Hi Stefan,
For a resonant design (tuned with parallel capacitor) I'd use the
litz wire. For the broadband design (terminated with a low-Z
amplifier) it shouldn't matter too much, but 0.5 mm wire diameter
would be the minimum. The thinner the wire, the larger the 'R', R is
noisy, and we don't want noise ;-)
7 rods in a bundle, and two of these bundles sound good. But it
depends on the material (permeability) if it makes sense to use 8
"parallel" rods - consider this: one single rod may already
'attract' enough magnetic field lines from the far field; 7 rods
will not attract 7 times as much ! Anyway for backpack operation you
don't have the choice to build a meter-long rod like Lubos' large
antenna.
Beware that my crossed-loop antenna was built for VLF, not LF.
Cheers,
Wolf .
Am 15.08.2011 19:26, schrieb Stefan Schäfer:
Hello Wolf,
Thanks to the link to your nice to read article. I just found it a
hour
before your mail and already read it ;-)
Well, i also prefer the usual configuration instead of that sleeve
antenna. Also i have to keep the focus on my actual goal: Making a
handy antenna for amateur LF / p operation without a car! And the
16
rods i will get (14 cm long, 8mm diameter) will be best in a 2x7
config. i think. Or do you rather suggest 3x5 or even 4x4?
2x7 is then about 30 cm long which is very fine for a backpack and
should be robust enough.
I would use the same double side bonding tape, this is very useful
to
get a first fixed arrangement. Then putting all that in a PVC
tube, 2mm
thickness and add the turns above the tube.
Would you recommend litz wire or standard 0.5 mm enamelled wire?
As an E field shield i would use aluminium bonding tape, without
making
a shutcut turn of course.
So the newcomers should not think that this antenna is the best
what
one can use for LF. Just in that special case of /p i see
advantages.
Otherwise a well designed loop (+ preamp or a very sensitive RX,
if a
samll loop is used) or E field antenna such as the PA0RDT should
be
preferred, as Alan already pointed out.
Looking forward to a direct comparison of the DCF39 SNR that can
be
achieved and to the first amateur signal received with that
antenna in
/p...
73, Stefan/DK7FC
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