Re: Inexpensive source of ferrite for LF FSL

Gary DeBock

Hello Joachim,

Thanks for sharing the results of your first FSL project with us.

Steve and Kevin may have their own comments, but I'll suggest a couple
of tips. For covering the NDB band with an inductively-coupled FSL,
1615 uh may be a little high for coil inductance. 1615 uh is close to
the inductance normally used for a directly-connected LW loopstick
coil, and your FSL's variable capacitor would extend the FSL's longwave
frequency coverage even lower. With your current components, you
probably should be able to cover the entire NDB band with about 1000 uh
of coil inductance.

The only operating suggestion that I could make (after viewing your
photos) is to ensure that the FSL is parallel to the table when you are
using it (and not standing on one end, like in your last photo with
ther variable cap connected). Any FSL standing on one end will not
receive much of anything, although the tuning noise will be there (as
you describe).

73 and Good Luck,
Gary DeBock (in Puyallup, WA, USA)

-----Original Message-----
From: rabej_de <rabej_de@...>
To: ultralightdx <ultralightdx@...>
Sent: Sun, Mar 27, 2011 11:58 am
Subject: [ultralightdx] Re: Inexpensive source of ferrite for LF FSL

Hi, list!

Yesterday I built my first FSL using a 150 mm dia. Styrofoam former, 23
ferrite bars, 100x20x3, permeability 400, 3 layers of bubble wrap and
55 turns of 100/44 litz wire = 1615 uH.
I connected it to a 3-section 12 - 460 pF var. cap. with 2 sections in
Pictures of it can be found here :

I only had time to do some qick in-shack tests using my Tecsun PL-380
and I must admit that I am a bit disappointed.
Yes, the noise level increases when the FSL is tuned exactly but I was
not able to hear more NDBs than without the FSL.
Maybe this is due to the high noise level indoors with PCs and TVs
running etc. - I have to check that.

Any other advise or hint as to what may have gone wrong?


Joachim Rabe

--- In ultralightdx@..., "rabej_de" <rabej_de@...>

Hi, list!

Found these ferrite rods on eBay :;item=400137000838&fromMakeTrack=true&ssPageName=VIP:watchlink:top:en

They measure 8 x 125 and are said to be 400 permeability.

Ony comments on using them for a LF-FLS?

Thanks very much in advance.
&gt; 73s

Joachim Rabe

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