Stefan Schäfer pisze:
Jim, LF,
I'll try to go on as fast as the distributor and ebay did ;-) So this
is the current situation:
Decided to use the 2x7 bundle. The cross section area of 7 pcs. just
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
intentionally broke one rod and put the 2 halfs to the inner ends. One
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
way into the bundle of others packed hexagonaly
in a first instant i've asked myself what is the reason Stefan is making
a mini-device
for slowing down fast neutrons..... ;)
Stefan, you have a "nasty" habit of triggering various activities of
almost all members of this reflector.. :)
You already have created a 8.97 kHz saga and now we start to play
with ferrite antenna. - of course, i , too, got infected...
Back to 70's and 80's the basic QRO army equipment in some countries
was the R-140 TRX station. Its TX pwr was well above 1 kW in the range
1.5 - 30 MHz.
On the receiving side , among different wire antenas, the R-140 setup
had so called "ferrite receiving antenna" ( polish abbrev. FAO) for
RX'ing ground wave comms
within the range 1.5 - 12 MHz. Some time ago i managed to get this
FAO antenna on one of domestic auctions.
it has two very big ferrite rods - see:
http://obrazki.elektroda.pl/3964686700_1292246389.jpg
one such a ferrite rod is 450 mm long and its diameter is 40 mm. (
these numbers are refered to the external housing of the ferrite material)
i put 64 turns of wire on this rod - it comes out with 714 microHenr of
inductance so approximately 2nF cap resonates this antenna in 137 khz
region.
It was parallel LC combination so i took BF245 FET as buffer and
BC109C as an amplifier. i put this very ugly/shaky construction down
on the floor,
2 meters from the balcony window. On tthe balcony i have 1
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
( 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
slightly better than loop placed outside.
ferrite: http://www.toya.net.pl/~mlynarski/fer.jpg
loop: http://www.toya.net.pl/~mlynarski/loo.jpg
yours, Piotr, sq7mpj
qth: Lodz/jo91rs/
p.s. still have some time off so i will continue...
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