SolderSmoke Podcast

[@wxfreak]

Glad you are back! I love having the podcast on KZbin!

[@dolphus333]

Great to see you all on video for the podcast! I tuned over to here after hearing you on the HRWB episode Bill. As far as blogs as repositories of information, the post that generates the majority of traffic to my blog is a decade old post about deriving the divergence of a vector field in cylindrical coordinates. Apparently, it's an oldie, but a goodie :)

[@Northern-Rambler]

Brilliant guys, love the podcasts. Thanks for putting them out on KZbin too!

[@TheArtofEngineering]

Thanks Pete for the choke winding info (2.5 mH). I just tried winding one …. Got to 800 uH and gave up!!! Great info 73

[@grahamogle6332]

First time watching the podcast on here. Another interesting session. As you were saying about the podcast and blog being a repository of knowledge, I was just reading some articles from 2017 and 2018. It's a goldmine of usefulness. Agree with the comments about scratch building vs kit building and I've found that laying out circuits prior to getting pcbs made, really makes me understand what the circuit and every component does.

[@jampskan5690]

Pete has so much knowledge, I have to play at 3/4ths speed just so It can somewhat soak in to my brain!

[@migalito1955]

I agree, scratch build over kit build. Here is the issue I initially ran into regarding building the high school direct conversion receiver & it scared me off because it takes a lot of time to build one & an ambiguity in the schematic can lead to massive disappointment. Specifically, what I am referring to is the portion of the 40 meter band pass filter shown on the full schematic. In blue print just below the filter it seems to indicate inductors L12 & L13 are 3.0 micro henries with the following attributes, 5:26 turns #26 on T50-6. Immediately above this the drawing shows L12 & L13 where the symbol micro without henries is indicated and for L12 it's 0.58 micro-what & for L13 it's 3.02 micro-what. I can overlook that henries was omitted in listing on the schematic the complete inductance attribute for L12 & L13. I can not overlook that one piece of information describes L12 & L13 as each being 3.0 micro henries & the other bit of information seems to imply L12 is 0.58 micro henries & L13 is 3.02 micro henries. I am sure each one of you know what the proper data is for these inductors but for me it is entirely ambiguous. While I greatly appreciate your efforts & I could not have done better I just can't risk building something based on plans that seem to have a few bugs unless someone has the time to answer the prospective questions that may arise.

[@kk4das122]

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

[@migalito1955]

@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.

[@TheArtofEngineering]

Doug never made an SSB because CW is better… 😂. No tears when people insult Morse (other than tears of laughter). Horses for courses! I have the cockatoo problem too…. They make my vertical into a loop …. Whilst I hurl abuse and beer cans at them! They are little gangsters!!! Love this podcast congrats on 20 years…. and twenty more 🙏.

[@davidwheaton2405]

Love the Podcast guys! Keep um coming. Bill, what CCI amp are you building?

[@soldersmoke]

It is the AN762 140 watt version.

[@KQ4AOP]

Wasn’t DeMaw an editor and heavy contributor to the ARRL Handbook for many years? Were there any transistor-based SSB schematics in those? It might not have been his but he may have been in a role where he blessed the publication and may have even tested the design. If no one finds anything directly written by him, that might be the closest thing.

[@soldersmoke]

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.

[@KQ4AOP]

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.

[@KQ4AOP]

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

[@bendunselman]

For a moment I read the title as 'fake wives'.

[@G7VFY]

RF Burns can take a long time to heal, and are very painful. G7VFY

[@groovethaang]

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