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
Am 15.08.2011 18:33, schrieb wolf_dl4yhf:
Hi Stefan,
The rods were found in Friedrichshafen for a bargain price. I later
discovered (most likely after the topic had been discussed here, or in
the VLF group) that these rods are used for inductive welding
(google("Ferrite Impeder Rod"). Here's a bundle of them:
http://www.qsl.net/dl4yhf/vlf_rdf/vlf_rdf_loop.html
They are 20 cm long.
The most effective use (to "catch the magnetic field from a distant
transmitter") is NOT to connect them 'parallel' in a bundle, but to
connect them in series (up to a certain point). This is much in
contrast to the esoteric sleeve thingy seen somewhere on the web.
73,
Wolf .
Am 14.08.2011 23:43, schrieb Stefan Schäfer:
Wolf,
Which dimensions has your ferrite rod had?
Never thought i will find a source for rods that are longer than 10 cm
but see: http://www.box73.de/catalog/product_info.php?products_id=1422&osCsid=rqlpfme957i65d7etjil1ntru5
even an official distributor..
Any better links?
73, Stefan/DK7FC
Am 14.08.2011 22:27, schrieb wolf_dl4yhf:
Ferrite RX antennas.. been there when 136 kHz started.
Not as good as a larger air-core loop, possibly noise caused by the
Barkhausen effect or similar effects, nonlinearities, etc.
Also beware the ferrite is a semiconductor so you will need some
E-field screening, otherwise the ferrite material will couple noise
into the windings. But it's not as bad as this may sound; actually I
used a ferrite antenna for reception for some years until I discovered
I had to disconnect the ...errr... RF counterpoise from the main
antenna from the mains "ground", and only use an earthstake during
receive, at DF0WD.
On the other hand, it's compact, relatively light-weight, and (in a
resonant configuration) gives a nice preselector.
I remember when I connected a ferrite antenna to a tiny receiver with
SA612 "gilbert cell mixer", the first signal I heard was G3KEV calling
cq in CW. Q5 in SSB bandwidth.
Such a receiver is extremely handy to go /p for reception, and compare
different sites.
73,
Wolf DL4YHF.
Am 14.08.2011 21:43, schrieb Minto Witteveen:
I haven’t thought about ferrite RX
antenna for LF….My guess is that it is not going to work – not without
an external antenna coupled to the ferrite, and then what’s the point?
DCF77 clocks often have trouble locking indoors or in the neighborhood
of ‘QRM’ generators like PC’s, and look what power DCF77 is using…
I could be entirely wrong of course…
73’ Minto pa3bca
Sent: Sunday, August 14, 2011 20:03
Subject: Re: LF: Re: 137 grabbers
<snip>
BTW what do you think about a ferrite RX antenna for LF? Now i'm
opening an older discussion i expect ;-)
73, Stefan/DK7FC
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