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Old January 19th 08, 05:19 AM posted to rec.radio.amateur.homebrew
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First recorded activity by RadioBanter: Jul 2006
Posts: 271
Default Ferrite loop antenna for LW/MW band

Thanks Harold...........I whill give it a whirl. For the past few days, I
have been experimenting with the ferrite loopstick. Either winding works ok
(LW or MW), but if the LW winding is connected, it appears to cause some
self resonance problems with the MW winding in the middle of the band,
unless I ground both ends of the LW winding. Right now, I am trying a
multi-layer winding for the LW section to see if I can eliminate the
interraction. It should work..........my Grundig Satellit 3400 appears to
use this principle, unless there is a seperate pickup winding for each band.
Oh, about the call..............don't worry about it. I had to go to the
doctor myself today. Must keep appointments!

Pete

"Harold E. Johnson" wrote in message
news:UqMjj.39622$Ux2.21213@attbi_s22...
Is there any kind of program that makes the calculations a bit easier?
If I knew how to do the calculations, I could throw the formula into a
spreadsheet. What I need to do is calculate the inductance with the
parameters of cross sectional area, length, position on the ferrite rod,
number of turns, and permeability of the ferrite material itself.
I would like to throw these parameters into the spreadsheet/program, and
let the software calculate the inductance for me.

Pete


GM Pete. Sorry I had to be short on the telephone call, I had a doctors
appointment and was running late already. WRT your "antenna problem or
opportunity". I made an antenna for WWVB, and also use it for NAA at 24
KHz by adding an additional cap across it for resonance down there. It's
better heads and shoulders than any ferrite antenna I ever made. 24 inch
bicycle wheel, spokes removed and a space made in the wheel continuity by
sawing it apart and adding a small block of wood. This also serves to hold
an old ARCO tuning cap of high value, and an instrumentation amplifier
made from three LM833 op amps.

A layer of shipping plastic foam between the rim and 120 turns of HPT wire
(#26 is a good number), then wrap it all up with a bit of squeezed on
aluminum wrap. (Also not continuous, and grounded at the spacer.)

With the inst, amp set for 60 dB of gain, I receive WWVB at about -40 dBm
into the 50 Ohm input to a HP selective Voltmeter. Best ever ferrite was
around 30 dB worse than this. I use it almost continuously for NAA
monitoring of SIDs, and they never go out of detection even in the
basement workshop.

Regards and happy New Year.
W4ZCB





 
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