Jaycar L15 toroid - Page 1
Forum section: electronics / rf-microwave

author: A.Z.
author_rank: Super Contributor
timestamp: October 26, 2020, 08:12:26 am
content: Hello everybody, I was thinking to build a UnUn for a randomwire using this designhttps://vk6ysf.com/unun_9-1_v2.htmmy problem is that I'd prefer using an Amidon or FairRite core and can't figure out the material corresponding to that "L15" one, I've tried searching the intertubes and from the very scarce informations I found, it seems that the L15 should be more or less matching the #61 material, does someone here have some pointer to a "material equivalence" table or the like and/or confirm that the L15 is, in effect, equivalent to #61 ?

author: madires
author_rank: Super Contributor
timestamp: October 26, 2020, 10:04:45 am
content: I've built one with an Amidon FT140-77 (0.5-30MHz) for SWL. I can't say much about its performance since I don't have an NVA. But so far it works fine for me.

author: A.Z.
author_rank: Super Contributor
timestamp: October 26, 2020, 10:24:47 am
content: Thank you "madires", and yes, I already used #43 and #73 in the past and they worked pretty well, but I was curious to know the equivalent material for that "L15" used by Jaycar

author: madires
author_rank: Super Contributor
timestamp: October 26, 2020, 10:49:12 am
content: L15's datasheet states 0.1-2 MHz "practical frequency" and a µ of 1000. Resonant frequency for Amidon #77 is 1 kHz - 2 MHz and µ is 2000. Seems to be the best match.

author: A.Z.
author_rank: Super Contributor
timestamp: October 26, 2020, 10:52:38 am
content: Thank you again, so #77 is the equivalent, I'll try that !!

author: profdc9
author_rank: Frequent Contributor
timestamp: October 26, 2020, 11:03:41 am
content: If you have a NanoVNA, take your ferrite or and put a couple of turns around it and measure the impedance of the inductor made this way at port 0. Keep the leads short. Generally, you look at the frequency where the resistance equals the reactance (R=X). If the frequency at which this happens is <2 MHz, its a manganese-zinc ferrite core, suitable for MF use (<5 MHz). If this is greater than 2 MHz, it is a nickel-zinc core suitable for MF/HF use.Another cruder way to ascertain the type of core is to measure the resistance of the core when you touch the core with two multimeter probes a few millimeters apart. If the resistance is very high (>10 Mohm), it is NiZn, and if its less than 1 Mohm, it probably is MnZn. However, sometimes coatings or paint is added to the ferrite that insulates the ferrite, so it may look like a high resistance material (NiZn) when it is a lower resistance material (MnZn).You can check out my NanoVNA presentation that includes how to measuring balunshttps://drive.google.com/file/d/1nIkENrhJBO--Bj0yU6yIQrfH-gIgBDqV/view?usp=sharing

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 26, 2020, 01:36:07 pm
content: You could've linked... anything?I guess this is the datasheet they provide:https://www.jaycar.us/medias/sys_master/images/images/9437376577566/LO1238-dataSheetMain.pdfBut if you were looking at a different product with a different datasheet, I have no idea.The modest tan δ, lowish µ, low Tc and Bmax, and high ρ, sound like a NiZn material, with a cutoff in the low MHz -- #43 is most similar.Tim

author: A.Z.
author_rank: Super Contributor
timestamp: October 26, 2020, 02:16:33 pm
content: Sorry for not linking the datasheet, and thanks for the infos, but at this point I'm wondering if it's a #43 or a #77, although, given the frequency response of that UnUn I tend to believe that it may be more similar to a #43; thanks again (and no, I don't have a VNA, otherwise I won't be here asking for help)See, I'm going to help a friend putting up a random wire antenna, and I wanted a well working UnUn; since in a past I built this onehttps://vk6ysf.com/balun_9-1.htmbut using an FT240-43 instead of the T200-2 which isn't good as a wideband transformer, I thought that the "V2" could be fine as the previous one (except for the core) was, that's why I asked about that L15 equivalence; but given the replies, I think I'll stick with an FT240-43 which already served well (the other randoms had SWR less than 1.5 on all bands from 80 to 10 meters and the radiation efficiency was confirmed by a lot of contacts made with 100W max)Thank you again

author: cdev
author_rank: Super Contributor
timestamp: October 28, 2020, 03:42:34 pm
content: Would you be able to upload it here?Google is blocking me, claiming that I am doing something, they wont tell me what, that violates their terms of service, even though I am not. I have a totally vanilla, generic setup.I suspect its because I've expressed (true) opinions that they seem to not like.Quote from: profdc9 on October 26, 2020, 11:03:41 amAlso, I just found this.. Its from an old (2007) PDF.Image attached. May not be super useful, since it doesn't have jaycar info. But judging by the sites name, maybe some more info could be found there.Seems like the newer page ishttps://www.vkham.com/resources/reference-info/ferromagnetic-informationLooks promising.

author: cdev
author_rank: Super Contributor
timestamp: October 28, 2020, 03:55:53 pm
content: Quote from: A.Z. on October 26, 2020, 02:16:33 pmCommon generic ferrite split beads sometimes work really well for making ununs (or baluns) -they seem to be very good at this.But you wind them differently, instead of going around it like you would a toroid you wind it through the middle, keeping the wire inside the cores as much as possible, the effect is you need fewer turns and shorter wire, I suspect this may be a very good way to do it, especially considering the cost. I'm sure it depends a lot on the material, but somebody might easily get lucky if it works well for RFI in a given frequency range there is a decent chance it might work well as a unun or balun. Can't beat the price.Three wires twisted together makes a good 9:1 unun. Just a few inches of wire is needed. (Less turns than with a ring core)You could also make a balun pretty easily. Try to use identical cores from the same batch. If you have four you could make a balun like the switchable elecraft balun (BL-2) which can do both 1:1 and 4:1 by switching the output from series to parallelYou'd ideally use four identical cores, and you need a DPDT switch. Make with two binocular cores that balun is really efficient. It can be grounded in the middle. Take care to make it symmetrical.But even if you just have a single split core you can make a decent working unun, wrap three wires together in a twisted pair like way. If you are using ethernet wire I wouldn't try to wrap it super tight unless you are using thicker wire. Slightly less tight but neat. I did it with two cores and that works quite well. Its just soldered to a BNC female connector and it currently has two alligator clips to connect to antenna and ground.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: October 28, 2020, 04:10:18 pm
content: if it's turning bout matching the core properties, I'd suggest Fairrite material 43; with a ui=850 it's the closest to 1000; on the other side, for frequencies <4MHz I'd rather go with material 77on the other hand; in reality there is always never a use for a 9:1 unun; its usage is more an urban legend with very little physical facts on its side. let's face it: most of our antennas in the lower shortwave and mediumwave spectrum have, due to their low altitude above ground, a very low real component with a high Xc - so they are far away from 450 ohms real impedance

author: cdev
author_rank: Super Contributor
timestamp: October 28, 2020, 04:14:30 pm
content: You're likely working with much much better antennas than I am.For receive with the kinds of receivers I use a basic 9:1 unun always makes a dramatic improvement in receive, which may be due to the large reduction in noise. A larger impedance ratio can sometimes work even better, that's basically empirical data, but it does.Assuming the shield is grounded presto, then the input wire in the unun becomes markedly sensitive to proximity to anything that might be able to act as an antenna.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: October 28, 2020, 04:22:04 pm
content: well, you just start to widely open the door to the discussion about so called 'quiet antennas'to oversimplify a little, I could say, a 'quieter antenna' is a worse antenna in any way.of course for reception only, all that matters is the S/N ratiooften not even the antenna is the problem of bad reception, but the feedline and common mode currents on it, they don't only appear when sending, but also when receivingso, even if the antenna is placed away from qrm, you're going to receive it anyway by the feedline

author: cdev
author_rank: Super Contributor
timestamp: October 28, 2020, 04:29:13 pm
content: There are a couple of situations where it makes a huge difference. One is magnetic loops where the antenna is also a pre-selector that wipes off frequency signals off the map while delivering very high voltage signals at the tuned frequency, so strong that the receiver is overloaded and needs an attenuator. Another situation where impedance matching might be useful is when you have no handy 100 foot vertical wires but do havetreeshandy.Tree properly matched can become your vertical antenna and one with a fairly low angle of radiation although on transmit, some power might be lost heating it (Even when I get set up to transmit and have a rig capable of doing so I would not use them for transmitting directly, but I think it would be possible with some kind of "gamma match", But no nails for transmitting, I love my trees.) In the past it worked so well for receive in fact I think I am going to try doing that again right now. Because they are pretty tall. Too tall for me to get my wires over them easily. Plus its safer as far as lightning to not have the actual wire up in the tree. The tree I am thinking of has already been hit and scarred by lightning. I wish that I had a small portable receiver I could bring outside.Quote from: HB9EVI on October 28, 2020, 04:22:04 pm

author: HB9EVI
author_rank: Frequent Contributor
timestamp: October 28, 2020, 04:48:24 pm
content: well, even a magnetic loop is not only receiving the magnetic field component; its advantage is the narrow passband since it acts as an LC resonant circuit tuned on the receiving frequency.you can also build a wideband active magnetic loop, where the loop is basically a short circuit with an real component of a few Ohms.sure, even my Inverted L is mostly acting as a vertical antenne with a capacitive toploading, but it doesn't chance anything on the low real radiation resistance which is no more than 10-20 ohms + the high Xc which has to be compensated by a imaginary component. You cannot compensate the Xc of such an antenna with a 9:1 unun, if your antennas real feedpoint component is only a few ohms

author: cdev
author_rank: Super Contributor
timestamp: October 28, 2020, 05:30:56 pm
content: The way Ive been told to do it is to use the unun to get into a ballpark area and then the antenna tuner has less of a problem matching them. Its rare that somebody doesnt need a tuner. But for receiving who cares. It will help but the biggest help comes from the unun.I think it is the unun because - let me give an example, I have a softrock here, with a piece of coax and a BNC connector with two alligator clips. If I ground the shield onto my radiator and put my finger near the BNC, I dont receive much until I touch it, esecially at lower frequencies.But if instead of just the BNC I add a small 9:1 unun, the flying lead that's the high impedance input starts receiving stuff even though its just a few inches long, even in MW. And if I hold it, I become a surprisingly decent antenna. Any kind of wire at all, even just 2 or 3 meters will work. Much better than just using the 50 ohm input. Much less noise, especially. Especially if the ground is semi decent.Try it.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: October 28, 2020, 05:57:30 pm
content: yea, I heard already so many tales about the 9:1 'magic' unun together with the onboard tuner. to be received like that is for most the undeniable proof of concept. The problem is actually to not radiate some RF at all; people just don't realize, that most of the power remains in the tuning elements and the unun core; it's not much more than a dummy load. that QRP works, is well known, but so many hams think they are qro while they are more like qrp.another big topic is the confusion between protective earth, grounding and RF earth. Using gutters or radiators as RF earth almost a guarantee to get qrm and rfi/tvi into the system.most of us live on sites with poor RF earth, like sandy/rocky ground; the aim of RF earth like a radial system around a vertical is to reduce earth loss and improve the effective radiated RF over the low feedpoint resistance.and no, I'm rather using my active antenna system with a Whip and active magnetic loops for RX

author: mag_therm
author_rank: Frequent Contributor
timestamp: October 29, 2020, 08:22:48 pm
content: I am trying a Fair rite 75 mix with 12 T on antenna side and 2 by 4T on tuner side.This tuner has a very low impedance when tuned to frequency.The random wire is 13.3 metre long.First image is an approximation of reactance variation with frequency.Second image is with the tuner on to CHU Canada 7850 kHz.The signal (right-most) is at about S8 (-79 bBm)The QRN noise floor is about S5 (-97 dBm)Just below , ( to the left) spread over 50 kHz, is a QRM "thing" pulsing a comb spaced about 2 kHz every 200 millisec.

author: A.Z.
author_rank: Super Contributor
timestamp: October 30, 2020, 11:35:34 am
content: Quote from: mag_therm on October 29, 2020, 08:22:48 pmA random is a cheap, easy and pretty decent antenna, but it's far from being a quiet one, if you want to try a "crazy antenna" (RX ONLY!), here's what I came out time ago after much fiddling; I started with a regular linear loaded dipole (also known as "cobra") fed with window line and a 4:1 balun, the antenna worked well enough, but I kept fiddling with it (again used it for RX ONLY), so made a change at time and checked the result, the final config was the following: pick some length (as much as you can) of 3-conductors wire (flat or round) and cut it in half to have the two arms of your LLD (linear loaded dipole), connect the three wires of each arm in series and then connect the two wires (one from each arm) at center to a 9:1 balun (yes, as crazy as it may sound) and now try listening, I believe you'll be surprised

author: W4HBM
author_rank: Newbie
timestamp: November 13, 2021, 03:56:48 pm
content: In order for RF to go somewhere it needs to have current. If the current is all swimming around in a transformer(BalUn, UnUn, etc.), then it sure ain't going out into the neighborhood.The 9:1 and even the 49:1 ferrite toroid-core baluns are wonderful for receiving, SWLing, but not too good on Transmit.If you need to send, having two antennas is doable provided you protect the front ends of the receivers, and even two antennas (Rx2 & Phase Canceler Noise) just for receiving, hung in different azimuths are excellent.Using a small antenna tuner with L and C selections is perfect for insertion in the Unbalanced coaxial line from the BalUn.If you need to send, as started just before, a resonant half-wave dipole with appropriate matching BalUn is the bestway outward, and mostly we're talking 160, 80, 75, 40 and even 30 & 20 if you get the lengths right.So we gotta choose material for our new 9:1 or 49:1 now.The ferrite material, surprisingly is tantamount to the performance we seek. Even though many aficionadosgo by the Initial Permeability and the words of others praising MnZn or NiZn, the true "oomph" may be seen on the LO-1238 specs as 2500 Gauss with 20 Oe Coercive Force, and on the Fair-Rite 31 mix as 3600 Gauss with 34 Oe C-f.And it just so happens the LO toroid has a frequency ceiling of 3 Mhz and the 31 mix a ceiling of 300 Mhz.If I'm SWL'ing on 80 and 40 with an EFRWire using a BalUn would it not seem reasonable to go for the bestcoercive force since the incoming electromagnetic wave is the initial muscle? So 31 Mix is the winner in that lineup,but wait- There is competition! Fair-Rite 43 mix and 52 mix make for good low-F transformers, too.The best way to do an apple-and-orange comparison is to put up a good quarter or half wave wire and have itresonant to one or more WWV frequencies, like 2.5, 5.0, 10.0, 15.0, etc. Then build a temporary balun, insert it, and see what the signal report for any number of similar times-of-day reports. One or more different transformers will shinelike stars, and one or more will completely fall in the mud.A simple exercise, and a wonderful experiment.

author: A.Z.
author_rank: Super Contributor
timestamp: November 13, 2021, 04:05:41 pm
content: So, you are suggesting to throw all the calculations and VNA tests in the trash bin and do on the air tests, instead ? It doesn't seem so reliable to me, also since we have no control on propagation, but then, maybe I'm just an old fart.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 13, 2021, 07:06:48 pm
content: FYI, that LO-1238 appears to be NiZn, more or less comparable to Fair-Rite #43 and such (mu_i is a bit higher, but their tolerances do overlap). You can tell by the high resistivity and low Bsat. A physical test would be a streak test, should be brown; MnZn is black.Upper frequencies for transformers, are fairly irrelevant; under power it'll matter (heat!), but for receive, not a big deal. You're going for core impedance only; most any ferrite is going to be dominant resistive (so, causing insertion losses moreso than adding reactance) at high frequencies. This is above a few MHz for these materials, up to 10 or 100MHz for #67, #61 (and similar types). Up at such frequencies, the latter ferrites, and also powdered iron (Micrometals #1 or 2) or air core (or TL fractional-wave impedance transformers, and other distributed or resonant methods) are preferred.So, not really much need to be picky here. Concentrate on getting adequate radiation resistance (over losses, so that efficiency / noise floor is good) and good tuning (so SWR is low).Such high ratios (9, 49..) mean either electrically short, or anti-resonant, antennas. You won't get wide bandwidth, in either case, so expect to need a new tuner setting for each band you work. For a wideband or multiband antenna, you need a different design. Ultrawideband designs incorporate large elements with regular (self-similar scaled) structure, so that the antenna looks pretty much the same with respect to any wavelength; this is obviously most practical at high frequencies (log periodic, various horns and cones), and less practical at low frequencies (most of SW).Note that antiresonant antennas largely radiate through strays, such as imbalance in the feedline, elements, conductors in proximity, etc. The radiation pattern, feedline current (common mode) and impedance are very unpredictable here.Tim

author: A.Z.
author_rank: Super Contributor
timestamp: November 13, 2021, 07:48:31 pm
content: So.... where's the point ? I was asking for an L15 equivalent, and. I found it's more or less a. 43 in amidon catalog, fine with me