Where to source IF transformer sets? - Page 1
Forum section: electronics / rf-microwave

author: Yansi
author_rank: Super Contributor
timestamp: January 15, 2018, 01:37:56 am
content: Hi!Just a question out of interest, where to source IF transformers - I mean those with the screw on top one can turn to tune them. It would be nice to have a source of new ones for some decent homebrewing. I might have a few small project ideas where I could have a good use of those.Does anybody have experience sourcing those? Where can one buy these IF transformers for a reasonable price, like a $2 a piece a pop worst case?I have found that Mouser already have someXicon coils 42if1xx seriesfor a very nice price. However these are only the 455/10.7 IF transformers, none for oscillators or other frequencies unfortunately :/Thanks,Y.

author: chrisl
author_rank: Regular Contributor
timestamp: January 15, 2018, 01:54:30 am
content: What is the IF freq? and the BW?The listed ones are for the typical AM and FM bands.one's IF can be another's RF... ;-)Best,

author: Yansi
author_rank: Super Contributor
timestamp: January 15, 2018, 02:31:28 am
content: Question is as broad as it can be. These components seem to be almost unobtanium, so anything will be good to know about.Regarding the project I mentioned, anything in the range of up to about 30MHz.

author: David Hess
author_rank: Super Contributor
timestamp: January 15, 2018, 03:02:37 am
content: I have seen people use 10.7 IF transformers at other frequencies by replacing the built in resonating capacitor.

author: phenol
author_rank: Regular Contributor
timestamp: January 15, 2018, 04:01:13 am
content: Do they have to be transformers? Any reason why regular tuning slug coils won’t work?

author: medical-nerd
author_rank: Regular Contributor
timestamp: January 15, 2018, 10:08:00 am
content: HiyaCheck out the coils on this page:http://www.spectrumcomms.co.uk/Components.htm- he has a set of IF coils made as 10mm TOKO replacements - I have bought a number of these (lots as I will use them over the years!!)He is on ebay.co.uk as antonnaile-0 and the prices are very reasonable.I have no attachment to him other than buying a number of his IF coil sets and books: Technical for the Terrified bookswhich are a collection of his articles published in the UK magazine Practical Wireless.Cheers

author: Yansi
author_rank: Super Contributor
timestamp: January 15, 2018, 11:19:25 am
content: That is an interesting find, however the price is slightly over the edge of what is reasonable. A pack of 5 coils £4.60 plus £3.40 shipping. If I try adding more pieces, to reduce shipping cost, it is just doubled, trippled,... accordingly. £2 a piece is not reasonable, at least not for those of us who does not poop money yet.Also I would not like to be dependent on an ebay seller, that has very limited amounts available (it seems). I'd prefer something that could be repeatably sourced from a manufacturer.Like those on Mouser, however the frequency ranges there are not too much of a choice. You say replacing the resonance caps? Is that even possible with those small coils?

author: medical-nerd
author_rank: Regular Contributor
timestamp: January 15, 2018, 11:52:22 am
content: HiyaI share your concern regarding supply - so I stocked up on a range of coils from him. (went slightly mad and bought approx. 80 over few months....)Check the postage - he sells mixed sets of 10 on ebay and combines shipping costs.These are also available to buy from GQRP, for members - you can then add lots of interesting rf bits.....Over here the cost is reasonable for 10mm coils, since the commonly used TOKO coils from 70s/80s designs are upwards of £4 each plus postage.CheersCheers

author: GrahamC
author_rank: Contributor
timestamp: January 15, 2018, 01:00:14 pm
content: Yes indeed, these once very common transformers and coils are becoming more difficult to source and those that you do find can be on the expensive side.There are a few good sources and the link to Spectrum Communications is a good one. Minikits in Australia also sells some but has limited supplies.http://www.minikits.com.au/index.php?route=product/search&search=transformerOr, you can rewind them into whatever type of transformer or coil you need:http://www.carnut.info/star-parts/pcbs/toko-winding.htmhttp://www.qsl.net/g4usp/OZL%20Coils/OZL%20coils.htmA google search will return a few more such examples.A bit finicky work but with a good pair of tweezers, patience, and practice this is not too difficult to do. The 10mm square ones are the easiest to work on but the smaller sizes can also be easily modified.Another option already mentioned is to wind your own using small torroids but in that case you would need to use a small variable capacitor in your circuit for adjustment. I had a link to web site which had such an example but can't put my finger on it at the moment; I will post if I find it.cheers, Graham ve3gtc

author: Yansi
author_rank: Super Contributor
timestamp: January 15, 2018, 01:21:47 pm
content: I have also hoardered a lof of those older IFTs. But the 70s and 80s in our country looked quite different from the rest of the world. We have had really shit here, rest of the world was starting to have computers at home.Those old IFTs I have are unusable for any kind of modern designs. Unless I really want to stick with THT stuff (which in many examples I do not want to).Of course those larger ones, specifically those with the inner tuning slugs are totally easy to rewind, however many of those modern ones I have came across use an outer tuning ferrite shell and are fragile as a glass barbie and any attempt to disassemble those ended by breaking the ultra thin inner ferrite core.I may try to order a bunch of the coils from Mouser and see if they can be rewound without destruction happening. But I almost doubt it.

author: phenol
author_rank: Regular Contributor
timestamp: January 16, 2018, 04:35:35 am
content: https://store.comet.bg/Catalogue/Product/22715/i’v used these a lot and they lend themselves to disassembly really well. If i’m feeling lazy, i use small(or big where IMD matters) ferrite or iron powder toroids and trimmer caps. Q is almost always superior to what those canned coils can deliver.

author: Yansi
author_rank: Super Contributor
timestamp: January 16, 2018, 10:45:03 am
content: 0.23USD a pop... and that for real?Do they sell abroad? Bg... that is Bulgaria?Do you have experience buying other types of RF coils from them? Like the KT10 type they advertise here:https://store.comet.bg/download-file.php?id=662//EDIT: Did a bit of searching on that website. You found a gem, phenol! ... only if they sell and ship internationally of course. Need to figure that out.

author: phenol
author_rank: Regular Contributor
timestamp: January 16, 2018, 11:00:30 am
content: Yes, they are in Bulgaria. You can contact them and ask what their shipping policies are.The coils i've used have a ferrite shield cup and tuning slug.

author: bd139
author_rank: Super Contributor
timestamp: January 16, 2018, 11:05:44 am
content: If you must get them, then Spectrum Communications and JAB Electronic Components still sell them, for now.Just a personal opinion though: I hate the bloody things and I have 100% abandoned them on any design. If you look at the material from the 1960s/1970s from practical wireless etc you will see where this is heading to. A lot of the old projects were based on the old coils from Denco which seem to change hands now for silly money. Think £10-15 per coil (!). Also they aren't standard pitch on any boards which makes prototyping with them quite difficult, they are also very fragile and don't survive repetitive tweaking and are very difficult to dead bug withEvery single use case can be replaced with amidon cores which are dirt cheap, available nearly everywhere and have been for 30+ years. If you must tune or resonate a transformer, then use a little vishay trimmer cap or something. Avoidance is best though; most things can be done with W7ZOI/bitx style termination insensitive amplifiers, crystals, single wound amidon cores and basically avoiding anything to do with wretched IFT's. I think the only time I ever use a transformer is winding them for DBMs and that's only because I'm too cheap to buy an SBL-1 or something.Most of the Spectrum Comms stuff uses the IFTs because Tony spent years pumping articles out which need those parts. It's part of the business model. GQRP guys sell them as well BUT if you look at SPRAT there are very few examples of IFTs actually being used in any designs as they are complex and not fungible. You will instead find "any old shit lying around with wire spun around it".Have a look here for a relatively elegant design which avoids these problems:http://www.hfsignals.com/index.php/ubitx-circuit-description/

author: Yansi
author_rank: Super Contributor
timestamp: January 16, 2018, 11:24:15 am
content: Okay then, but where do you buy amidon cores? They are extremely expensive here. Like $1-2 for a 10mm iron powder toroid is quite a bad price I think.

author: phenol
author_rank: Regular Contributor
timestamp: January 16, 2018, 12:04:20 pm
content: Quote from: Yansi on January 16, 2018, 11:24:15 amyea, that's because they are made to look pretty.

author: bd139
author_rank: Super Contributor
timestamp: January 16, 2018, 12:29:17 pm
content: They're colour coded so you know what they are...They're really cheap here and they're not made here. I buy them in packs of 5 from GQRP club (have to be a member).Might be more expensive than cheap chinese cores but they are accurate and stable which means you can make repeatable circuits with them.You can always air cored. Air is cheap

author: Yansi
author_rank: Super Contributor
timestamp: January 16, 2018, 05:56:15 pm
content: But copper is not cheap though

author: bd139
author_rank: Super Contributor
timestamp: January 16, 2018, 06:00:35 pm
content: Everywhere on this planet there is a nice source of enamelled copper wire you don’t have to pay for. Just needs liberating from wall warts, old TVs and PC power supplies that have blown up.

author: phenol
author_rank: Regular Contributor
timestamp: January 16, 2018, 06:16:27 pm
content: out of curiosity—what are you going to make with those coils?

author: Yansi
author_rank: Super Contributor
timestamp: January 16, 2018, 10:20:48 pm
content: Quote from: Yansi on January 16, 2018, 05:56:15 pmbd139: Well... that was just statement of required amount of wire being much larger for air coilsI have no problem accessing a lot of different enamelled wires, including TEX wire. I work with power conversion and transformers a lot.phenol: Curiosity is always welcome! Nothing exact was on my mind when I was asking. Sometimes I feel a need to build some radio prototype of some sorts, sometimes working with peculiar radio ICs that require transformers for operation.. so why not get the proper ones, but in more modern shape and size. I have only available those very old ones, which are kind of big (on the other hand very easy to rewind and modify).I have briefly browsed on Aliexpress for RF toroidal cores. Definitely there are lots of them available. Would not classify them exactly as cheap, compared to the standard mix #s used in power conversion like #26, #52 <--- at least those I can source for a fair price from a local distributor.I have also a decent set of RF cores I have hoardered over the years, however the materials have very different coding style and getting proper datasheets for them is kind of complicated, as these have been only manufactured locally "back in those days". Sometimes even if you (think to) have the right datasheet, even simple measurements of the cores does not correlate to the datasheet very well. It is possible such large manufacturing deviations were present back then, but who really knows. I even don't know now or can't remember, if these are ferrites or iron powder. As our German colleagues would say: Keine Ahnung!