Hallo group!
I'm testing an E-field antenna, like MiniWhip, but DC coupled for RadioNature
use, down to few hundred's Hz,
and up to VHF.
I've found that I have a lot of noise reduction if the antenna power supply is
a dedicated one,
with good shielding and decoupling, a 0.1 uF polyester capacitor in parallel of
the power transformer,
to smooth diodes transitories, and primary/secondary separated (dualC-core)
transformer.
The power supply have it's own ground.
Also using a separated power supply wiring vs signal wiring help.
I'm using a shielded cat5 computer network cable with 4 twisted pair.
One pair for power supply and another pair for signal; the signal pair go to
my receiver through an 1:1 insulation transformer. The shield is grounded only
at Rx side. This cable work well for LF, each pair have about 100 ohm impedance
and I think that at low frequencies twisted shielded pairs are less prone to
pickup noise
than coax cables.
But it's useful to test with other grounding and coupling configurations, noise
follow strange
paths I can't forecast ;-)
In the schematic L100 is a common mode choke, bifilar wound on 100 mm
ferrite rod or hi mu toroid.
The antenna work well also if connected to mike input of the audio board
through an 1:5 step-up
transformer, for RadioNature signals and SAQ.
The whip can be a 33 cl bear can or something like, not bigger.
I hope the schematic pass the reflector length filter.
73 de Claudio, ik2pii
--
Claudio Pozzi - Happy Linux User - http://www.qsl.net/ik2pii
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