Re: Inexpensive source of ferrite for FSL not recommended for an LF FSL


graham.maynard1
 

Hi Steve,

Just came across this.
http://www.cosmoferrites.com/product/matcomp.html

Kevin e-mailed yesterday, and I forwarded the .pdf file for the ferrite rods I am using, and upon which my writing is based - A2 Nickel/Zinc.

From the above chart I wonder if the initial permeability of my rods is circa 10,000. I feel that using these in a sleeve much better preserves useful permeability when compared to when used as a rod, or, in rod like multiples.

Last year I wrote about modding the antenna in my Tecsun PL-380.
The rods in my sleeves are the same as the rod I used for that !
They make the Tecsun perform almost as well as my Sangean does with its 8" rod !

I was tidying out my greenhouse yesterday when I realised that flower-pot saucers would make brilliant FS Loop formers. They have edge lips capable of aligning and holding rod ends in place, and come in a whole variety of diameters.

Maybe what is not apparent from looking at the FS Loop on its own - though it has always been stated right at the beginning of my written text as uploaded in the FS Loop file - is that the FS Loop was merely a bi-product proof of ferrite sleeve inductor quality.

I was optimising the ferrite sleeve inductor for another (Tesla based)purpose, NOT as a receiving loop, and this is why Chris Trask's comments here and via e-mail directly to me were not only so offensive to anyone who holds dear to Truth, but so totally off target when he accused me of copying Polydoroff's prior work, of which I knew nothing about!

My text IS heavy reading, and this is because it deliberately relates to 'hands-on' findings which current theory cannot explain. It also never ceases to amaze me how people contact me because they think I do not understand 'their' theory, but which I avoid because it *closes down essential thought processes*, and starts futile arguments and bad (often aggresively egocentric) feelings, which are an exact opposite of the free sharing we all need for progress and the sharing I witness in this group.

I have thus added two dated paragraphs for 14th and 16th March to the end of my writing, and invite memebers to read these.
Right at the end of the text is a 14th March dated postscript.

Also in final notes No 9, is a 16th March addition related to the real reason for my sleeve investigations, and my need to understand what happens within the primary electron orbit (magnetic) domains of ferrite. I feel it very important that everyone reads this 'final note' because really it is only a part of the beginning of something much more important, and provides a link to more recent like minded work I did not now existed and thus was unaware of whilst writing.

http://www.gmweb2.net/The%20FS%20Loop.htm

Cheers .......... Graham.

--- In ultralightdx@..., "Steve Ratzlaff" <steveratz@...> wrote:

I received the shipment of ferrite today and made an LF FSL with them and
tested it. It is quite a bit inferior to other FSLs I've built--I really
can't recommend it, unfortunately. It might work OK for a MW FSL but I
haven't built any MW FSLs yet and don't have anything to compare one to.
If you're still interested, a major US distributor, www.digikey.com, carries
this ferrite that looked promising, classed as small ferrite used for EMI
reduction on ribbon cable. The specific Digi Key part number is P11388--just
enter that in the search engine on their home page and it will take you to
the item. Each piece is around 35 cents in quantity of 50 or more up to 100
pieces where it's 30.5 cents each. The ferrite is about 1.3" long x 0.39"
wide x about 0.25" thick. To use it as a ferrite "bar", you would butt the
0.39" sections together around the form, and wind the coil on the 1.3"
section.
I used a standard 4" sytrene coupler as a form, which is obtainable in the
plumbing section of stores like Home Depot. It has an outer diameter of
4.5". 37 bars fit around it almost perfectly, with just a small space left
over. Two wraps of 1/8" foam were used to give a 1/4" spacing of the coil
from the ferrite. Previous tests have shown that 1/4" to 3/8" spacing of
coil from ferrite is needed otherwise FSL output drops.
I would a 60-turn closewound coil using 40/44 Litz over the full 1.3"
ferrite length, this gave 1118 microhenries. With the recommended dual 338
pF polyvaricon tuning capacitor, this would tune to about 183 kHz at the
lowest frequency, which would cover the full NDB band but not all of the
LWBC band.
I have a FSL test setup I've developed very recently where I can measure the
output of a FSL and compare one FSL to another. Of the several FSLs I've
built so far, the original 40-rod one gives the highest output--that's also
the one I've been using to do ULR NDB DXing. I firmly believe that the FSL
with the highest output is also the most sensitive, and thus the most
desirable.
I will show what the 40-rod ferrite FSL measured on the FSL test setup and
what the new EMI ribbon cable ferrite FSL gave, then discuss what the
numbers mean.

40-rod FSL
450 kHz -74 dBm
350 kHz -74 dBm
250 kHz -74 dBm

EMI FSL
450 kHz -76 dBm
350 kHz -78 dBm
250 kHz -81 dBm

Unless you have worked in electronics it's unlikely you have any idea what
the numbers after the frequency mean. "dBm" is an abbreviation for "decibels
referred to one milliwatt, measured in a 50 ohm system". More positive
numbers (toward zero) indicate a higher output from the FSL (in this case).
Thus -74 is a higher output than -76 or -81. Decibels are a logarithmic type
notation--the greater the difference the greater the change in power, or in
terms of a radio signal, a -3 decibel (dB) difference means the signal is
half as strong compared to a signal at 0 dB. Each 3 dB halves that signal
power again. A one decibel change is the smallest change that you can hear
with your ears, if comparing sound levels. For a radio signal, when it's
converted to sound in the radio, that still applies, so the RF signal
difference of 1 dB is the smallest change in audio level you would notice if
you listened very carefully. Thus, the 40-rod FSL and the EMI FSL are about
equal at the high end, 450 kHz, but then the gap steadily widens as the
frequency is lowered. You would definitely be missing the weaker signals
down at 250 kHz, compared to the 40-rod FSL at 250 kHz.
If the differences between the two antennas were only several dB then I
would still recommend the EMI ferrite, but not with the large differences
noted as frequency decreases.
As mentioned before, perhaps this ferrite is suitable for MW use in a FSL,
but I don't know.
So it appears this fairly inexpensive ferrite is not suitable for use for an
LF FSL, unfortunately.
On eBay, searching "ferrite rods" still turns up some Russian sellers with
ferrite that has been tested and found to work very well in FSL, both
ferrite rods and ferrite bars. If you don't mind paying considerably more,
the US distributor Amidon also sells ferrite rods. The -33 type would be the
ones to choose to make LF FSL; the -61 type to make MW FSLs, though either
type would work for either LF or MW, though -61 might not have enough space
to wind a coil with enough inductance to work at LF. Amidon's URL for
ferrite rods is https://www.amidoncorp.com/categories/6
Gary DeBock uses Amidon rods for both his MW and LF ULR antennas he builds.
73,
Steve

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