Hack-A-Day has an interesting post about an FM Broadcast radio project. I took a look. The Github page has the schematics for the hardware. For me, the thing is, there is just not a lot there. It is a bunch of chips. The FM Tuner IC is the heart of the project. With that one you have to dig down to see that it is a digital processing chip:
All of the action -- all of the magic of radio -- is locked inside those little SMD chips. I suppose if you were skilled enough to write the software or to significantly modify it, you'd get closer to the experience of homebrew radio, but very few of us have those kinds of skills -- we just download the software, then struggle to get it into the chips.
And sure, you could struggle to solder those chips to a PC board, but really, why bother when 99% of the components are already inside the chips? You should just buy a board with the chips on them and with the software already loaded. There you have it: the store-bought appliance is really, really close to the supposedly homebrew receiver.
But hey, to each his own. This is a hobby and it is all for fun. I just think I have more fun with old-style, analog, discrete component HDRs. YMMV.
Posts
ReplyDeletewell said, and I agree.
It's probably a generational thing, but I'd argue that these days more people (tinkerers) are able to understand and modify the software of this project than the circuit of a Michigan Mighty Mite. And yes, YMMV
ReplyDeleteCrikey, I have difficulty deciphering the cryptic designations of the connections, let alone understanding the designated functions!
ReplyDeleteIt has no soul
ReplyDeleteThis takes all the fun out of homebrew!
ReplyDeleteThis is fine. You can solve problems in many ways. Sometimes the journey is important. Sometimes the destination. It’s still magic whichever way you solve it.
ReplyDeleteIt's a FM stereo broadcast radio reciever, yes.
ReplyDeleteYou will have very little control over the demodulation, like the controls are very limited.
If you want to change it, it's not much to access.
Not really a reprogramable reciever(SDR) to decode using random modes e.t.c.
How do you fix it when something goes wrong? Can you even find the parts and actually get them delivered?
ReplyDeleteI am currently on the hunt for a no-chip, all analog QRP transmitter. VXO, plug in crystals and LPFs. Nothing but CW, the original mofe!
Maybe it's time to add a new term to the lexicon: "home-built." To the extent it matters, it would be used to refer to rigs of this HaD sort, reserving "homebrew" for projects that . . . hmm, that's the problem: how to define it. It's the same difficulty Justice Potter Stewart had in addressing pornography in Jacobellis v. Ohio (1964). He couldn't define it, he said, "but I know it when I see it."
ReplyDeleteAll good points Bill and you know I agree. There is nothing as satisfying for me as looking into the details of a circuit and trying to understand how it works from first principles. I was reading last night about how to pull the frequency of a ceramic resonator VXO and it took me down the rabbit hole of oscillator circuits, crystal theory and on and on. Fun evening's reading. That said, a project like this little FM transmitter could be a gateway project for a tinkerer who wants to learn more. That's what happened to me when I bought the uBitx V 5.0 - it was a light assembly pseudo-kit - all of the components were on the board - just attach the controls and put it in a case. I was intimidated by even that - having to solder connections (after 35 years of not picking up a soldering iron) was challenging. I was so excited to get it on the air and so pleased with myself at having not destroyed it in the process. But, in the end I found that I didn't get what I wanted from it - which was an understanding of how radios really work, and it was ultimately unsatisfying. I bought a book on simple circuits you can build on a push-in prototype board - but after lighting an LED they author moved quickly ICs as well. Then I found SolderSmoke - built a Michigan Mighty Mite with a crystal mailed to me by N2CQR himself (thanks Bill) - for which my wife had to pay postage due - and haven't looked back. So, I have patience for the homebrew Wanna-Be's - and the Vienna Wireless Makers group has plenty of those - and they are amazed when they find out that they can actually build a rig from what looks like an undifferentiated pile of components!
ReplyDelete73 from St. Michaels
Dean
KK4DAS
I agree with you Bill. This design and schematic is very typical of how digital electrics is designed and drawn now-a-days (actually for quite a while). EEs really like it (I think, they keep doing it) and it is very "object oriented". Everything is interconnected by obscure designations. The chips are like "black boxes". No clue what is inside, therefore it is not possible to get a feel for what the circuit does by just looking at the schematic. many different chips share similar pinouts. They have obscure part number that are basically obsolete within a few months anyway. If I drew a schematic of a transceiver using this technique, each transistor would have it's on "block" with just a bunch of input and output connections. How boring can you get?!
ReplyDeleteAND...SMD is for robots, if you (a human mostly) want to home brew something, use parts you can actually see and handle with human hands.
So there.
Actually this "schematic" was drawn by someone that does not know how, or was never taught, how to draw a human readable schematic diagram.
ReplyDeleteOne reality that makes this issue--"homebrew" vs. some-other-kinda-thing--so difficult to pin down is that we're dealing with differences in *scale* rather than differences in *kind*. At the simplest level, every electronic component we use is an integration of smaller parts (electrodes, dielectrics, semiconductor materials, resistive materials, etc.) put together at various levels of complexity.
ReplyDeleteA beam pentode such as a 6L6 is a lot more complicated than the single-triode 6GK5. A 12AT7 integrates two triodes in the same tube. The little 6U8A integrates a triode with a pentode. In the solid-state sphere, there are almost thirty transistors (similar in characteristics to the 2N3904/2N3906) integrated in a 741 op amp chip, but upwards of 100K transistors in the MCU used in an Arduino Uno. These are certainly big differences in scale, but not of kind.
The form of the schematic shown in the HaD article is another example of difference of scale rather than kind. It also has a number of virtues. Right off the bat, it highlights circuit functions by actually boxing each one in. Some drawers of discrete-component circuits try to label functions such as VFO, IF amp, etc., but others leave it to the more experienced to figure out and to visually trace the sometimes-long and convoluted lines that represent interconnections. But more-traditional schematics have long used labels instead of actually-drawn lines to connect B+ (a commonly-used label), GND (in the form of a symbol), portions of circuits on separate pages, and otherwise separately-presented circuit segments. These labels abstract away actual wires or cables in the interest of clarity, though they might confuse the uninitiated just as the ones in the HaD schematic might. To be sure, the labeling used there is on a much larger *scale* than used in at typical multi-page schematic in a 1960s ARRL Handbook, but it's the same *kind* of thing.
Of course, the HaD schematic shows the use of off-the-rack modules that are complete systems in themselves. Plugging them together doesn't seem like much, though that's what many of us do using discrete components. Either we fish an old VFO, band-pass filter, or power supply out of the junque box, or we reuse segments of schematics we have already tried and tested (audio-amps, DBMs, IF amps) and integrate them into our circuits. We might take them off *our* racks, but they're still "off the rack" like the units HaD shows. Again, a difference in scale rather than kind.
Differences in kind are easy to judge, differences in scale not so much. I've said before, but it bears repeating: integrating whole systems is no more trivial than integrating individual components. "Just plugging them together" does not absolve the builder of the need to match supply voltage, signal levels, impedances, communication protocols, or to consider system architecture. Nor does one get to forget about noise and distortion figures, bandwidth, EMI/RFI concerns, or basic quality/reliability requirements. Of course, copying someone-else's integration, buying the modules, and just plugging them together doesn't require much thought and doesn't teach much, but neither does building something verbatim from a QST article (alas, necessarily from an old one).
Maybe a distinguishing feature of homebrewing, then, is how much thought and how much learning goes into a project? Oh, but wait . . . damnation, those are matters of scale, too! You know what? After all that, I give up! I'll have to live with uncertainty--again. Anyway, I have to get back to today's to-do list. I've decided I need to reread Pete's latest blog post on integrating an Arduino and Si5351 module with a nine-tube mixer, IF, and audio module he's built--chassis, point-to-point wiring, and all. Hey! I wonder why he doesn't seem to care about this homebrew issue? Maybe I'll find out in his post.
Todd K7TFC
Great comments. I guess for me, the threshold is where I start to lose touch with the signal flow in the IC: If I can still understand what is going on in there (not just inputs and outputs) I am comfortable using the device. So I am at ease using devices like the LM386 or the NE602. But for me, once we move into the microcontroller or CPU area -- where the transistor count goes far beyond our ability to think about signal flow -- I get uncomfortable. But again, this is a matter of personal preference in a hobby that is just supposed to be for fun. Whatever floats your boat! YMMV! 73 Bill
ReplyDeleteAmen for that...
ReplyDeleteIt's an FM stereo receiver with a ton of features. The schematic tells you only the interconnections, to understand more you have to go to the datasheet. At this point, even just reading the first page often tells you enough to make sense of it.
ReplyDeleteThe step here, I think, is to treat the IC as a functional black box. Just understand how to connect it, feed it, and clock it, and with a bit of experimenting, it should work. The key to a project using an I2C device like this is to find a trusted Arduino library for it, and some online accounts of other experimenters who have had success with it. If you can read the library functions, and the datasheet confirms that the device does what you want it to, then you have a chance.
For example, this device works down to 50MHz and supports 25kHz channel spacing. So could you make a 6m FM receiver with it? Probably not, because amateur FM is NBFM. Asking questions like these is at the heart of amateur homebrew repurposing. For example, did Infineon ever consider their IRF510 would make a serviceable 5 watt 15MHz RF amplifier? It was hams who discovered it's utility for RF.
We all stop digging into working out how something works at different levels of abstraction. The advantage of being able to work with black box ICs and use other people's libraries and designs is that we can do more complex projects more quickly and reliably. Standing on the steps laid down by others...
It's all good fun. I'm still as attracted by a two transistor MOPA CW rig as I ever was!
Paul VK3HN.