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 Post subject: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Tue 18, 2014 1:37 am 
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Joined: Feb Sat 08, 2014 7:43 pm
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Location: Denver, CO
I've been out of the loop (bad pun intended) and hadn't heard of the FSL antenna until recently. Google and YouTube have turned up plenty of positive things about the FSL, but I'd like to hear from someone on this forum with personal experience. It sounds like an exciting development and a real boon to BCB enthusiasts. There seems to be controversy over the physics involved, but I'm no physicist so don't care about that....I'd just like to know if this antenna is the "real deal".

Thanks.


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Wed 19, 2014 2:48 am 
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Location: Mpls, Minnesota
Interesting concept, I may have to build one of those.

Dave


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Wed 19, 2014 6:02 pm 
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The guy in the youtube vid said materials = $200
:|


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Thu 20, 2014 5:27 pm 
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Joined: Feb Sat 08, 2014 7:43 pm
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Location: Denver, CO
Cost is the big downside. Some guys refer to the FSL as the "Financial Sinkhole Loop". The situation is getting worse as the supply of surplus ferrite rods from former Eastern Bloc countries dries up. The Rooskies have caught on to supply-and-demand economics; no more ferrite rods at a buck apiece from Ukraine, comrades!

As an experiment, I strapped together this "micro FSL" antenna from some ferrite bars. I've had these for ages and don't remember the source. I removed the coil winding from 6 of these bar antennas, taped the bars into a roundish bundle, and wrapped it with about 40 turns of #24 magnet wire. Measured inductance was 187 microhenries. My junkbox had a tuning cap with vernier, and this LC combination covers most of the broadcast band. This was enough for me to run some quick experiments with an AM radio.

The increase in receiver sensitivity is very strong, though I don't have a way of quantifying that with measurements other than my ears. I'm able to pick up stations otherwise not audible with the radio alone. I definitely need the vernier tuning for the FSL cap, as the tuning is sharp. BTW, the "sweet spot" for distance is about 2 inches spacing between the FSL coil and the radio.

This exercise was fun, and I'm impressed with the performance increase of my little radio, but I'm not sure if I've proven anything about the FSL concept. All I've done is supplement my radio's internal antenna with an antenna of larger area. I might have had the same result with a 2 or 3 foot wire loop.


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File comment: Spacing is critical, about 2 inches distance from coil to radio
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File comment: Not the neatest coil, but It'll have to do...
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File comment: I had six of these in my parts stash. The coil easily slides off the bar.
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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Fri 21, 2014 11:25 am 
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Very interesting! I have a number of Ferrite bars from junked Transistor sets. I'll have to build one of these sometime soon, and compare performance to my 23" tunable loop.

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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Fri 21, 2014 3:00 pm 
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Two key parameters for any antenna: Aperture and Impedance matching. If I am not mistaken, Ferrite antennas are a way of getting the right impedance in a small space. If 2 Ferrite antennas are both correctly matched to the RF input stage, then I would expect the physically larger one to have the better performance.

Can anyone post a short summary of why the "Sleeve Loop" is supposed to be better? (excluding the fact that it might be larger....)

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"Voltage is fun to watch, but it's the CURRENT that does the work."


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Sat 22, 2014 3:19 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Saskatoon
pixellany wrote:
Can anyone post a short summary of why the "Sleeve Loop" is supposed to be better? (excluding the fact that it might be larger....)

The only write up I've seen, that tries to explain it, involves rewriting the laws of physics. It kinda falls into the over-unity branch of pseudo-science.

Here it is:
http://www.zen22142.zen.co.uk/Media/fsi.htm
Put on your BS filter, and have a good laugh.

As you've noted, if it works well, then it's mainly due to it's larger size, and nothing else.


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Sat 22, 2014 10:21 am 
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Quote:
Here it is:
http://www.zen22142.zen.co.uk/Media/fsi.htm
Put on your BS filter, and have a good laugh.
Good grief!!

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-Mark
"Voltage is fun to watch, but it's the CURRENT that does the work."


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Sat 22, 2014 11:45 am 
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http://www.zen22142.zen.co.uk/Media/fsi.htm

Image

Kinda reminds me of a Gatling Gun... :wink:

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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Sat 22, 2014 3:11 pm 
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Joined: Feb Sat 08, 2014 7:43 pm
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Location: Denver, CO
Found this article on FSL design. Bottom line: Performance is directly proportional to antenna area. No big surprise there.

http://www.am-dx.com/antennas/FSL%20Ant ... zation.htm

The concept seems sound, but it's unfortunate the original developer (Graham Maynard) discredited himself with pseudo-scientific explanations.


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: May Wed 28, 2014 4:10 am 
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Hello, This is Gary, one of the primary ferrite sleeve loop antenna experimenters (and also, the weird dude that you see on the demonstration videos) . I very much enjoyed the account (and photos) of Pentagrid's tiny antenna test, and hope that you will continue to tinker around with the new antennas. After about 3 years of extensive testing and refinement, I can assure you that the ferrite sleeve loop antennas are indeed a "real deal," and provide a major breakthrough in compact antenna DXing performance. Unfortunately, the most sensitive models also come with the side effects of serious cost and weight. This tradeoff makes the antennas somewhat of a specialty item, most useful in extremely narrow spaces like ocean side cliffs. Good luck in your own experimentation!


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: May Wed 28, 2014 5:45 pm 
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Joined: Feb Wed 12, 2014 4:25 pm
Posts: 153
Location: Southeast Kans. - KA0HCP
A little bit of hokum.

Antenna Effective Aperture is not governed by 'area' or the amount of metal used. It is governed by antenna design Gain. Owen ex-VK1OD is an RF engineer
https://web.archive.org/web/20130321175 ... pts/Ae.htm

You can't just slap more ferrites together or form them into a tube and expect correct performance. Antenna coils, ALL coils, are designed for specific frequencies and bandwidth ('Q"). Change the ferrite Mix, Size, Shape; wire size, number of turns, turn spacing, coil diameter, insulated/non-insulated and the coil resonant frequency and Q will change.

If the experimenters found some improvement, it was accidental. They probably did not do complete measurements which would have shown reduction or changes in other desirable performance parameters.

Save your money, and help discourage bogus antenna ideas like this. Study the formulas; do the math!

http://en.wikipedia.org/wiki/Ferrite_core

http://www.amidoncorp.com/specs/
Amidon is the major manufacturer of ferrite material in the US

http://www.fair-rite.com/newfair/index.htm
http://www.fair-rite.com/newfair/materials.htm
Fair Rite is one of the major distributors and has good prices. Mix types described. Choose the CORRECT mix for your application. Using random ferrite material is silly and a waste of money.

http://www.fair-rite.com/cgibin/catalog ... lect:freq1
Catalog page with antenna ferrite rod applications and formula.

bill


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: May Wed 28, 2014 5:56 pm 
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Joined: Feb Wed 12, 2014 4:25 pm
Posts: 153
Location: Southeast Kans. - KA0HCP
continued...

-What you need to know is the designed Inductance of your antenna coil at desired frequencies!

Either get this from your radio schematic, use measurement devices (at the correct frequencies) or reverse engineer by unwinding the coil, counting turns, measure turn spacing, measure wire diameter and insulation and estimating the rod mix.

-Stronger signal is not always better!
Don't forget about Front End Overload which will cause distortion, uncomfortable listening, decreased selectivity, AGC Pumping, etc. You may need to add a coupling capacitor, resistor or T-pad to reduce signal strength.

b.


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: May Thu 29, 2014 12:28 am 
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Joined: May Wed 28, 2014 3:06 am
Posts: 6
Hello KB4QAA,

Thanks for your reply. My original post was in response to the inquiry from Pentagrid, who was asking for more information about the FSL antennas from one of the actual experimenters.
A lot of the confusion and skepticism of the FSL antenna design originated from Graham Maynard's introductory article in February of 2011, which contained some rather outlandish scientific claims. The FSL experimenters (like me) were not interested in the scientific claims, but were interested in whether the design would provide a breakthrough in compact DXing performance relative to the tunable air-core box loops used for medium wave reception for many decades. As such, very detailed A/B testing was done with different sizes, shapes and components to determine whether the FSL antennas would provide such a breakthrough (as detailed in the article linked above, in Pentagram's last post).
The medium wave DXing community has generally accepted the compact performance breakthrough that these antennas provide, especially in the reception of transoceanic DX stations on narrow ocean side cliffs. Those who specialize in this type of DXing (like Chuck Hutton, here on the west coast) admit that their weak signal reception is unprecedented for such a small antenna. Performance videos (like the one posted on YouTube) leave little doubt that the design does work, although the cost of constructing these compact antennas can be quite high.

73, Gary (N7EKX)


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: May Fri 30, 2014 2:34 pm 
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Joined: Mar Sat 22, 2014 10:17 am
Posts: 29
Hello Gary and thank you for your efforts in this area. After building a 2' square air core loop, I saw your video for the 5" FSL antenna and decided to build one similar. Mine has (40) 8mm x 130mm rods and is about 4.5" in diameter. I did not have any Litz wire, so I used some 24 AWG 19/36 wire that I had on hand. It performs as well, if not better, than the 2' loop. The total cost was around $50.

Best regards,
Trey


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: May Fri 30, 2014 9:01 pm 
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Joined: May Wed 28, 2014 3:06 am
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Hello Trey,

Thanks for your message, and for the interesting photo. Congratulations also on the successful completion of your 5" FSL antenna project-- and I'm honored to have played a small part in your success.

To my knowledge, about 7 different DXers have completed the "Heathkit-like" assembly instructions for the 5" FSL antenna project (at the link posted on the YouTube demonstration video), and all have reported good results with the antenna. Substitute 120mm x 8mm ferrite rods are still available on eBay at fairly reasonable prices (50 rods for $39, before shipping), and work almost as well as the 140mm x 8mm rods called for in the article. Anyone interested in FSL antenna design, construction or performance can find a wealth of information posted in our Ultralight Radio Yahoo group (Ultralightdx), including design photos, construction articles and DXpedition reports (complete with MP3 recordings of transoceanic AM-DX stations received with the innovative antennas on narrow ocean side cliff sites). Thanks again for your response, Trey, and have fun with your new antenna!

73, Gary (N7EKX)


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: May Sat 31, 2014 1:11 pm 
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Gary, I was wondering if you have done much experimenting with different wire and the spacing between each turn. I originally placed the wire in the center as you show in your video and it worked fine that way and was going to buy some 660/46 Litz but changed my mind when I saw the price and then later came across an article by Graham Maynard. He suggested that Litz was not required and also a different spacing covering nearly all the length of the rod. I took his suggestion and it worked better for my application which is limited to commercial AM radio frequencies. Thank you again for sharing your findings with others such as myself.

Best regards,
Trey


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Jun Sun 01, 2014 12:27 am 
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Hi Trey, Graham's initial article on the ferrite sleeve antenna was the starting point for intensive experimentation in our Ultralight radio group, but we substituted almost every possible component (and every possible physical layout) in an effort to gain even more sensitivity from the antenna. We all discovered that large diameter Litz wire gave a performance boost relative to the magnetic wire, with the largest diameter Litz wire providing the most sensitivity. Of course (as you have discovered) the larger diameter sizes like 660/46 cost quite a bit more than the smaller sized Litz wire, so there is a price/performance tradeoff that each builder must consider. Even the magnetic wire models do provide a potent inductive coupling boost when tuned on frequency, though, so they are a good choice if reasonable cost is important. On the other hand, the no-compromise 15" diameter FSL antenna models designed for transoceanic Medium Wave DXing on ocean side cliffs use the new 1162/46 Litz wire, which runs almost $1 per foot on eBay.

Multiple coil configurations (contra-wound, Polydoroff, spread out and/or parallel) were also tried by various FSL experimenters, and the spread out configuration was found to be useful in extending the bandwidth of the single-band models (so long as there was enough space on the ferrite rods to accommodate such a system). As you might imagine with three major experimenters each going their own chosen direction, there were some differences of opinion related to ferrite rods Vs. ferrite bars, thick ferrite Vs. thin ferrite, and the factors which determined ultimate FSL antenna sensitivity. The extensive FSL Design Optimization article (posted at http://www.am-dx.com/antennas/FSL%20Ant ... zation.htm ) detailed my own efforts to provide some clarity in the design parameter discussion, but of course it was impossible to include such variables as multiple coil orientations. As such, there still are some differences of opinion related to their importance in providing additional FSL antenna sensitivity. 73, Gary


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Jun Sun 01, 2014 12:43 am 
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I don't know how drastic the signal improvement is but I certainly have noticed that when I place two radios close to each other with their backs about 2 inches apart, one radio is powered off. Then if I tune the live radio to any station and the "off" radio to the same station.. the live radio signal is considerably stronger.
The passive antenna tuned circuit in the powered-off radio ..will induce a greater signal into the live radio's antenna.

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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Sep Wed 10, 2014 4:12 am 
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Joined: Dec Tue 18, 2012 5:04 pm
Posts: 30
Location: Vero Beach, Fl.
DXerGary wrote:
Hi Trey, Graham's initial article on the ferrite sleeve antenna was the starting point for intensive experimentation in our Ultralight radio group, but we substituted almost every possible component (and every possible physical layout) in an effort to gain even more sensitivity from the antenna. We all discovered that large diameter Litz wire gave a performance boost relative to the magnetic wire, with the largest diameter Litz wire providing the most sensitivity. Of course (as you have discovered) the larger diameter sizes like 660/46 cost quite a bit more than the smaller sized Litz wire, so there is a price/performance tradeoff that each builder must consider. Even the magnetic wire models do provide a potent inductive coupling boost when tuned on frequency, though, so they are a good choice if reasonable cost is important. On the other hand, the no-compromise 15" diameter FSL antenna models designed for transoceanic Medium Wave DXing on ocean side cliffs use the new 1162/46 Litz wire, which runs almost $1 per foot on eBay.

Multiple coil configurations (contra-wound, Polydoroff, spread out and/or parallel) were also tried by various FSL experimenters, and the spread out configuration was found to be useful in extending the bandwidth of the single-band models (so long as there was enough space on the ferrite rods to accommodate such a system). As you might imagine with three major experimenters each going their own chosen direction, there were some differences of opinion related to ferrite rods Vs. ferrite bars, thick ferrite Vs. thin ferrite, and the factors which determined ultimate FSL antenna sensitivity. The extensive FSL Design Optimization article (posted at http://www.am-dx.com/antennas/FSL%20Ant ... zation.htm ) detailed my own efforts to provide some clarity in the design parameter discussion, but of course it was impossible to include such variables as multiple coil orientations. As such, there still are some differences of opinion related to their importance in providing additional FSL antenna sensitivity. 73, Gary





Gary,

What is the cost of your 15" FSL monster? I am curious how one of these FSL's would work when using it in a crystal radio mode. My large double tuned 8 foot Litz crystal radio is way too large to be mobile while these FSL counterparts could be the ticket.


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