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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Sep Wed 10, 2014 5:19 am 
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Joined: May Wed 28, 2014 3:06 am
Posts: 6
Hello,

Unfortunately the construction cost of these FSL antennas makes them pretty tough to afford, unless someone has a pretty generous hobby budget. The most sensitive models (used primarily for ocean coast DXpeditions) have a construction cost pushing the $1K point, such as the all-new 17" DXpedition FSL (design photo posted at http://www.mediafire.com/view/n85a6ppdz ... hDXFSL.jpg ). But there are a couple of "Heathkit-like" construction articles for assembly of 5" and 7" diameter models, coasting about $150 and $200 respectively. For those who might be interested, a demonstration video of the 5" model's DXing performance in the reception of a daytime DX fringe station (at around 100 miles) is posted at http://www.youtube.com/watch?v=A1gfUeoQhHQ This type of FSL antenna model has DXing performance roughly equal to that of a 4' tuned air core box loop, and MP3 reception links are provided at the conclusion of the related article to document this. Good luck!


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Sep Thu 18, 2014 12:31 am 
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Joined: Dec Tue 18, 2012 5:04 pm
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Location: Vero Beach, Fl.
Just to let you all know Ming Mak mentioned that his supplier of ferrite material can make special runs of material. He may be able to get some of his R40C1 material in perhaps 7 or 8 inch rods. Not sure if bars or rods are preferable of what length might be the most beneficial? Thicker bars with beveled edges of something around 7" might be the best? I'm sure minimum order quantities would apply, but as much interest as there is in the FSL's we might be able to ad all the orders up and meet the minimum.


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Sep Thu 18, 2014 2:17 am 
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Hi Again Josh,

The question of whether to use ferrite rods or ferrite bars for maximum FSL sensitivity was covered in very extensive design experimentation a couple of years back, documented in the article posted at http://www.mediafire.com/view/6oyoldllr ... zation.doc

After Graham Maynard's introductory Ferrite Sleeve article was published in February of 2011 there were differing ideas about how to maximize FSL antenna sensitivity, and that article was an honest effort to start from scratch, and judge each design in actual A/B testing. Most (but not all) of the FSL antenna experimenters accepted the conclusions in the article, which I have used as a guideline for FSL design the past two years.

As for the ferrite mix, I'm pretty sure that Ming could come up with ferrite material superior to the Russian surplus rods made for the Red Army back in the 1990's :wink: Amidon's ferrite mix is also presumably far superior, but since the cost of ferrite material is the primary factor giving these antennas the nickname of "Financial Sinkhole Loops," the relatively cheap Russian surplus material continues to look pretty desirable (at least as long as the Ukrainian eBay sellers are left alone by Putin's "volunteers").


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Sun 15, 2015 5:58 pm 
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Joined: Feb Sat 22, 2014 1:40 am
Posts: 292
Hi Guys,
I have these potcores, is it worth me lashing them up for a try?
About 4.25" H x 7' OD
I have 2 more cores should I go 4 sets high with 3 in the circle.
About 8.5" H x 6" OD.
Mikek

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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Thu 19, 2015 12:53 pm 
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Joined: Oct Fri 08, 2010 10:28 am
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Location: Melbourne, Florida, USA
Hi Mikek, you'll never know until you try. Do you know what type material those are made of?
If you do experiment with these, it would be interesting to see the results.
What would you wind the coils with, litz? Anyway, good luck with your project!

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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Thu 19, 2015 3:35 pm 
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Joined: Aug Fri 29, 2014 6:17 pm
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Location: Vincennes Indiana
It'd be nice to be able to pulverize cores or just buy the dust and mold your own to suit. Then you could speriment with skin effects and so on.


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Thu 19, 2015 4:14 pm 
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I imagine you could pack the powder into PVC pipe, for the same effect.

A Q Meter would give a good indication of whether those cores might work in the BCB range. Wind a coil over them, and measure the Q at 1 MHz. A good ferrite would yield an exception Q.

Pete

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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Thu 19, 2015 9:40 pm 
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Posts: 292
NT9K wrote:
Hi Mikek, you'll never know until you try. Do you know what type material those are made of?
If you do experiment with these, it would be interesting to see the results.
What would you wind the coils with, litz? Anyway, good luck with your project!


I'm glad to see some finally responded!
I just made myself a form to put the cores in and decided to check in to see if anything was said.
For a first attempt I made 3 rods from the 12 cores. I wrapped a sheet of paper over it to keep
the wire from falling between cores. I had a piece of wire (13ft), I wrapped it and got 8 turns.
I tested it and found it resonant at 1388kHz with 475pf. My mind is mechanical today, don't
want to do any math, but I think ? doubling turns quadrupals inductance, so if I double it twice
I will have about 230 microHenries.
I did put a radio near it and it did enhance the signal at 1260 kHz even though I could only tune
down to 1388kHz.
It's a start.
Mikek
PS. I wanted to post a picture but my files are to big, what do you guys use to
reduce the file size for pictures?


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Thu 19, 2015 11:16 pm 
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qmavam wrote:
For a first attempt I made 3 rods from the 12 cores. I wrapped a sheet of paper over it to keep
the wire from falling between cores. I had a piece of wire (13ft), I wrapped it and got 8 turns.
I tested it and found it resonant at 1388kHz with 475pf. My mind is mechanical today, don't
want to do any math, but I think ? doubling turns quadrupals inductance, so if I double it twice
I will have about 230 microHenries.
I did put a radio near it and it did enhance the signal at 1260 kHz even though I could only tune
down to 1388kHz.
It's a start.
Mikek
PS. I wanted to post a picture but my files are to big, what do you guys use to
reduce the file size for pictures?

You might try unwinding one turn of wire, to see how it changes the resonant frequency.

AFA pic file size; my own camera does 1600 x 1200 pixels, so I just use Windows Paint Shop, and reduce by 50%, to 800 x 600, which is then within forum limits.

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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Thu 19, 2015 11:46 pm 
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Joined: Feb Sat 22, 2014 1:40 am
Posts: 292
I ended up with 21 turns wide spaced.
One of my locals 590kHz is producing 90 mvpp setting on my bench,
with all the equipment and metal around.
I don't know what to expect.
I need to do some more measurements on another day.
The material is 3C81,supposed to be good to 2 or 3 MHz,
but I think I saw a large drop in Q at higher frequency.
Q= 114 at 530kHz and Q = 16 at 1407kHz, but thta's so bad
I need to recheck it.
I used a solid #16 wire, don't want to waste my Litz until I have a
feel for what's going on.
Thanks, Mikek


Attachments:
FSL 3 rods.jpg
FSL 3 rods.jpg [ 140.06 KiB | Viewed 5304 times ]
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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Fri 20, 2015 4:55 am 
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Joined: Feb Sat 22, 2014 1:40 am
Posts: 292
I rechecked this evening, and my Q= 113 at about 530kHz
and a very dissappointing Q=17 at 1350kHz. About the same
as I measured earlier today.
I think the material losses increase at the higher frequency.
When I tuned it to my local 590kHz I get 0.175 Vpp when
the signal is at peak modulation.
Any thoughts?
Mikek


Attachments:
3 rod coil 21 turns.jpg
3 rod coil 21 turns.jpg [ 217.06 KiB | Viewed 5284 times ]
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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Fri 20, 2015 9:39 pm 
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Joined: Feb Sat 22, 2014 1:40 am
Posts: 292
[quote="DXerGary"]Hello,
such as the all-new 17" DXpedition FSL (design photo posted at http://www.mediafire.com/view/n85a6ppdz ... hDXFSL.jpg ).

What is the Q of the FSL at the high and low end?
Mikek


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Fri 20, 2015 10:31 pm 
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Joined: Aug Fri 29, 2014 6:17 pm
Posts: 2581
Location: Vincennes Indiana
You might try spacing the wire away from the cores, such as with some foam sheeting or similar method.


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Fri 20, 2015 11:55 pm 
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Joined: Feb Sat 22, 2014 1:40 am
Posts: 292
db gain wrote:
You might try spacing the wire away from the cores, such as with some foam sheeting or similar method.


Ya, I wanted to do that, but a search of garage and shop didn't pullup
any foam to use.
Do you have any theory that doing so would increase the high frequency Q?

I looked up the datasheet, the material losses are high at frequencies much lower
than I expected. We used it at 660kHz regularly and a 1 MHz on occasion, at power
in the 100s of watts, in a smaller core.

The spec's look bad for this use.
http://allstarmagnetics.com/assets/3c81.pdf

I have a lot of ferrite pot cores, but nothing like the size of these cores.
Mikek


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Sat 21, 2015 4:25 am 
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Joined: Aug Fri 29, 2014 6:17 pm
Posts: 2581
Location: Vincennes Indiana
As to spacing, there was something Dallas Lankford wrote in one of his antenna speriments that involved spacing the turns from the rods. If I come across it I'll direct you to it. Otherwise peruse google;
https://www.google.com/search?q=dallas+ ... rd+ferrite


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Sat 21, 2015 4:35 am 
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Joined: Feb Sat 22, 2014 1:40 am
Posts: 292
db gain wrote:
As to spacing, there was something Dallas Lankford wrote in one of his antenna speriments that involved spacing the turns from the rods. If I come across it I'll direct you to it. Otherwise peruse google;
https://www.google.com/search?q=dallas+ ... rd+ferrite


I followed Dallas since about 1995 when he was working on the Slotka/Lankford phased antenna.
I built one and had lot of fun with it.
I followed his Yahoo forum also, it's to bad he took it down.
Have you heard about him or anything he's working on?
Thanks, Mikek


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Sat 21, 2015 7:31 pm 
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Joined: Aug Fri 29, 2014 6:17 pm
Posts: 2581
Location: Vincennes Indiana
I just emailed him, will see what he has to say, if anything.


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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Sat 21, 2015 7:52 pm 
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Joined: Feb Sat 22, 2014 1:40 am
Posts: 292
db gain wrote:
I just emailed him, will see what he has to say, if anything.


Good, it will me interesting to see if he has worked with FSL antennas.
I remember early on he worked with bundled ferrite rods.

I took my FPCTRA ( Ferrite PotCore TriRod Antenna), hope that doesn't stick :-)
out into the yard just now. I only worked at the low end 530kHz to 550kHz.
I certainly made a huge difference in signal. I went from a signal that at full volume
I could tell something was there to, I had to turn it to under half volume and it was very clearly
understood. One station was just not there until I got the radio close to the FPCTRA then I
had a station clearly understandable, well except it was Spanish. Either Cuba or Miami.
I'm in Panama City Florida. I set it up so I could rotate it and found two stations on the
same frequency, I could null either one to hear the other. BTW, you can get the radio to close,
you need to space it 2" to 3" away.
The ferrite material may make a decent LW antenna, but I need some more info about
the Q's FSL makers are getting. If they are getting Q's of 500 or 600 and I get 114, it's probably
better to sell the cores and invest in a better material for the AM band. These 12 cores list at $278.
I got them after a business closed.
Mikek


Last edited by qmavam on Feb Sun 22, 2015 3:10 am, edited 1 time in total.

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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Sun 22, 2015 12:02 am 
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Quote:
BTW, you can get the radio to close, you need to space it 2' to 3" away.

Is that 2 - 3 Feet or 2 - 3 Inches?
I suspect it was not supposed to be 2 Feet to 3 Inches.

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 Post subject: Re: Ferrite Sleeve Loop antennas: Are they for real?
PostPosted: Feb Sun 22, 2015 3:13 am 
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Joined: Feb Sat 22, 2014 1:40 am
Posts: 292
Willitwork wrote:
Quote:
BTW, you can get the radio to close, you need to space it 2' to 3" away.

Is that 2 - 3 Feet or 2 - 3 Inches?
I suspect it was not supposed to be 2 Feet to 3 Inches.


It's inches, I edited it.
I think it's time to look into a video camera, I wanted to post a video, I grabbed my camera that will record
video, then I recalled it doesn't record audio, that's not good for showing radio reception.
Mikek


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