Ferrite Sleeve Loop Antenna-- Medium Wave Testing MP3's

Gary DeBock

lo Raph (and All),

Thanks for your positive comments on the FSL design and testing. Steve
and Kevin have both done a lot of previous experimentation with FSL
antennas, and I've been fortunate to discuss the latest performance
tips with them.

As mentioned yesterday, Graham Maynard's new FSL design is a real
breakthrough in high-gain performance from a very compact antenna
system (although with some associated ferrite rod cost and weight
issues). When a large concentration of these ferrite rods is assembled
in a cylindrical pattern, the LW and MW performance of this compact
antenna can be astonishing.

This afternoon there was a chance to run some Medium Wave inductive
coupling tests with the new FSL here, boosting up the performance of a
stock Tecsun PL-606 (one of the most sensitive ULR's available) and
even the legendary full-size Sony ICF-S5W (one of the most sensitive
AM-DXing portables ever). A photo of today's testing lineup is posted
at http://www.mediafire.com/i/?vmxcezwdfdf0xy6 , in which the new FSL
antenna is shown to be of similar size to the ICF-S5W cabinet. The
first MW test was to check the FSL's gain boost to a stock PL-606,
tuned to the fringe daytime DX frequency of 550 kHz. Around local noon
here the barefoot PL-606 received nothing on 550 for the first 10
seconds of this MP3, then received the FSL's inductive coupling boost
for the last 15 seconds. The FSL's gain boost brought both 550-KARI (25
kw at about 150 miles) and 550-KOAC (5 kw at about 130 miles) out of
the noise, so that they were fighting it out on the frequency:

The same 550 kHz test was run on the full-size ICF-S5W, a very
sensitive AM portable which usually receives no benefit from
small-sized tuned loopstick systems (like the Quantum Loop). Not so
with the new FSL, though. A 550 kHz MP3 has the stock ICF-S5W
struggling with KARI for the first 7 seconds, then boosted
significantly by the FSL help: http://www.mediafire.com/?3nl6ldy4g4kfn5j

The final test was on 750-KXL (140 miles), which the barefoot PL-606
had at a fair level for the first 5 seconds, then at a strong level
with the FSL's gain boost: http://www.mediafire.com/?x9pnqxbuig2picd .
These MW tests confirmed that the new FSL design provides a powerful
DXing boost to portables of any size, a novel concept from a compact
antenna about the same size as the ICF-S5W (see photo). The exciting
thing is that this FSL is only of a relatively modest size (4.25" coil
diameter, with 20 ferrite rods). All three of the fanatical FSL
tinkerers have plans (or working models) twice this size-- and we
definitely plan to use them in all-out DXing! :-)

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

-----Original Message-----
From: Pollock,Raphael E <rpollock@...>
To: 'ultralightdx@...' <ultralightdx@...>
Sent: Wed, Mar 23, 2011 5:32 am
Subject: RE: [ultralightdx] Ferrite Sleeve Loop Antenna Testing

Dear Gary: Thank you for all the experimental work you, Kevin,and Steve
are performing, to the remarkable benefit of the rest of us! I amvery
impressed with your photo of the FSL—nice work w/ the pvc to
solvestability and brittle ferrite issues. Have you had a chance to see
how yourantenna performs in the MW DX contexts? I am looking forward to
your optimizeddesign! Raph Pollock From:ultralightdx@...
[mailto:ultralightdx@...] On BehalfOf D1028Gary@...
Sent: Wednesday, March 23, 2011 12:35 AM
To: ultralightdx@...
Subject: [ultralightdx] Ferrite Sleeve Loop Antenna Testing

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 http://www.crystalradiosupply.com,and tunes
from 280-1100 kHz as initially constructed. As shown in the photos
posted on Ultralightdx (and also at
http://www.mediafire.com/i/?r55ty7envel4ojx), 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 (aradio
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: http://www.mediafire.com/?del86caci4qm6a8. 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: http://www.mediafire.com/?n1ewt0mzp58e8v3.

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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