8" Diameter FSL vs. 4' Sided PVC Air-core Loop Runoff


Gary DeBock
 

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
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
assembly was secured on soft rubber form filled with padding material,
then wrapped with 18 turns of 660/46 Litz wire from the eBay seller
"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
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)


Michael <michael.setaazul@...>
 

Thanks for the nteresting, informative report, Gary!
Would it be possible to do a three-fold
comparison, including LW, between
the 4' loop, the FSL and a single-ferrite
such as the 7" loopstick, all inductively
coupled?

Cost unfortunately renders the FSL unfeasible,
and the big loop is unwieldy, so it would be
valuable/comforting to know to what degree
the basic single-ferrite would be inferior.

There was mention of a basic FSL with fewer
ferrites spaced round the tube, but I have
not seen any further reference to this.
Not worth persuing further?

What would happen if ferrites of different
origins, lengths and quality from old
radios were used in a compromise FSL?

As an off-shoot, I would like to have a
compact performing LW/MW receiver
with a genuinely portable antenna.
It would have to be either a single ferrite
or a small loop.

I am also interested in phasing out local
interference from CFLs and digital sources
by using a second aerial and a cancelling
circuit. Is there any information on this aspect
in the group?

Michael UK


Rik
 

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
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
assembly was secured on soft rubber form filled with padding material,
then wrapped with 18 turns of 660/46 Litz wire from the eBay seller
"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
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)


Gary DeBock
 

Hello Michael,

Thanks for your interest in Ferrite Sleeve Loop antennas, and for your
comments on my post.

<<<Would it be possible to do a three-fold
comparison, including LW, between
the 4' loop, the FSL and a single-ferrite
such as the 7½" loopstick, all inductively
coupled?
Cost unfortunately renders the FSL unfeasible,
and the big loop is unwieldy, so it would be
valuable/comforting to know to what degree
the basic single-ferrite would be inferior. >>>

Yes, it certainly would be possible to do such a comparison, although
because of limited experimental time here it's probably a little too
ambitious to consider for the near future. In general a 7.5" loopstick
(MW or LW) provides a quantum leap in DXing sensitivity over a stock
Tecsun loopstick, and a serious-sized FSL (8" or larger) or air core
tuned passive loop (4' side or larger) provides another quantum leap in
sensitivity over the 7.5" loopstick. Regarding the relative reception
capabilities of a 7.5" MW loopstick and a stock Tecsun-built model,
detailed TP-DXing records were kept during a November 2008 DXpedition
to Grayland, Washington, showing the huge sensitivity advantage
provided by a transplanted 7.5" loopstick in an Eton E100 model. This
"E100 Four Variant Shootout" article may be of interest to those who
have wondered about this sensitivity advantage
http://www.mediafire.com/?mjmn0xijxod . For those looking for an
additional signal boost, I've personally had very good results with
smaller air-core loops (2' and 3' sided) and FSL's (4" diameter),
either of which can provide some additional MW or LW sensitivity beyond
that of a 7.5" loopstick.

<<<There was mention of a basic FSL with fewer
ferrites spaced round the tube, but I have
not seen any further reference to this.
Not worth pursuing further?>>>

Both Steve and Kevin (among others) have done extensive FSL
experimentation before me, and I had a pretty late start because of a
need to finish up 7.5" Longwave loopstick testing. I did some limited
testing of a basic FSL with spacing between the ferrites, but was not
satisfied with the results. Others who have done such testing may have
other impressions, and I welcome their comments. In general (because of
limited time), my objective was to determine whether the FSL design
would provide a compact DXing breakthrough over existing antennas, and
devote the necessary resources to test out the most effective designs
as soon as possible. Presumably, the eBay sellers of surplus Russian
ferrite are extremely grateful for this kind of attitude, and for the
additional contributions of Steve and Kevin :-)

<<<What would happen if ferrites of different
origins, lengths and quality from old
radios were used in a compromise FSL?>>>

It's tough to give an accurate answer about this because nobody has yet
tried it, to my knowledge. The results would probably depend on the
size, quality and consistency in the ferrite rods, but it's doubtful
that any such composite FSL would be competitive with the larger,
standardized designs, in my opinion.

<<<As an off-shoot, I would like to have a
compact performing LW/MW receiver
with a genuinely portable antenna.
It would have to be either a single ferrite
or a small loop.>>>

This was the concept behind the recent development of the 7.5" MW and
LW loopsticks for the Tecsun DSP models, Michael. These loopsticks have
sensitive performance compared to the stock Tecsun antennas, and there
have been many positive comments about their DXing results.
Unfortunately there isn't much time here to make more of them in
quantity, but the MW version article is posted at
http://www.mediafire.com/?yummxhqeyjy , and the LW version article is
posted at http://www.mediafire.com/?845snah2h4ek9z9 . A PL-380 model
may be modified to accept either 7.5" loopstick (MW or LW) in a plug-in
design, or a stock PL-360 model will accept either loopstick without
the need for modification.

<<<I am also interested in phasing out local
interference from CFLs and digital sources
by using a second aerial and a canceling
circuit. Is there any information on this aspect
in the group?>>>

None that I am aware of, Michael. I know that this has been done
extensively in the amateur radio community with noise-canceling
antennas and phasing units, but not in relation to CFL's with
Ultralight radios.

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

-----Original Message-----
From: Michael <michael.setaazul@...>
To: ultralightdx <ultralightdx@...>
Sent: Thu, Jul 7, 2011 12:42 am
Subject: Re: [ultralightdx] 8" Diameter FSL vs. 4' Sided PVC Air-core
Loop Runoff

 
Thanks for the interesting, informative report, Gary!
Would it be possible to do a three-fold
comparison, including LW, between
the 4' loop, the FSL and a single-ferrite
such as the 7½" loopstick, all inductively
coupled?

Cost unfortunately renders the FSL unfeasible,
and the big loop is unwieldy, so it would be
valuable/comforting to know to what degree
the basic single-ferrite would be inferior.

There was mention of a basic FSL with fewer
ferrites spaced round the tube, but I have
not seen any further reference to this.
Not worth pursuing further?

What would happen if ferrites of different
origins, lengths and quality from old
radios were used in a compromise FSL?

As an off-shoot, I would like to have a
compact performing LW/MW receiver
with a genuinely portable antenna.
It would have to be either a single ferrite
or a small loop.

I am also interested in phasing out local
interference from CFLs and digital sources
by using a second aerial and a canceling
circuit. Is there any information on this aspect
in the group?

Michael UK