifier-circuit seems to be the 1MOhm resistor input network. I figure, 10MOhms would propably do a better job. However, not having 10MOhms-resistor in my stock, I went for 1MOhms. Which reduced my stock that much, that the next thing I'll do will be visiting my electronica-boer in order to buy said resistors.
Here comes the modification, unvoluntary, sort of... even though a 2N5109 seems widely available, it was not in my stock... I decided to replace it with a 2N918; this required to change the emitter-resistor to something higher-ohmic, in order to reduce Ic. I went for a conservative 470 Ohms. As for the DC-separating inductor, I went for what I found (whatever it was).
And this is, what I ended up with:
The result was pretty nice, although I tested indoors only. I am curious what this probe could do, when "flying" meters above my house's roof...
Should I ever build another one, that's what I would change:
- use a 2N5109 (will propably give better results... or not)
- increase the "ground-plane" part of the probe by reducing the "12V-part"
Conclusion: The probe will have to prove itself, when hoist to the top of my ship's mast. Presently it appears to be a nice alternative to something more vulnerable, since, rugged it is!
