Chinese mass-produced versions of maker projects are already valuable members of my workbench team.
(Author’s Note: This is the “zero’th” part of what will be a three part series on printed circuit board milling. This article is where I decide on what milling machine to get and the reasoning behind it, so there is no actual PCB milling here. The point then? Document the purchase decision making process as it’s made, then look at the final results later and see where it went right or wrong.)
I never thought I’d say it, but Chinese “knock-offs” have really found their niche. I’m not being facetious – in all honesty there is actually something really wonderful that they are accomplishing. It all starts with someone on a maker’s web site like Instructables or mikrocontroller.net where someone comes up with a great little project. Like, say, for a multi-component “transistor” checker. Designers create these “open source” projects which are intended for everyone to enjoy, and they document everything and just release all the specs and design documents so that not only can anyone build it, but also anyone can improve on it. Sometimes, for the better projects, a whole community builds up around the project. Once that happens along comes some Chinese manufacturing company and they take those detailed instructions and mass produce a kit for it. Now, suddenly, not only are the specs available but now anyone can put it together for $15. Win/win/win. A win for the author, who finds that once anyone can build the project he designed the community really begins to thrive. A win for the consumer and the project community who get fantastic equipment at a fraction the traditional cost, and a win for the manufacturer who was incentivized to do all this by the low R&D cost and who makes some money selling the kits. This is just fantastic. Hardware manufacturers doing for maker projects what Red Hat and Ubuntu did for Linux.
I’ve taken advantage of this process a few times recently. What I’ve just discovered is that this phenomena has reached the wonderful world of the desktop CNC milling machine! I was aware of the many Chinese clones of 3D printer project kits, and had even played with the idea of getting one, but I hadn’t been aware until now that you could get a desktop sized budget CNC mill.
I finally found one! Now sitting on my shelf is a beautiful Drake TR-7A, serial number 12195, and I am in love. Welcome to the family!
My new Drake TR-7A – already a beloved part of my shack.
When I was conducting research for my initial HF radio purchase, I had narrowed down to the Heathkit SB-104A rather quickly. It is a beautiful radio itself. However, as I was researching it I found that the principal designer for it, Mike Elliot, went on to work for R. L. Drake and to design their TR-7. What I read was that the Drake TR-7 was what Mike Elliot had wanted the SB-104 to be.
SB-104A – is Mike Elliot’s prototype Drake TR-7A?
I couldn’t afford a Drake TR-7 at the time, nor were there any good options to buy a decent one anyway. And, honestly, I was content to go with the Heathkit. After all, one of my major purchase considerations was to get a radio I could tinker with. In fact I wanted to get a radio that was basically going to force me to tinker and learn (without going so far as to buy myself a problem). The SB-104A that I purchased was affordable, was (and is) itself a fantastic radio, and has given me ample opportunity to tinker and upgrade it. But I’ve always had in my head this thought: if I love my Heathkit, and the Drake TR-7 was what its designer had wanted that Heathkit to be, then what kind of radio is the TR-7?
I will be finding out!
A special thanks to Gary Follet, W0DVN (known also as “dukeshifi”) who sold me the radio. An excellent person to do business with.
My SB-104A has been on my workbench for the last week as I work on the talkback and the 60Hz line noise appearing on the transmit audio. I received a report that my transmit audio was almost unreadable due to the noise. I first thought it was bad filter capacitors on my power supply since I could see the 60Hz noise on the 13.8V power rail during transmit. It turns out I can see it there for two reasons:
- My shack has bad 60Hz EMI and poor radio shielding was letting that appear on my input audio.
- My output RF was appearing on my 13.8V rail because of the SB-104A’s well known talkback issue.
I decided to try my hand at both problems. Continue reading
So, as I wrote in my last post, I had taken my Heathkit SB-104A radio offline due to suspected power supply problems. Under load it appeared to be sending AC directly through to the radio. It turns out this wasn’t the case, that a couple of issues are at at work here:
- The SB-104(A) is prone to sending RF and the modulated audio signal back up the 13.8V rail. This “talkback”, as it’s known, is a well known SB-104A issue and is addressed in several QST articles.
- My “shack” has terrible, terrible, terrible AC noise and it’s obviously leaking into my radio. Which was then getting onto the 13.8V rail through the same mechanism the talkback audio was.
So, yes – it’s not my power supply after all. What’s particularly embarrassing is how long it took me to figure this out. I didn’t have anything handy on my bench with which to test the power supply under load (except for the radio itself which I wasn’t going to risk), so I pulled the filter capacitors out to test figuring they had to be the culprits. When it looked like they were good, puzzled, I began preparations to test every part of my power supply if need be to determine where the trouble lay. I was even writing a blog post about it – I was going to title it “combat troubleshooting”. My workbench, while increasingly well kitted, is woefully short of those odds and ends parts most old-time hams have which let them whip together pretty much any kind of test circuit they need at a moment’s notice. So I was going to do a bit of “combat troubleshooting” and (as Matt Damon said in a great movie recently) “science the shit” out of my power supply to work out where the problem was with a minimum of equipment.
That’s when it occurred to me, it should actually be quite easy to test my power supply under load – I don’t need load resistors, a few automobile headlight bulbs in parallel should be just the trick. And wouldn’t you know it, when I hooked them up to be the load, what did I see but a beautiful, stable, exactly 13.8 volt DC line without even a whisper of ripple.
Face, meet egg.
I’ve taken my HF radio, a Heathkit SB-104A, offline for now. I had noticed some 60Hz line hum through the speaker when transmitting, however I didn’t really think much of it. I just assumed the audio pre-amp was picking up some hum which was getting through. It wasn’t until I got an audio report from a QSO who said he could barely understand me over the 60Hz hum that I got concerned. If the audio circuit was picking up a little hum, I could live with that (at least until I got around to sorting it out). But to be told I could be barely understood over it, that was more serious.
The SB-104 uses several voltages internally. It is supplied with 13.8V from the power supply, which is then regulated down to 11V for most things, and 5V for some of the digital stuff. However, I remembered that the final amplifier used the 13.8V supply voltage straight – and if, under load, the power supply was letting some bad ripple in, then this would essentially modulate the output with that 60Hz ripple. Sure enough, putting my scope on the power supply output when it was under load by the radio showed a huge AC component. Ouch!! Continue reading
My 80m off-centre-fed dipole antenna has been up for a few days now. It’s up but I’m sort of shooting blind when it comes to knowing if I’ve got it right. I hate shooting blind. I had to make some educated guesses when building it, and with an off-centre-fed dipole you have not just the length but the feed point and balun to get right.
So, I’ve been looking at different antenna analyzer options. Most are pretty expensive. One that is both less expensive and which also seems to have a lot of promise not just as an analyzer, but as a general purpose piece of test equipment is the Fox Delta AAZ-0616 Antenna Analyzer. I have high hopes for its use as a sweep generator, and maybe (perhaps with a pair of them) as a poor man’s spectrum analyzer.
Mine is on order. More to come!
As of Mon, 4 Jul 2016, I became the proud owner of a new multiband off-center-fed dipole that should be resonant on most bands from 80m down. Is there a formal project document for it? No. Will there be, most definitely. I’m off the wagon more than I’m on it when it comes to keeping things documented. Does this means project management principles are failing me? I’ll have to give that some thought. At the moment, though, I’m too elated at finally being on the air for that to be a huge concern.
A big than-you to Kevin, N5DX, operating a net from N2QV’s station in New York state, who at 0144(Z) 7 Jul 2016 became my very first HF QSO.
iPHone vs Ham Radio: Let Mortal Kombat Begin!
A few years ago another blog writer wrote that “ham radio will never have the sex appeal of the iPhone”. The writer was using that statement as a base to opine that despite this (airquotes) fact (end airquotes) there are more new ham radio operators now than ever before. It’s true, there are more new ham radio operators now than ever. However, I don’t accept the premise that it’s in spite of anything. I don’t think the resurgence in amateur radio is despite its lack of sex appeal. It’s because of it’s sex appeal. If you are a ham radio operator, and you run into someone who thinks that an iPhone is sexier, then don’t be shy, call the guy out and challenge him to a sex appeal contest between your rig and his little toy.
In my last post, I talked about how I came to the idea of applying proper project management principles to my amateur radio hobby to add focus. It was a great idea, but I’d forgotten just how much leg work there is in proper project management. Mission statements, project definition documents, deliverable identification, scope of work documents, risk assessments… it goes on and on and that’s all stuff that happens before you even start work. I’ve re-learned that being a project manager is something like being a Catholic or a Mormon. There is always more you should do than you ever can do so you always feel guilty about missing something. I suspect that’s the way upper management gets more out of them. Any conscientious person in that role will flog himself trying to keep up. Now I don’t want my hobby to be like this. If all it is is a bunch of “you have to do this” tasks, I’ll never do it. So I’ve come up with a model that I think works, will help me focus my efforts, and will keep things fun. Continue reading
I have been a little unhappy with the progress I’ve made to date towards getting my ham shack operational. It’s not the lack of progress per se, which is to be expected given circumstances, but the haphazard nature of it. Things are happening in fits and starts and I have multiple things on the go at once. Maybe that too is only to be expected, considering I’m trying to shoehorn this hobby into an existing life. But I’ve been thinking I could benefit from some added focus so as to avoid spinning my wheels. Continue reading