On the SolderSmoke blog you will find at least 43 postings about the Mythbuster. But to answer your question, look at this one: soldersmoke.blogspot.com/2021/06/the-stubborn-myth-about-usb-and-lsb.html You see, for decades hams were taught that if you have a filter at 9 Mhz and a VFO running around 5.2 MHz, you will end up with USB on 20 meter and LSB on 75 (with no shift in the carrier osc/BFO). This, they claimed, was WHY hams transmit on LSB below 10 MHz and USB above 10 MHz. A nice story, but not true. In fact, this arrangment doesn't produce the convenient LSB/USB split. That's the Myth. I busted it by showing that if you reverse the filter and VFO frequencies you WILL get LSB on 75 and USB on 20. I built the rig this way to bust the myth. Hence the Mythbuster.

@@justinelliott3529 yes!

Lots of details in the links in the KZbin video description.

And Happy Birthday Pete!

I think if someone did this and shared the blog posts or videos, Bill would share it on his blog and maybe even mention it on the podcast. Manhattan is so easy when it comes to correcting mistakes. The Charlie Morris style looks interesting. As for 3D printing, there is the PTO, a 9-volt battery holder, knobs for the PTO screw, and maybe a wire wrap for the simple antenna. Walls for the rig possibly…

That would be a different project then! Our idea with the high school class was that, just once, they should build something from scratch and as close to the metal as they can. No computers, no CAD programs, just learn the analog circuits and assemble by hand. Perfectly understandable if that is not your thing. You may be more interested in the Vienna Wireless Society's Makers group project that I mentioned. We are going to be building an SDR receiver front end starting with a block diagram, developing the schematic and PCB layout in Kicad, ordering boards and assembling them. The purpose of that project is to learn the entire workflow and to end and give our group some experience with surface mount construction.

That's cool, maybe the SDR project is a better fit for me.

Oh, and thanks for the readout, I still think valve is a better description of an analogue device because you can vary the flow of electrons the same way you can vary the flow of water with a hosepipe tap 😁 Clint

Daniel: We have on the internet YEARS of schematics, pictures, videos, diagrams and tutorials on this receiver. Just take a look at the SolderSmoke blog. Or: hackaday.io/project/190327-high-schoolers-build-a-radio-receiver Or: www.remmepark.com/circuit6040/SolderSmoke-DCR/SolderSmoke-DCR.html#AUDIO_AMP In this video, I just hoped to show what the receiver was capable of. To bad you found it so lacking in what you were looking for. Perhaps the links above, or maybe Google would help. Bill

Lots of information in the KZbin video description.

No entiendo. Me parece que puedes escuchar a muchas cosas. De acuerdo?

Thanks Peter. I think it sounds fine -- its transfer through the internet may be making it sound bad. I did check the audio bandpass characteristics and in fact changed the emitter bypass caps from 47 uF to 470 uF for better audio. It helped a lot. As for the hiss, again this may be an internet/KZbin thing. I always check to see if the hiss is coming from the receiver or from the universe. In this case, it is the universe! Band noise. When I disconnect the antenna, the hiss disappears. Thanks for the recommendations, but our goal here was to develop a VERY simple receiver. So we don't have any feedback, we don't have a push pull amp at the final etc. These things might have been nice, but they would have added complexity, and that was something that we were (and are!) trying to avoid. We would be honored if the Wizard of Melbourne (you!) built one of these receivers (please first build it our way -- mods can come later ) and then did a video on it. 73 Bill

John: I never really looked at this, but I measured about 40 milliamps, with a small speaker attached. 73 Bill

You remind me of when I was winding coils on pieces of 2X4's. 60 years latter my lab is full of HP, Agilent, Keithley, and Fluke gear. And now, with transceivers of all vintages on my shelves and desks I'm back to building gear on scraps of wood, and having a ball. But admittedly it's now a lot easier to tune the circuits than back when I did it all by ear. :)

@@johnwest7993 Cheers. I am only recently getting back into it at 58. But I am more Logic and Audio inclined than RF. I'm living with chronic heart failure and back on a tight budget. You should see 12V 21W array of 10 globes I made up as a cheap load tester lol I had a lot of fun making that :) > I had fun on plywood. For smaller projects I would dig up some old kitchen cabinet laminate which worked well. > These days I have packs of breadboard and veraboard, and use acrylic for cases. But I still like that classic wood grain feel :) I was looking at that speaker box and getting all excited lol

😅😅😅😅

Oh, we know, we know! Great that you are going to build it. Send progress pictures!

Well, have you looked at the build instructions for the BP filter on our project web site? hackaday.io/project/190327-high-schoolers-build-a-radio-receiver or on the QRP Labs web site? qrp-labs.com/images/bpfkit/bpf3.pdf Is that enough, or do you need more info? 73 Bill

​@@soldersmokeI only have a cell phone to use with 4G based service because I retired to a very remote section of the Catskill mountains. Getting resource material here can be difficult. I found that the instructions on Hackaday regarding the filter essentially are cryptic enough for one never having built this style of receiver that actually being shown an example is for me needed to guarantee no mistakes. My only experience with band pass filters comes from simple coils & variable capacitors as used in the regenerative receivers I have built. Yours due to toroids and impedance matching is a type I have never seen or assembled. I searched around & I found a video Pete produced. The link is pasted below. Is this an exact example of what your device uses ??? If so, problem solved. www.google.com/search?q=how+to+construct+a+40+meter+band+pass+filter&oq=how+to+construct+a+40+meter+band+pass+filter&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIHCAEQIRigATIHCAIQIRigATIHCAMQIRigATIHCAQQIRifBTIHCAUQIRifBdIBCTI0NDYwajFqN6gCFLACAQ&client=ms-android-tracfone-us-rvc3&sourceid=chrome-mobile&ie=UTF-8#fpstate=ive&vld=cid:77da4a6d,vid:BjqvvzI1YLg,st:0

Is this the filter???! www.google.com/search?q=how+to+construct+a+40+meter+band+pass+filter&oq=how+to+construct+a+40+meter+band+pass+filter&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIHCAEQIRigATIHCAIQIRigATIHCAMQIRigATIHCAQQIRifBTIHCAUQIRifBdIBCTI0NDYwajFqN6gCFLACAQ&client=ms-android-tracfone-us-rvc3&sourceid=chrome-mobile&ie=UTF-8#fpstate=ive&vld=cid:77da4a6d,vid:BjqvvzI1YLg,st:0

It is the AN762 140 watt version.

Like when I touched the anodes (450V) of a QQVO6-40A on a 2m TX in 1978. I was thrown across the shack, but had the burn marks for a couple of years. 73. G0OER

There is also Solid State Design for the Radio Amateur, which has SSB transceivers (IIRC). But it is never clear which of those were DeMaw's. He was quite prolific, but I never recall seeing any articles by him talking about SSB transceivers. Also, he consistently got the sideband inversion thing wrong, which indicates that he may not have actually built SSB rigs.

Maybe here? May 1989 QST, p 25 - it starts “Must everything you design be for CW operation?” This is also in QRP Classics from 1990.

It is a SSB receiver. Maybe you want to find a transceiver.

Migalito, thanks for taking on the 40 meter direct conversion receiver project. As I mentioned in the podcast, learning to read and understand schematics comes with experience and practice. The band pass filter consists of two parallel tuned LC circuits coupled by the small 10pF capacitor across the middle. This is a classic "double tuned" BPF that is well documented in books including Solid State Design for the Radio Amateur. Each of the LC circuits consists of a 3.02uH inductor in parallel with a 164pF capacitor. You get the 3.02uH with approximately 26 windings on a T50-6 core. The 5 turn .056uH windings are there to make a good match to 50 ohms in and out of the filter. These values don't need to be exact, but should to be within about 5-10% for the filter to work well. The schematic you reference is drawn in LtSpice. Since the unit of measure of inductors is always Henries, the H is optional on the schematic. The same is true with the R for resistance and the F for Farads. You often will not see the H, F or R on the schematic because you already will know the units of measure. The blue text is simply a comment we inserted to assist in reading the schematic. We give you the number of turns so you don't have to figure it out. The 3.0 is a typo, likely mis-transcribed from my pencil drawing - you can ignore it. Here is a hint though - published schematics often have errors, some minor, some major, so its important to try to understand the circuit. Even with extensive proof reading and having builders test the circuits we often still find small errors. That said - the DCR schematcis are clean and you can rely on them. Keep building and share your success with us! 73, Dean KK4DAS Here is a link to the schematic for anyone to follow along: drive.google.com/file/d/18Yk6DhgPUTlGKFMlj2GYI-QooMJlSzWf/view?usp=drive_link

@kk4das122 Thanks, I'll give it a go now that I know what you are indicating. I was considering just working out the band pass filter myself to establish how to build it but did not want to step deeply into a project that for me might be even more ambiguous because indeed these projects take many hours. As a retired mathematician I do now recognize the EE community does things differently such as approximate non linear relations with linear functions which when first encountered with respect to Bipolar transistors caused a major head scratching because they had omitted for ease of calculation they were aiming for a close enough rather than an actual model of the transistor's characteristics. Also, you have to remember the aim was to create a beginner's project, one designed for high school students, with the goal of creating interest in the subject. For one that has previously built direct conversion receivers I am sure they could have derived what to construct from the given symbolic representation. However, like a function written in C++ where a preface in the form of a comment indicating what is expected as input & what can be expected as output is of utmost importance for downstream users so as to avoid their spending large amounts of time reverse engineering the function; I'd say clear representation that did not rely on pre knowledge of the object being built best fits the aim. I am also reasonably sure all the successful high school students had to be shown what was intended by the schematic and it's commentary, but aside from this one cryptic area of the schematic everything else offered no problems for me. The thing I want to avoid is building another project from the pages of QRP or some other magazine only to find out years later and after hours spent building the project that as published it could not work because of an error in the plans. Had you not explained the intent of the schematic, relative to the band pass filter, I doubt I would pursue it which more or less lets the air out of the aim of bringing people into the hobby.