8" FSL vs. 4' Air Core Loop MP3 Impressions


Gary DeBock
 

<<< I could not hear the media clips, and explaining to me how to do
that would probably be a challenge. Could you briefly describe the
results or post the RSSI numbers if you recorded them?

I am guessing the FSL did very well, but wonder if it would be able to
be used anywhere near a computer or other home electronics? With my 4
foot air core loop or even my 2 footer, I can usually null out
electronics in the room, and still hear some signals, but of course the
ones the antenna pattern points to are much better than the ones in the
null for interference. The ferrite rod antennas you made for my PL 360
have a much tighter pattern than the air cores.

-FARMERIK >>>

Hello Farmerik,

The four fringe-station MP3's posted from the antenna testing are
fairly convincing, but for those who can't open the recordings, I'll
share my personal impressions.

The 8" FSL's reception advantage on the weaker stations is almost
entirely related to its lower noise pickup, and not superior signal
strength. On a couple of the fringe stations (1040-CKST and 1070-CFAX)
there was a fairly great difference between the FSL's relatively quiet,
noise-free reception and the 4' air-core loop's pickup of electrical or
atmospheric noise. The FSL's low-noise advantage is greater when
receiving the weaker stations, and it becomes less noticeable as the DX
station's signal strength increases. In rare cases the 8" FSL will
provide a slightly stronger DX signal than the 4' air-core loop, but
this is unusual, and the DX station signal levels are generally
equivalent on the two antenna systems.

The 8" FSL does have a few other advantages over the 4' air-core loop,
such as greater bandwidth (450-1700 kHz, as opposed to 530-1600 kHz)
and superior nulling performance. The FSL design also uses a high-Q
tuning system providing sharper selectivity, and can typically cut down
local station slop better than any air-core loop (this does requires
more careful tuning, however, making optimum signal peaking more of a
challenge) . Balanced against these advantages is the fact that the FSL
design has side effects of concentrated cost and weight, and requires
some protective padding for the ferrite components. In general the FSL
design does provide a high-gain DXing breakthrough for extremely
compact antennas, though, and is perfectly suited for the Ultralight
radio DXer who has only a picnic table for setup space.

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

-----Original Message-----
From: farmerik <farmerik@...>
To: ultralightdx <ultralightdx@...>
Sent: Thu, Jul 7, 2011 11:10 am
Subject: [ultralightdx] Re: 8" Diameter FSL vs. 4' Sided PVC Air-core
Loop Runoff

 
Gary - Thanks for all your experimenting and reporting of test
results. You and several others are doing a huge service to improve ULR
DXing results for all members.

Because I am a computer idiot, I could not hear the media clips, and
explaining to me how to do that would probably be a challenge. Could
you briefly describe the results or post the RSSI numbers if you
recorded them?

I am guessing the FSL did very well, but wonder if it would be able to
be used anywhere near a computer or other home electronics? With my 4
foot air core loop or even my 2 footer, I can usually null out
electronics in the room, and still hear some signals, but of course the
ones the antenna pattern points to are much better than the ones in the
null for interference. The ferrite rod antennas you made for my PL 360
have a much tighter pattern than the air cores.

-FARMERIK

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

Hello All,

With a DXpedition trip scheduled to the Oregon coast in about a
week
(with the family) and only enough space to pack a relatively
compact
antenna, it was time to choose the best performer for DU-chasing
this
summer.

The 4' sided portable PVC Loop had performed very well in the
August
20-22 DXpedition to Lincoln City last year, receiving over 30 South
Pacific stations when inductively coupled to to a C.Crane SWP
Slider
model (as described in the article posted at
http://www.mediafire.com/?9tjd0pqpa4ld2f0 ). But recently there has
&gt; been a lot of experimentation with Ferrite Sleeve Loop antennas,
indicating that these compact ferrite-based antennas provide a real
DXing breakthrough for hobbyists with limited setup space. As
such, it
was time to see if one of the new FSL's could really compete on MW
with
a proven DXpedition performer like the 4' portable PVC Loop.

An 8" diameter FSL was constructed w/ 63 Russian surplus 100mm x
10mm
ferrite rods, purchased on eBay from an Eastern European seller
(who,
presumably, is amazed at his recent financial bonanza). The
ferrite rod
&gt; assembly was secured on soft rubber form filled with padding
material,
&gt; then wrapped with 18 turns of 660/46 Litz wire from the eBay seller
&gt; "Mingmak222." A 381 pf variable capacitor from Crystal Radio Supply
(part # N50P) was used to tune the compact loop, providing
frequency
coverage from 450-1700 kHz. The design and construction of this
FSL was
&gt; chosen based on extensive A/B testing with another 8" diameter FSL
control model, and a photo of the FSL twins is posted at
http://www.mediafire.com/i/?pp9sa4pl56dm4kf (with the DXpedition
model
on the right, before MW frequency conversion).

At local noon here in Puyallup, WA four fringe stations were
chosen to
test the two compact loop systems, most of which were well over 100
miles distant. 550-KARI and 550-KOAC are fringe stations in the
Vancouver, BC and Portland, Oregon market, while 1040-CKST is a
station
in Vancouver, BC. 1070-CFAX is in Victoria, BC, and 1110-KWDB is in
Whitbey Island, northwest of Seattle. In all four MP3's the
reception
on the 4' sided PVC air core loop is first (about 15 seconds),
then the
reception on the 8" diameter FSL:

550-KARI-KOAC mix http://www.mediafire.com/?akf4xkx3sjwlwp3
1040-CKST http://www.mediafire.com/?jvcps6shc99i0q7
1070-CFAX http://www.mediafire.com/?bn16gdvoa2bdcnn
1110-KWDB http://www.mediafire.com/?ea3zczjet3mw1cj

Although the antenna testing was done with a completely open mind,
it
soon became quite clear which antenna provided a low-noise signal
advantage, especially on the weaker stations! The above recordings
were
all made on a stock PL-606 model, which was inductively coupled to
both
loop antennas at the optimum range. The new 8" FSL can easily be
converted to an "LW Optimized" antenna by switching in about 700
pf of
capacitance in parallel with the N50P variable cap, providing the
best
of both DXing worlds in a compact system taking up only one cubic
foot
of space. A photo of the relative size of these two antenna
systems is
also posted at http://www.mediafire.com/i/?yr7grir83488ii3 , which
hopefully will be of interest to picnic-table DXers like me!

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

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