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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