After School Stem based on FM radio kit - Page 1
Forum section: electronics / beginners

author: watchmaker
author_rank: Unknown
timestamp: February 28, 2025, 07:16:26 pm
content: I have teamed up with a US Ham with the top license to offer an after school Stem program with 6 participants. I am figuring 2 hours per session with the number and frequency of sessions TBD. I will, of course be his teachingassistant.But I am the instigator. I spent the morning identifying prospective kts that will lead to a successful outcome and provide opportunities to follow the signal through the ckt. Marvin (my partner) is an accomplished Python programmer and has built a rig that can communicate from NH to the Antarctic on 3 watts (only exchanging digital data of course, no voice or cw).So we can give an overview on not only how everything from cellphones to bluetooth is a radio, but can also can an overview of how Arduino can be used.The kits under review run from $18 USD (IC based) to $50 USD (Discrete/IF based) and provide some (or much) soldering practice.The target population is 8th/9th graders who are taking algebra or trig. One objective is to show how math can be truly useful without teaching the actual math. Just an overview.We will be working with the High School and Middle School to select the students and figure out realistic expectation.So I have two questions.Do YOU have any suggestions for a FM radio kit to look at or, more importantly exclude. I am automatically excluding anything on aliexpress under $20.Second, if you haveexperiencewith this kind of thing, what is your advice.THANKS!!

author: Grandchuck
author_rank: Super Contributor
timestamp: February 28, 2025, 07:51:47 pm
content: Why an FM radio and a ham colleague?Just curious

author: janoc
author_rank: Super Contributor
timestamp: February 28, 2025, 08:16:48 pm
content: Quote from: watchmaker on February 28, 2025, 07:16:26 pmWhy? Are you looking to spend as much money as you can - or looking for something that can be sensibly built and the kids can actually take home without breaking a bank?What kind of receiver do you expect them to build in 2h sessions? You will be glad if you teach them to solder acceptably in that amount of time.I have made a simple kit using RDA5807 for a similar target group at our hackerspace. You can make it as simple as it gets, using the undocumented test mode of that IC where it only needs a few buttons for control, some passives, a pair of earbuds and 2 AA cells. Or you can make it more advanced, with an MCU, LCD and a stereo amplifier, if you want. That IC even supports RDS and I2S output if you want to make it very advanced. The kits on AliExpress are pretty much all variants of this. Those radios work fine, probably on par with any cheap FM radio.But keep in mind that 8 graders with no experience, in 2 hours where you will spend some time explaining the theory and which end of the iron to grab will not be able build a big kit. So keep your expectations reasonable and rather err on the side of "too easy" than "too much". It is easier to explain some stuff extra than to run out of time assembling and debugging the inevitably non-working radios leading to frustrated kids.And forget about doing an FM receiver completely discrete - you will waste a ton of time and without equipment and experience you will never get it to work properly. All discrete (i.e. no ICs) FM receiver is a pretty non-trivial project even for very advanced builders. That's not suitable for such target group at all.If you want to teach basics of circuit theory and don't want "black boxes" in the form of ICs, build a simple line follower robot instead. There are kits on AliExpress but it is easy to design your own. The AliExpress kits all use a comparator like LM339. I have built this with a discrete Schmitt trigger + darlington to drive one of those cheap plastic gear motors ("TT" motor). Build it twice to drive two motors, use a PCB as the chassis of the robot, use simple reflective light barrier sensors (TCRT5000) and it runs from 2 AAs no issues. There you can go nuts explaining how the circuit works and the kids can learn to use multimeter and basic troubleshooting when something inevitably won't work right. Again, this is a project that was built in a similar setting successfully. Similar projects that were popular many years ago before Arduinos and such were the "cybernetic tortoise/cat/ladybug" - all similar robots, usually chasing a light source (torch) and avoiding obstacles.Ideally you want a kit that can be built and debugged in stages. So no large PCB with a ton of components that need to be soldered for several hours, then it doesn't work and nobody has a clue how to fix it. E.g. the robot can be built with the motors + darlingtons first, test that, when it works build the Schmitt trigger, test it, works, add the sensors, test and adjust, as required.If you have more time - e.g. 4-5 2h sessions with one group, you can try something like a direct conversion receiver for shortwave (SSB/CW). This project was specifically designed for school kids:https://hackaday.com/2025/01/15/a-direct-conversion-receiver-anyone-can-build/It is much more hands-on than just assembling a kit, though, because coils need to be wound, there is no pre-made PCB, some tweaking/debugging is expected during assembly, etc.I would also recommend to go all through-hole, so easy to solder. While SMD can be done with kids (we did it with 7-8 year old ones), it is much easier when they need to focus on one thing at a time rather than having to figure out how to get the iron tip to the joint together with the solder wire and simultaneously trying to hold the tiny part in tweezers in their non-dominant hand without having it shoot across the room, never to be seen again. Some can do it but many will struggle. It is better to teach them to solder properly first instead of having them to learn multiple things at once.

author: watchmaker
author_rank: Unknown
timestamp: February 28, 2025, 10:11:15 pm
content: Janoc,Thank you. Why FM? Because the kits are well developed a this point and have high probability of success. Plus they can use it; there are many commercial FM stations here from Manchester, Boston and Maine. Plus we can use it to explain that many devices they use are radios.Why a highly competent Ham operator? Because he knows his RF and electronic fundamentals much better than I. And he is here and willing.I appreciate the time you took for second post and I am going to mull it over tonite.THANKS!!

author: janoc
author_rank: Super Contributor
timestamp: February 28, 2025, 10:15:51 pm
content: Quote from: watchmaker on February 28, 2025, 10:11:15 pmMy question wasn't "why FM" but why are you dismissing anything cheaper than 20 bucks on AliExpress. Expensive != better here.

author: watchmaker
author_rank: Unknown
timestamp: February 28, 2025, 10:36:51 pm
content: Got it.I looked at a sample of those kits. Most are AM which is not relevant today, and I was not impressed with the reviews. If you have a kit I should look at, please suggest it. I am also concerned about the "cool factor"; is it something they can show to their friends.

author: janoc
author_rank: Super Contributor
timestamp: February 28, 2025, 10:50:06 pm
content: No specific recommendations but these kits are all FM radios with the RDA5807 I was talking about:https://de.aliexpress.com/item/1005008181314943.htmlhttps://de.aliexpress.com/item/1005007619443784.htmlhttps://de.aliexpress.com/item/1005008143499253.htmlhttps://de.aliexpress.com/item/1005008048804247.htmlThere are many variants of these around. You can spend a lot more money on these but all you will get is more expensive components slapped together. It will be still the same cheap and basic radio.

author: bdunham7
author_rank: Super Contributor
timestamp: February 28, 2025, 10:50:18 pm
content: I got my nephew an FM radio kit and unfortunately he only learned about soldering, following instructions and what the various components look like. This kit used an all-in-on COB FM radio chip IC so there was no opportunity to learn anything about how FM radio or radio receivers in general actually work. It also was not a very good radio.If you want a "cool looking" kit I'd recommend this, although they still won't learn RF receiver fundamentals:https://www.amazon.com/ISolderStore-Electronic-Firefly-Module-Thanksgiving/dp/B0BMVY9TZKIf you actually want to have them learn about tuning, local oscillators, mixing and detection perhaps this would be better:https://www.amazon.com/Elenco-Radio-Kit-Combines-Transistors/dp/B008515U1UAnd I'm not sure why you think AM radio is less relevant than FM in this context. They're still broadcasting all over the place. AM radios can be used to demonstrate various odd things as well because they pick up all sorts of weird noise and interference.

author: janoc
author_rank: Super Contributor
timestamp: February 28, 2025, 10:57:32 pm
content: Quote from: bdunham7 on February 28, 2025, 10:50:18 pmI am not sure how you would hope to assemble, debug and align this kit with a bunch of 8 graders that have never done anything like that before and possibly without suitable test equipment. And try to fit in some theoretical explanations about electricity, how transistors works, what an oscillator is, filter, mixer amplifier ... In 2 hours, to boot.That's just completely unrealistic. That would need multiple such sessions and still would likely be a stretch to build an AM/FM superhet with complete beginners.

author: shabaz
author_rank: Frequent Contributor
timestamp: February 28, 2025, 11:09:59 pm
content: This AM/FM kit took several sessions, and needs supervision:After realizing that kids were actually quickly comfortable with SMD (again with supervision), I created my own "kit" (I'm not selling it, it's a free project for anyone who wants it, to order the PCB and parts themselves). It uses the typical Silicon Labs radio chip that is tuned with a potentiometer (so no need for tuning caps etc). Total parts cost is circa $25.This project is quick to assemble, since there are not a lot of parts, and almost guaranteed to work first time since there are no adjustments/trimming.

author: watchmaker
author_rank: Unknown
timestamp: March 01, 2025, 12:12:41 am
content: THANK YOU ALL!I will be printing this thread on Monday and share it with Marv, my partner.

author: bdunham7
author_rank: Super Contributor
timestamp: March 01, 2025, 12:42:47 am
content: Quote from: janoc on February 28, 2025, 10:57:32 pmI didn't read in there that there was only one session nor that they were necessarily absolute beginners. But sure, the Elenco kit is stretch for most--but not all!-- 8th graders. That's why I suggested two options. But with the first and most like it, there will be effectively NO relevant discussion of theory or math.

author: watchmaker
author_rank: Unknown
timestamp: March 01, 2025, 12:46:18 am
content: Correct. We are thinking 2 times per week; no. of weeks TBD with consultation of the school teachers (very small rural district that needs after school programs for students and ways to expand the horizons of students. Why I am thinking 8/9th graders.)AS for AM, only thing here is religious and political stuff. Not my cup of tea.

author: Brumby
author_rank: Unknown
timestamp: March 01, 2025, 01:31:01 am
content: Quote from: bdunham7 on February 28, 2025, 10:50:18 pmKeep this in mind if you want to venture into the realm of interference, crosstalk and all that jazz. It's a big wide wonderful world of EM radiation out there - intentional or otherwise!!

author: Sensorcat
author_rank: Regular Contributor
timestamp: March 01, 2025, 01:45:37 am
content: I like the idea very much and it's very good that you plan to offer something for the kids at your place. Actually, I thought about doing something like that also. But so far only volunteered at a repair cafe. Still having a job to do.Things that come to my mind:Depending on how used you are to work with kids, the challenge is to keep their attention high. Reward (in their metric!) must follow effort quickly.What do you want to teach, such that it is more than a soldering club?Electronics is abstract, and you need math for more than tinkering around. I wonder if the radio kit is a case study that offers a good reward-to-effort-ratio and a good learning-to-effort-ratio.Anecdote: When I was 12, I boldly walked into the local ham radio club to attend the course they offend to prepare for getting the ham license. I never forget the face of the instructor when, 3rd lesson or so, I raised my hand and asked what 'sin' means in these equations...There are lots of kits made for learning STEM stuff with robotics. Since mechanics is more accessible, that makes a lot of sense. As a team with your ham friend, you can cover mechanics + electronics.Having built a radio enables you to listen to the radio, something the youth does not do anymore, because internet. Having built a robot lets you play with the robot endlessly by programming it to solve all tasks you can imagine. And there is no 'app' that can do that! OTOH, their beloved smartphone can connect to the robot by wifi, bluetooth or the like. Endless opportunities for working on hard- and software to adapt the robot to new tasks. An open-end project.I hope you will report about the experience here!Good luck!

author: Brumby
author_rank: Unknown
timestamp: March 01, 2025, 02:03:47 am
content: Quote from: Sensorcat on March 01, 2025, 01:45:37 amThis is a direction you should really consider (IMHO). It is a big area of interest at this time. You can also build "battle bots" of all sorts of sizes - and that will appeal to many younger minds that seem to enjoydestructioncompetition.There are justso manyavenues one can explore under the banner of "Electronics". It might be an idea to ask the ones who really get involved what things are of interest to them ... and, perhaps, see if there is a path along this journey that could include one or more of those subjects.However, as these are early days, baby steps for the moment....Quote from: Sensorcat on March 01, 2025, 01:45:37 amThis is a trait of the world as it is today. When I was in high school, waiting a month for information was not unusual. These days, waiting for a minute is grounds for walking away.QuoteDitto!

author: watchmaker
author_rank: Unknown
timestamp: March 01, 2025, 11:05:25 am
content: I have started the proposal and lesson plans. Comments?

author: janoc
author_rank: Super Contributor
timestamp: March 01, 2025, 11:48:45 am
content: Quote from: watchmaker on March 01, 2025, 11:05:25 amYou will also need at least a multimeter for the students to be able to check for shorts and measure voltages. Any cheapie will do but it is not really negotiable. You don't need to have the kids keep them but they need to be available during work. There is also flux missing - common problem. Add a flux pen to your resources.We have transport cases for these workshops, where each case contains one complete workstation. Their content is (from memory):- Soldering iron + stand (cheap mains powered but regulated "firestick" - make sure to get reasonably sized tip for these!)- Brass wool for cleaning the iron- Spool of solder- Flux pen- A sheet of thin plywood to work on without damaging the table surface. Sheet of cardboard or, if you want to be fancy, those silicone work mats, will do too.Don't usethe self-healing cutting mats because they are not heat resistant.- Side cutters- Needlenose pliers- Normal pliers- Tweezers- Solder sucker- Desoldering braid- 3rd-hand with a magnifier (one of those cheap crocodile clip ones)- Multimeter (again a cheapie)- Small gooseneck lamp that can be clipped on the desk to provide extra light where needed (a lot of places we do workshops in have surprisingly poor lighting)- Lead-forming tool for resistors, etc. (those "staircase" plastic blocks you wrap the resistors leads over to bend them at a precise distance)This is provided by us, the kids don't need to bring their own or get to keep the tools. They do get to keep their projects.Not sure how do you hope show "processing of FM signal through the radio" using a scope. If you use an IC-based radio, then the scope won't show anything on the RF/antenna side and out of the other side you get audio already. And discrete components FM radio is not a project I would contemplate with children like this, as described above. It is just way too complex, even for very experienced builders with decent test equipment.If you want to show AC signal processing, build something like an audio amplifier, maybe with tone control - then you can demonstrate the effects using a scope and probe the signals after each stage to demonstrate amplification. So ideally a small discrete A, AB or B class amp, not a black box integrated one.You also need to dedicate time to troubleshooting and debugging - in my experience with projects like this, the kids were able to assemble the kits fairly quickly. But then good 40-50% of the time was spent troubleshooting shorts, poor soldering, components soldered in backwards, wrong components being used, occasionally something got fried and needed finding and replacing.On that note - do budget for at least 20% more kits and material than you think you will need. Things do get broken and lost and you will need to replace them on the fly so that the kids can continue working. And sometimes even the adults that come with their children want to build stuff. So having extras is vital.

author: watchmaker
author_rank: Unknown
timestamp: March 01, 2025, 12:06:32 pm
content: Of course, we will order samples before we commit, but here is one example of what I have in mind:https://www.aliexpress.us/item/3256806951382897.html?

author: janoc
author_rank: Super Contributor
timestamp: March 01, 2025, 12:20:36 pm
content: Quote from: watchmaker on March 01, 2025, 12:06:32 pmUh don't. That's a terrible idea. Do you really want to order a mains powered iron from Aliexpress for kids to work with? With who knows what quality insulation and build? What do you think you are going to get for those not even 2 bucks here?? That iron is also obviously not earthed due to the 2 prong plug - so very very unsafe and unlikely to meet any electrical codes.You were outright rejecting kits under $20 above as not good enough - and here you are planning to buy something that could kill you and start a fire for kids to use for not even 2 dollars? Seriously?Buy this stuff locally. It will be more expensive but certainly will meet at least minimal standards that it won't kill you or one of the kids outright. That is one thing youdon't wantto skimp on. If for nothing else then for your own sake - realize that if anything happens, you are going to be legally liable. That's pretty much a guaranteed way to prison.

author: janoc
author_rank: Super Contributor
timestamp: March 01, 2025, 12:59:37 pm
content: One more tip - you may want to consider using lead-free solder and not leaded. Not because it is easier to use (it isn't, even though it is possible to get decent lead-free today) but because parents tend to panic when they learn you are working with something poisonous - and you may get trouble (including legal).It is dumb but when you are working with others and especially children you need to constantly think you are with one foot in jail. School teachers can certainly relate here. That's why the seemingly ridiculous and over the top safety precautions - nobody wants to get prosecuted for causing bodily harm by negligence whenever the little Johnny or Jenny cuts or burns their finger.You may want to also consider the parents signing a waiver/consent before their kids could participate - exactly for these CYA reasons. Check with your lawyer how to do that/whether it is necessary where you are.I also saw you had eye protection on your list - good idea.

author: watchmaker
author_rank: Unknown
timestamp: March 01, 2025, 03:34:37 pm
content: Happily, all liability will be covered by the Town. I have worked with those under 18 for 20 years and used to train my trail workers about working with under 18s until I decided it simply was not worth the risk. You never know how the kid is loaded or even their parents who may be there. I never let a worker leave the group with an under 18 unless there was a witness who is not the parent.I have been background checked at least 4 times as part of my Wilderness First Responder activities (another place fraught with risk for the naive).Had a friend who was a ranked fencer and also taught. A classmate of my daughter was involved with a social worker who "recovered" a memory of the fencer abusing the girl. Charges were dropped 2 years later but it cost him plenty of cash and NO ONE offered an apology or to make him whole.It did not ruin his life, but it certainly changed his trajectory.In the US, everyone (cop, prosecutor ,judge, defendant's attorney) get paid no matter the outcome. But the poor schmuck is left at leat $20K poorer. Anyone wonder why so many innocent people plead guilty?

author: janoc
author_rank: Super Contributor
timestamp: March 01, 2025, 04:44:10 pm
content: Quote from: watchmaker on March 01, 2025, 03:34:37 pmThat's insane.

author: watchmaker
author_rank: Unknown
timestamp: March 01, 2025, 05:24:34 pm
content: It goes a long way to explain why the disadvantaged are overrepresented in prisons. Not a political statement, just an observation.

author: BillyO
author_rank: Super Contributor
timestamp: March 01, 2025, 05:59:18 pm
content: Have you seen this one?https://www.amazon.com/Elenco-FM-88K-FM-Radio-Kit/dp/B004YHZE0GInexpensive and lots of soldering and some interesting components. I think the SMD part is already mounted.Or this version here comes with the soldering iron and other tools for $2 more.https://www.amazon.com/WEmake-Soldering-Cutters-Glasses-Project/dp/B01JA8B4U2

author: bdunham7
author_rank: Super Contributor
timestamp: March 01, 2025, 06:09:10 pm
content: Quote from: BillyO on March 01, 2025, 05:59:18 pmThat's the exact one I got for my nephew. I can't recommend it as it isn't a very good radio, doesn't have a display indicating what frequency you are tuned to and can only be tuned by pressing the scan button IIRC. It was easy to put together, but really wasn't very interesting IMO.

author: shabaz
author_rank: Frequent Contributor
timestamp: March 01, 2025, 06:24:26 pm
content: Since ham radio embraces a lot more than RF and may well be the first encounter with any sort of electronics, perhaps it doesn't specifically need to be an RF project; it could be a radio building-block, or, anything comms-related.The photo shows a simple audio amp (happy to dump the detail into GitHub if desired, so anyone can build it, it's very basic) that would be very quick to assemble, and no trimming necessary. It could be a kind of field telephone or intercom. I think it could be fun literally using it in the field with a load of cheap speaker wire or whatever, and still be integrated into a radio sort of curriculum if desired as a building-block of a typical broadcast receiver.The parts cost for such circuits is extremely low (the trimmer resistor could be omitted to further lower cost), and all parts are jellybean.This particular circuit wasn't intended as an intercom, it had another purpose, but still produces audio with an electret mic element (there's one resistor on the underside to power the mic).As another example, the Forrest Mims books contain optical transmission/reception circuits, which again are comms-related and could be fun.

author: RoGeorge
author_rank: Super Contributor
timestamp: March 01, 2025, 06:38:45 pm
content: Maybe it's better to start with lead-free from the beginning, because everything now is lead-free. For a newcomer it will be just as hard (or as easy) to learn how to solder, no matter it's lead or lead-free solder. Otherwise they might have to re-learn soldering when moving to Pb-free.

author: janoc
author_rank: Super Contributor
timestamp: March 01, 2025, 09:59:02 pm
content: Quote from: BillyO on March 01, 2025, 05:59:18 pmYay for another non-earthed unregulated firestick. What do you think you are buying for that price? It is even worse than the $1.5 AliExpress iron above. The AliExpress one at least uses somewhat sensible tip type instead of the "sharpened nail" fastened by a grub screw this has. Excellent choice if you want someone to get hurt.

author: BillyO
author_rank: Super Contributor
timestamp: March 01, 2025, 10:08:51 pm
content: Quote from: janoc on March 01, 2025, 09:59:02 pmYou mean like the one I bought from RS back in 1975 that is still working, was made in China and never killed anyone?

author: janoc
author_rank: Super Contributor
timestamp: March 01, 2025, 10:13:19 pm
content: Quote from: BillyO on March 01, 2025, 10:08:51 pmExcept that one from RS was at least checked to comply with some minimal standards in force at a time. Here you are getting the cheapest piece of crap imaginable from some random fly-by-night seller on Amazon directly importing stuff from China. I don't understand why do you think your experience from 50 years ago is related in any way to this product.And yay, you want the OP to give this to school kids. I guess you have zero idea about liability should this one not be that well constructed like that one you got 50 years ago. I am sure the lawyers will be very happy to hear that you have led the kids use an iron than doesn't comply with electrical codes - it is free money!If you really want to use this kind of cheap junk, then at least buy them from Sparkfun - properly earthed and Sparkfun is doing at least the minimum in order to not sell unsafe or dangerous products.If you really really really want to use a crap iron like this, then at least buy this:https://www.sparkfun.com/soldering-iron-30w-us-110v.htmlThis is already much better, regulated and has higher power:https://www.sparkfun.com/soldering-iron-60w-adjustable-temperature.htmlAnd here is an entire toolkit:https://www.sparkfun.com/sparkfun-beginner-tool-kit-tol-22265.html

author: BillyO
author_rank: Super Contributor
timestamp: March 01, 2025, 10:17:58 pm
content: Quote from: janoc on March 01, 2025, 10:13:19 pmExcept that Elenco are a US company that has been around since I can remember (60 years or more), so are likely selling stuff that is certified for use in the US.

author: janoc
author_rank: Super Contributor
timestamp: March 01, 2025, 10:21:58 pm
content: Quote from: BillyO on March 01, 2025, 10:17:58 pmIt certainly isn't or isn't anymore. There is no way how an iron with exposed metal barrel without earth (has only 2 prong plug, so it cannot be earthed and it certainly isn't doubly-insulated) is going to satisfy any kind of electrical code in force or pass any sort of safety testing.

author: BillyO
author_rank: Super Contributor
timestamp: March 01, 2025, 10:28:38 pm
content: Quote from: janoc on March 01, 2025, 10:21:58 pmQuoteSure, we'll go with whatever you say. And I'll give you the last word..

author: janoc
author_rank: Super Contributor
timestamp: March 01, 2025, 10:30:55 pm
content: Quote from: BillyO on March 01, 2025, 10:28:38 pmShow me the FCC certification of that iron.Thenwe can talk. That something is being sold doesn't mean it is safe, certified or satisfies codes in force.

author: bdunham7
author_rank: Super Contributor
timestamp: March 02, 2025, 12:15:54 am
content: Quote from: janoc on March 01, 2025, 10:21:58 pmThey specifically market the iron as ETL certified, meeting UL-499 and a relevant Canadian requirement.https://shop.elenco.com/consumers/25w-soldering-iron-zd-200c-etl.htmlLinks to the ETL certification verification:https://ramuk.intertekconnect.com//webclients/its/dlp/products.nsf/vwSearch?SearchView&Query=FIELD%20ListHead%20Contains%20ZD-200C%20or%20FIELD%20CatCode%20Contains%20ZD-200C%20or%20FIELD%20Title%20Contains%20ZD-200C%20or%20FIELD%20ProductInformation%20Contains%20ZD-200C%20or%20FIELD%20ProductInfo%20Contains%20ZD-200C&SearchOrder=1&SearchMax=1000&SearchWV=FALSE&SearchThesaurus=FALSE&SearchFuzzy=FALSEThe iron uses a tip with a long back that goes down into the heater and is retained by a collar. I doubt it is all that great, but I don't think it is unsafe or any worse than any other cheap iron. They make two tips for it and unfortunately have chosen to include the conical one by default. You can see the ETL/Intertek sticker on the iron.

author: Smokey
author_rank: Super Contributor
timestamp: March 02, 2025, 03:34:37 am
content: Keep the frequency low and do a classAB audio amplifier. Tons of stuff to learn, lots of kits at all levels of integration from fully discrete to single ic, and they can use it to play music.Plus the test equipment requirements are way lower for audio stuff than RF. You could provide some inexpensive 1MHz bandwidth all in one scope/meter/function gen thing that would do the job fine for audio frequencies.ex. $36https://www.fnirsi.com/products/dso-510Just explaining the difference between frequent and time domain sounds like a nightmare for an 8th grader. I remember college kids that had a hard time driving a spectrum analyzer.

author: Smokey
author_rank: Super Contributor
timestamp: March 02, 2025, 03:40:58 am
content: Quote from: RoGeorge on March 01, 2025, 06:38:45 pmEverything..... Sold commercially into a rohs mandated industry.. nothing stopping you from prototyping with as much lead as you want. I don't use lead free until something goes to production, at which time I let my cm deal with that.Leaded solder is objectively easier to work with.

author: BillyO
author_rank: Super Contributor
timestamp: March 03, 2025, 03:28:04 pm
content: Quote from: bdunham7 on March 02, 2025, 12:15:54 amGood find.Now, if you really want to get an un-grounded iron with a sharpened nail held in with a grub-screw, you need only go as far as American Hakko.https://hakkousa.com/products/soldering/soldering-irons/red-503-soldering-iron.htmlAnd it will cost you as much as the entire Elenco kit!

author: edavid
author_rank: Super Contributor
timestamp: March 03, 2025, 03:58:06 pm
content: Quote from: watchmaker on March 01, 2025, 12:46:18 amThat's not such a problem if you also build a transmitter. I think that would be a good idea for FM also. Maybe that could be a whole class project, and then everyone builds their own receiver.An advantage of the AM band is that you can easily build transmitters and receivers on breadboards for class demos.

author: watchmaker
author_rank: Unknown
timestamp: March 13, 2025, 12:38:01 pm
content: OK. My ham operator colleague and I are both building the Elenco AM/FM kit. There are a lot of easter eggs! Measurement changes from RMS to P-P with no real warning or explanation. Measurement points are not identified in the written procedures, etc. Then there are poor quality parts (AM/FM switch, IC socket, counterfeit LM 386) etc.The parts issue is easy to overcome. The written instructions will be supplemented with written lab procedures. It is small wonder this kit has such a reputation.But there do appear to be design flaws. Hoping we can figure those out and correct. My partner we talking with another operator also using this kit in his STEM course. He finally decided the best end exercise was to do a hunt for a hidden transmitter.We all agree that AM is not worth it I do have on my bench an ALI discrete FM radio kit waiting for assembly. But I am still inclided to go with the devil I know.I have come to realize that student selection will be very important and we will be looking for traits that many adults do not possess:patience, self discipline, perseverance and ability to LISTEN.Still, I think we passed the point of no return. Showed the proposal to the town Librarian and the Director of Parks and Recreation. Both are very interested. Asked for a meeting with school district superintendent to give us a handshake with a middle school STME teacher to go over our expectations. My meeting request covered other issues (like how the district handles ICE access to school grounds and student records, notification a student's parent has been detained) as a Town representative.I have a original letter from a US govt office that tracked missing persons from 1958 (addressed to my mother). Sez yes, your spouse is alive and paying taxes but because of privacy laws we can provide no additional information.How far we have come in 60 years! So it goes. (And yes, I do understand the child support issues.)

author: BradC
author_rank: Super Contributor
timestamp: March 13, 2025, 01:13:54 pm
content: I started an after school electronics program in year 6 (1985). I was lucky enough to continue this through high school. I also joined the school "radio club" where we were taught by an old crusty HAM and spoke to people far and wide. My most cherished memory was the day they set up a time with NASA and we had about 10 minutes to communicate with the space shuttle.I've been following the thread, and I just wanted to let you know that as a kid that was given that opportunity when I was at school, it led me places I never even considered going.As suggested up thread, if you are doing an FM receiver, do a transmitter also. Colin Mitchell at Talking Electronics designed a boat load of easy to build long range FM transmitters. They're as easy to build today as they were 35 years ago.Lucky kids to have such encouragement.

author: watchmaker
author_rank: Unknown
timestamp: March 13, 2025, 10:04:22 pm
content: OK. Two of us have completed the AM radio section. I copleted every test and adjustment with the results described in the manual.If I touch the coil with my left thumb, stand on my head and touch my nose with the big toe on my left foot, I get the same Boston station my partner gets.Every other radio I own gets at least the religious and political talkers on AM.All the IF stages seem perfect although the gain is not all that great. I am going to post the schematic in the RF subforum and see if anyone can improve the design. Why is it so hard to create a kit that can receive AM, let alone FM (oh my the gods help me when I get there).Time to watch the last installment of the youtube that does this kit.Sadly, it may still be our best option.

author: ahsrabrifat
author_rank: Regular Contributor
timestamp: March 15, 2025, 10:16:16 am
content: You can use Elenco AM/FM Radio Kit (AM/FM-108CK). It uses a combination of discrete and IC-based components.https://www.elenco.com/wp-content/uploads/2017/10/AMFM-108CK_low-res-2.pdf

author: watchmaker
author_rank: Unknown
timestamp: March 19, 2025, 12:19:36 pm
content: As promised, both of us completed the Elenco AM/FM kit. Given that we are using this for instructional purposes, I went thru the instructions line by line.It is obvious these kit instructions have been cut and pasted over the years by people who were grudgingly assigned to the task. Many minor errors, some very misleading (wrong test points) and some pretty egregious (after aligning the FM stage by stage while building, telling the builder to reset all xformers to the top before final realignment; telling those using equipment to set FM modulation deviation to 1kHZ and not 22.5kHz).It is small wonder that this kit has a bad rep. In the end we both produced decent radios once we identified the faulty alignment procedures. The kit results in an FM radio of very acceptable performance.So,we will use this kit and I will write specific lab procedures for each alignment step.In talking with people at Elenco, they acknowledged they suspected our findings were the case. I told them I would share the edits and lab procedures (and ask for a credit in the revised manual.).We are getting a quote on 8 kits, and spare ckt boards, IF xformers, tuner, coils.We will replace the AM/FM switch, IC sockets, sub a real LM 386, and provide a supply of reisistors, ecaps, transistors etc so that when supplied parts are out of range we can provide substitutes. I found gain was below spec on some stages until I replaced the transistor, and some resistors used for voltage dividers were too far out. Same with ecaps. Most of the ceramics were good as were most of the resistors.We will also leave the alternative discrete audio amp for the end if we have time. This is not central to the program. Mine had an oscillation issue we need to resolve.But the goal is to have the participants create a successful build that they can be proud to show off. So I want to keep the values as close to nominal as possible to eliminate sources of error.Once done, this kit receives all the stations as my 1969 Panasonic RF 930 and 1989 Nak TM1/2. The primary limiting factor is the 2 inch speaker which is rectified by a USB speaker such as a JBL or such. LM386 is not bad.We will provide our personal DMMs which hopefully cannot be damaged by the participants. We will also provide two scopes and signal generators that will be used only under our direct supervision. But they will do the hookups.We did this using the same tools we provisionally selected to provide the builders; soldering kit, eyepro, sidecutters, tweezer kit, needle nose, alligator clips, ckt board holder (all from Ali). We expect the total lab fee should be $100 plus or minus.We will provide two rolls of good desolder braid. I hate those plastic solder suckers and the traces do not like the Hako.Main job hazards are eye injury and burns, possibly asthma issues. I am a certified first responder so that is covered. We just need water/ice available.I also think I may include a statement of participant responsibilities and acknowledgements that both student and a parent sign (only work on battery operated stuff, not using soldering iron as instructed can result in burns, etc). Then we have the normal liability issues such as injury liability and child abuse (which in our case would be unfounded but cost should not be on us). Hence the need to be under the auspices of the school district or Parks Dept. May suggest we become dollar a year employees.Sad to have to think about this stuff, but I have seen too much crap at my age. And better to know where the landmines are.Meet with the District Superintendent on Friday.