Re: Ferrite Sleeve Loop Antenna Testing


Thanks for the MP3's Gary. Now we can hear what you've been talking about.


--- In ultralightdx@..., D1028Gary@... wrote:

Hello All,

Continuing the experimentation already started by Steve and Kevin, I
decided to construct my own version of Graham Maynard's Ferrite Sleeve
Loop antenna. Although there has already been a lot of discussion of
this new antenna design here in the Ultralightdx group, the emphasis
seems to have been on the technical details, and not on the practical
DXing applications of the high-gain antenna.

One of the challenges facing a DXer desiring to construct an FSL
antenna is the cost of the ferrite rods, which can be considerable. The
most effective FSL models have a very large number of ferrite rods,
which are arranged in a cylindrical pattern around a soft form. The
inductively-coupled gain boost provided by the tuned FSL antenna
depends upon the size and number of the ferrite rods, making it
desirable for a DXer to shop on eBay for the best bargains (usually
from the Eastern European sellers of Russian surplus rods). Both Steve
and Kevin were fortunate to have some of these rods available to make
early, effective FSL antenna models. My own situation wasn't nearly so
favorable-- in order to get a decent-sized FSL model constructed
promptly, I needed to order a serious number of ferrite rods through
the Amidon Corporation-- and pay some serious $$$.

My initial FSL antenna model (shown in a new photo album on
Ultralightdx) has 20 Type 33 ferrite rods (each one 4" x 1/2") wrapped
around a soft pipe insulation core, and wound with 55 turns of 670/46
Litz wire. The coil is connected in parallel with a 381 pf "N50P"
variable capacitor from, and tunes
from 280-1100 kHz as initially constructed. As shown in the photos
posted on Ultralightdx (and also at ), a PVC frame isolates the
antenna electrically, and protects the ferrite rods from accidental

Most hobbyists are probably wondering if and how the FSL antenna can
help them in their own DXing situations. The FSL's great advantage is
the ability to provide a concentrated DXing gain boost from a very
compact package. Whereas most high-gain antennas depend on sheer size
to accomplish the mission, the FSL accomplishes it from a very large
concentration of ferrite (with the side effects of concentrated cost
and weight :-) As long as a DXer accepts this tradeoff concept, he or
she will probably be quite satisfied with the antenna's performance. My
initial FSL model provides a very satisfying gain boost (by inductive
coupling) when the antenna's tuned MW or LW frequency matches that of
any Ultralight radio brought within its influence-- whether it's a
stock PL-606, a 7.5" LW loopstick PL-380, or even an ICF-2010. During
daytime DX testing yesterday I made a couple of MP3's of the FSL's gain
boost. The first was to a 7.5" LW "G" model loopstick PL-380 (a radio
which has already received over 100 NDB stations for me, Rob and
Patrick in its current form). Fringe daytimer 382-AW (Arlington, WA)
was received weakly for the first 3 ID's with the standard "G" LW
loopstick PL-380, and then with an inductive coupling boost from the
FSL: . In the second MP3, a
stock ICF-2010 struggles to receive the same 382-AW station at all for
the first 3 ID's, then the FSL comes to the rescue with a very large
gain boost: .

Steve, Kevin and I will no doubt continue to experiment with different
test models to choose the most practical designs for different
situations, but in general the antenna does seem to show excellent
potential for Ultralight radio DXers with limited space, especially
those in DXpedition situations where a picnic table is all that is

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

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