Source for IF transformer assortments - Page 1
Forum section: electronics / rf-microwave

author: Dan Moos
author_rank: Frequent Contributor
timestamp: January 14, 2017, 04:28:27 pm
content: I am experimenting building radios, and would like to have an assortment of those little color coded IF transformers that come in the little square metal cans.I was wondering if there was a source for some sort of kit that covers the most common ones.Part of my trouble is that there seems to be very little info out there on the things that would tell me what to order if I wanted to assemble such an assortment myself. The few I already have are unmarked other than the color code. I don't know the turns ratio, the inductance, or the value of the little capacitor in any of them. Thus, I don't really know what to search for on mouser.Any thoughts?Sent from my E6830 using Tapatalk

author: kerrsmith
author_rank: Regular Contributor
timestamp: January 14, 2017, 05:33:52 pm
content: I often build superhetrodyne receivers and use the following IF transformers:42IF100-RC42IF101-RC42IF102-RC42IF103-RCThe first one is usually used in the oscillator part of the radio and the last three are used in the tuned circuits. These can all be purchased on Mouser - just do a search for the codes shown above and you will get the relevant part.Another way to get them (and a radio as well) is to get a radio kit such as the following from Banggood or AliExpress, they are all very cheap and work well:This is an AM radio and the simplest one I tried and has two tuned stages:http://www.banggood.com/9018-2AM-AM-Radio-Electronic-Kit-Electronic-DIY-Learning-Kit-p-946169.html?p=2D100314686672015046This is also an AM radio but is slightly more complex with three tuned stages:http://www.banggood.com/Seven-AM-Radio-Electronic-DIY-Kit-Electronic-Learning-Kit-p-946167.html?p=2D100314686672015046This is an FM radio that uses a CD2003GP IC to do all the work:http://www.banggood.com/DIY-FM-Radio-Kit-Electronic-Learning-Suite-p-1017325.html?p=2D100314686672015046I have built all the above (and more - kits are fun) and have had great success with them. Once you get to see how the radios work you can create your own designs using ideas from the different versions as a start - the kits all come with circuit diagrams so you can see which IF transformer goes where so you can then experiment with your own designs.

author: Dan Moos
author_rank: Frequent Contributor
timestamp: January 14, 2017, 08:11:31 pm
content: Quote from: kerrsmith on January 14, 2017, 05:33:52 pmI just finished building the AM portion of an excellent AM/FM kit from Elenco. Worked well, and was well documented. Thanks for the list of transformers. That helps a lot.I have been surprised at how little detailed info there seems to be out there on what was a staple of the hobby thirty years ago.Sent from my E6830 using Tapatalk

author: Paul Rose
author_rank: Regular Contributor
timestamp: January 14, 2017, 09:00:52 pm
content: 2nd vote for mouser.42IF100-RC Red Oscillator42IF101-RC 455kHz Yellow 1st IF42IF102-RC 455kHz White 2nd IF42IF103-RC 455kHz Black 3rd IFThe 42IF100-RC will be listed at mouser as if it was 796kHz IF, but it is really the oscillator coil.These are made by xicon.I built the 2nd of Dan's links ( "Seven AM Radio Electronic DIY Kit", but off of e-bay ) over the christmas break. I just used the parts and built it on top of an unetched copper clad PCB screwed down to a pine board, and gave it to my dad for christmas. I superglued down small pads of PCB material that I sliced off on a shear to create insulated islands for the parts. No problems, but the instructions are in Chinese, and it was fun figuring out which color transformer went whereWas able to align the IF stages, oscillator and antenna trimmers using a Rigol arb. waveform generator.

author: kerrsmith
author_rank: Regular Contributor
timestamp: January 14, 2017, 10:29:25 pm
content: Yes, the Seven AM Radio Electronic DIY Kit was a fun build - I initially scanned in the instructions and used Google to translate them (I was just curious what they said as there was a of of text).The only issue I had (after confirming the order of the IF transformers using the translation and Bangood's user feedback and images) was that the instructions said 'do not adjust the IF transformers' as they were pre aligned - for me this was not the case. After some time trouble shooting when I did not get so much as a hiss out of the speaker I de-soldered them and did an initial align by manually feeding a signal in to them at 455kHz from my signal generator and peaked them all up. I could have done this without de-soldering them but I wanted to make sure they all worked and would actually peak to the correct frequency just to be sure. The radio worked instantly once they were back on the board.I have another kit from AliExpress on the way, it is an AM / FM one - I am quite excited to get it. The last FM one I built (see previous comment) works really well and the built in clock seems to keep very good time. Getting the LCD screen attached was a little tricky as it used a very thin sheet of plastic with conductive tracks that goes between the screen and the PCB tracks (a kind of zebra strip I guess) but the rest of the build was fine.

author: Paul Rose
author_rank: Regular Contributor
timestamp: January 15, 2017, 03:25:38 am
content: Quote from: kerrsmith on January 14, 2017, 10:29:25 pmI had the "benefit" of not being able to read the instructions, so I assumed mine were unaligned.I built mine starting from the audio amp working backward, testing each stage. Once I had the last ( my first ) IF, I lightly coupled in a modulated 465kHz and adjusted for peak audio. I did the same as I completed the next two, re-tweaking the stages already done. The hardest part was the oscillator inductor and oscillator trim cap. I used a very small cap to couple some oscillator output into my scope, and used the frequency measurement feature to set the oscillator range, tuning the red coil to set the low end, and trim cap to set the high end, and going back and repeating about 6 times.I would have assumed 455kHz, but the instructions said 465kHz. Could have been a typo, but it will tune up fine either way.To get the antenna trimmer to peak, I had to slide the antenna coil all the way to the "left" end of the ferrite stick.I didn't notice the more expensive Elenco until after I was done. I downloaded the Elenco instructions. The theory, stage by stage test, and final alignment instructions are fantastic. I would recommend downloading and reading the Elenco manual even if you don't buy their kit.