ferrite sleeve antenna? - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: February 01, 2021, 11:59:22 pm
content: Has anyone used this weird antenna before?https://dxer.ca/articles/92-gary-debockof course I want to build one of those too, it seems the antenna projects just stacked up this winter.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 02, 2021, 03:10:03 am
content: Eh, length is better than girth...The cross section doesn't really matter, and a hoop/sleeve/shell/pipe is fine. Above a certain thickness, little field will even reach the middle of a solid rod anyway (skin effect).Tim

author: coppercone2
author_rank: Super Contributor
timestamp: February 02, 2021, 03:57:34 am
content: this one seems to have people debating about it in different placesover unity seems to be getting involvedthe damn website everyone keeps referring for MW and LW work with this type of antenna with experimental results that supposedly justify it is downwww.AM-DX.comI know normally you want something like 10/20:1 ratio of length of ferrite to coil on it, this thing is pretty alien.regenfreak is going at it pretty hard if you scroll down this threadhttps://www.antiqueradios.com/forums/viewtopic.php?f=12&t=244138&start=40The bottom of the page he hooks up a Q meter with a de5000 on it.Dunno what normal is or if its better but usually the odin loop free energy fuckwits don't get as far as a Q meter. I have yet to decypher this but it must be something hard confusing these people if this antenna does not work because their fairly well equipped and able to understand specifications of materials etc.

author: coppercone2
author_rank: Super Contributor
timestamp: February 02, 2021, 04:54:23 am
content: https://www.angelfire.com/electronic2/index1/Green-Giant-FSL-Summary.pdfWhat I am guessing is that it must have given them a better performance being wide then long, even if thats the convention. But it is annoying not to see any graphs or power measurement etc.I guess I am wondering, can something better be made with the same materials or even materials cost? I am surprised all those gaps don't make for problems with those ferrites touching circle edge to circle edge.here is a video of a person playing with a few of themAny idea why the ferrite rod model needs the radio to the side when the ferrite bar model wants the radio in front? Does it have something to do with fringe fields?If you use those ferrite bars, it looks like its possible to get a nice many sided shape with them if cut, painstakingly.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 02, 2021, 05:14:09 am
content: The high Q, narrow tuning whatever, at the very least puts a ceiling on how much radiation resistance (coupling to far field) it has.But that's as expected, electrically short dipoles have that coupling roughly proportional to length over wavelength.The dipole moment is all that matters. Which increases with overall dimension (say of a bounding sphere). The point of using a ferrite rod is to use a smaller coil than a plain (air core) loop of the same size. Hence, loopstick.Tim

author: A.Z.
author_rank: Super Contributor
timestamp: February 02, 2021, 05:11:59 pm
content: Quote from: coppercone2 on February 01, 2021, 11:59:22 pmCheck out thesehttps://swling.com/blog/tag/ferrite-sleeve-loop/

author: ChristofferB
author_rank: Frequent Contributor
timestamp: February 03, 2021, 08:56:21 am
content: Empirical design goes a long way in antenna design, and is a time-honored tradition.That said, it always makes me suspicious when stuff like this is presented as long streams of text with little actual data.

author: coppercone2
author_rank: Super Contributor
timestamp: February 03, 2021, 09:28:23 am
content: I thought the video was interesting but what is the deal with the ferrite bars and ferrite rods having a different magnetic coupling? pattern to the radios loopstick?

author: A.Z.
author_rank: Super Contributor
timestamp: February 03, 2021, 02:21:44 pm
content: Quote from: coppercone2 on February 03, 2021, 09:28:23 amI think you may start by reading thishttp://www.zen22142.zen.co.uk/Media/fsi.htmand then follow up with thesehttp://vk4ebp.com/project%20-%20Ferrite_Sleeve_Loop.htmlhttps://www.antiqueradios.com/forums/viewtopic.php?f=12&t=244138http://theradioboard.com/rb/viewtopic.php?t=7041

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 03, 2021, 04:41:12 pm
content: Bahaha, that's some serious woo right there!Tim

author: A.Z.
author_rank: Super Contributor
timestamp: February 03, 2021, 05:57:45 pm
content: well ... yeah, but at least it may be a starting point

author: coppercone2
author_rank: Super Contributor
timestamp: February 04, 2021, 03:22:31 am
content: hmm the problem is the chokes. I have a bunch of ferrite tiles from a broken induction stove but they are various lengths. Do you think this makes any sense to make if the ferrite ring is 2.5 inches long? They look like they have 9 inch cores in the pictures and videosThe best one I can do for free would be around the size of a bean can wrapped with ferrite strips that are 2.5 inches long and something like 12mm wide and 3mm thick. I might have some slightly damaged litz wire from a induction cooker also.I think I can cut the ferrite strips to uniform length using diamond water cooled tile saw. The induction stove top I had taken apart had 4 burners, each with different length tiles.But with this size, is it worth doing at all? I obviously do not want to spend any money on this, save for maybe getting some litz wire because its otherwise interesting for other reasons.

author: regenfreak
author_rank: Contributor
timestamp: February 18, 2021, 02:52:59 pm
content: hiForget about pseudoscience and subjective evaluation. That guy discredits himself with those crazy writings.For my 75 ferrite bars, 1 feet diameter, giant super ferrite sleeve, I made the costly mistake of using 3mm thick 500 strands of 0.1mm Litz which is optimised for below 200kHz. I got Q near and over 2000 at 100kHz with the DER DE-5000. I will replace the 500 0.1mm Litz by 660/46 in spaced windings. At the moment the Q is poor for MW frequencies., I did measurement using a Q-meter developed by a Chinese Ham Mr Gao. It reads Q=200 at 1.2MHz. I have got the 660/46 Litz from Ming (a crystal radio builder in the USA who also owns an ebay store). Mr Gao's Q meter gives readings are consistent with the De-5000 at similar frequencies. Gao's meter is based on the simple method of ring-down technique that can be done using a scope and a synch square pulse wavelength trigger...you count the number of damped cycles on the scope and work out the Q indirectly. Mr Gao Q meter makes it automatic and is accurate for high Q measurements.It is very difficult to Q measurement when Q is over 1000. Most cheaper Q-metesr cannot measure Q over 500. I tested the air variable capacitor of my Heathkit Q-meter, it uses aluminium plates and has low Q. The moment you attach a high Q coil to a normal variable air capacitor, the Q drops by 50%. A surefire Q-killer. I am looking for untarnished, silver-plated air variable capacitor for Q measurement.I will also replace the blue foam core by 2.5 litre HDPE water bottle. The tangent loss of HDPE is lower than high-density blue foam used in aqua dumbells. White PVC pipe has higher tangent losses than HDPE.In addition, I also got some "magic" R40C12 toroids and bars from Ming. Now this is very impressive. I got the Q reading of over 1200 for two 38mm diameter R40C1 stacked toroids with 270/46 Litz. They got Q over 1400 at different frequencies and winding techniques. I have been playing with different winding configurations; "contra-winding" and space-winding to optimise the Q.I am waiting to buy the NanoVNA v2 Plus 4 :-*which has a dynamic range of 90db. It is out of stock. I have the NanoVNA V2, its dynamic range is not good enough for Q VNA measurement (using loosely -coupled sniffer coil). The dip is too small for 3db Q measurement method.

author: coppercone2
author_rank: Super Contributor
timestamp: February 19, 2021, 02:51:57 am
content: what do you think about using those ferrite slabs from the induction cooktop. i can cut them all to a uniform length of 2.5 inches with little effort with a diamond saw a i believe to make something along a 4 inch diameter. they are like 5mm thickI would be wary about cheap Q measuring equipment BTW.https://www.prc68.com/I/Qmeters.htmlI don't know much about good Q measurement though. The impedance analyzer is something I cannot afford. I find the TS-617C/U interesting

author: regenfreak
author_rank: Contributor
timestamp: February 19, 2021, 04:22:16 pm
content: The ferrite materials have different frequency characteristics depending on chemical compositions. My giant ferrite sleeve uses manganese-zinc ferrite materials which is commonly used for MW frequencies.They checked the cheap Mr Gao's Q meter against the gold standard HP4342 Q meter; i think it is about 20 to 30 % difference in readings.You can read about the magical Nckel-manganese R40C1 ferrite. It has blown my mind away; it is nothing short of spectacular.http://theradioboard.com/rb/viewtopic.php?f=2&t=7058&p=67909&hilit=2000Q#p67909To prove that the super ferrite sleeve is working, they really need to have quantitative measurements like Q measurements, antenna gain at particular frequencies etc. The biggest the Q is not necessarily the better the antenna. I think the cross-section area, length and length-to-diameter ratio is important. The science behind ferrite properties at different frequencies is very complex. I have looked up a few research papers on the subject. It is not my cup of tea.

author: coppercone2
author_rank: Super Contributor
timestamp: February 19, 2021, 08:38:32 pm
content: any hunches though?, it does seem like a fun and easy project so long I setup the diamond saw, a hassle in the winter as you can imagine