Message-ID: <4E4DBB6B.8080208@toya.net.pl>
Date: Fri, 19 Aug 2011 03:24:59 +0200
From: Piotr Mlynarski <sq7mpj@toya.net.pl>
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Subject: Re: LF: Ferrite RX antennas
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Stefan Sch=C3=A4fer pisze:
> Jim, LF,
>
> I'll try to go on as fast as the distributor and ebay did ;-) So this=20
> is the current situation:
>
> Decided to use the 2x7 bundle. The cross section area of 7 pcs. just=20
> lokks better :-) Also the complete stick is much more handy and robust.
>
> Markus/DF6NM gave me the hint to overlap the inner rod by 50%. So i=20
> intentionally broke one rod and put the 2 halfs to the inner ends. One=20
> complete one is now in the inner center.
>
> See: http://dl.dropbox.com/u/19882028/LF/ferrite%20antenna%20parts.JPG
>

Dear Stefan,  LF Group,

when i saw the above picture with one of the ferrite rods inserted half=20
way into the bundle of others  packed hexagonaly
in a first instant i've asked myself what is the reason Stefan is making=20
a mini-device
for slowing down fast neutrons.....   ;) =20

Stefan,  you have a "nasty" habit of triggering various activities of=20
almost all members of this reflector..  :)
You already  have created  a 8.97 kHz  saga  and  now  we start to play=20
with ferrite antenna. -  of course,  i , too, got  infected...

Back to 70's and 80's   the  basic QRO  army equipment in some countries=20
was the R-140 TRX  station. Its TX pwr was well above 1 kW in the range=20
1.5 - 30 MHz.
On the receiving side , among different wire antenas,  the R-140 setup=20
had so called "ferrite receiving antenna" ( polish abbrev.  FAO) for=20
RX'ing  ground wave  comms
 within  the range 1.5 - 12 MHz. Some time ago i managed to get this=20
FAO  antenna on one of domestic auctions.
it has two very big ferrite rods  - see:   =20
http://obrazki.elektroda.pl/3964686700_1292246389.jpg
one such a  ferrite rod is 450 mm  long and its diameter is 40 mm. (=20
these numbers are refered to  the external housing of the ferrite materia=
l)
i put 64 turns of wire on this rod - it comes out with 714 microHenr of=20
inductance so approximately 2nF cap resonates this antenna in 137 khz=20
region.
 It was parallel LC combination so i took  BF245 FET as buffer and=20
BC109C as an amplifier.  i put this very ugly/shaky  construction down=20
on the floor,
   2 meters from  the  balcony window.  On tthe balcony  i have  1 =20
square meter loop with 11 turns and  OP27
( see:  http://ik4hdq.net/doc/testi/smlloop.pdf  )

Loop and the ferrite antenna were oriented towards JO52WG  grid-location=20
( dcf39).  i have used SDR-IQ with 9 khz span with 137.5 set as mid freq.
The ferrite antena ( placed in the middle of the room ! ) performed=20
slightly better than loop placed outside.
ferrite: http://www.toya.net.pl/~mlynarski/fer.jpg
loop:   http://www.toya.net.pl/~mlynarski/loo.jpg
                                                                         =
         =20

                                                                         =
                            =20
yours, Piotr, sq7mpj
qth: Lodz/jo91rs/

p.s.  still have some time off so i will continue...