Whole Lot o' Crazy Stuff Goin' On!
Many years ago I got into searching for single-purpose ICs that would or could be used to make a decent radio. Just something to replace, say, all the tubes & shock-box parts in an old Hallicrafters S38 probably come off the factory floor when I was still in diapers.
I came across quite a few ICs, actually.
There's the TDA1072AT, which I will extrapolate on below.
The TDA1572 chip is the gussied up version of the '1076 with a separate IF output for whatever uses one might dream up.
There the TDA1083, which is everything you need for a receiver, including a small .25W audio amplifier. It's laid out a little weird but it looks like a promising trip. (I say looks like because I have ten of 'em and have yet to fiddle with a single one for any purpose at all. Limits.)
Then there are a handful of other ICs, most of 'em Sony chips, many of which are no longer available except in vast quantities from warehouses here and there in the Orient or wherever. Among these are the TCA440, which is a pretty neat little RF/OSC/MIX/IF chip for which the builder must provide a detector & AF am circuit. If I could find a handful to play with, I'd be cool.
The TDA1046 IC, identified on the website for the data sheet as "AM Empfängerschaltung mid Demodulator" also travels under the name of TDA4001, which is identified on its data sheet as "AM receiver IC with Demodulator." The chip is what it says it is, but looking at what information there is leads me to suspect that it wouldn't make a very good HF radio. The oscillator is only spec'd out for 1.5 MHz and the IF is shown only at 455 kHz. Still . . .
And there's the TBA651, which is shown as a tuner & IF amp for an AM radio. Like the TCA440, this chip is the basic IF section of a standard AM radio. There's an IF output to a transformer in the design notes, with the output of the IF transformer being a simple diode detector feeding an external AF amp. Replace the diode with a product detector and it might make a good CW/SSB radio . . . if you can do that at the spec'd 455 kHz IF.
The TAD100, an IC from the late 60s, is another of the "basic AM radio" chips. The datasheet suggests a circuit covering LW and MW bands. And a two transistor AF amp. Yeah, it's that old.
Out of the whole batch, the TDA1072 (and the TDA1572 version) is the most sensible of ICs to go with. First off the oscillator is spec'd to 50 MHz. And the IF has proven in experiments to work in the 4 to 9 MHz range. It has a detector bypass (which must be capacitor grounded to get any AF out of the detector) which in one online application provides for BFO injection. There are two AGC lines, one of which must be coupled to ground for the detector to work. And the chip has a mute line that must go to ground in receive.
The next possible winner is the TDA1083. With this one you get a nominal mute line (which actually shoots between an AGC function or an AFC function; the IC is touted as a AM and FM receiver) & AGC. You get the ability to use an external oscillator (with a weird looking coupling mechanism that others have used successfully). And there's a pick-up point at the second of two IF amp stages to use an detector outside the chip itself (or to inject a BFO signal). And there's the .25 W AF amp, which is one less thing to fight with if you're like me. The only drawback is the way the IF system works and what to me looks like a kind of haphazard IC pin layout. There are a couple designs on the InterWebs using this IC, including one for a 75m SSB transceiver.
Of course, if you don't want to play with one or two ICs to build a radio, then you've got the NE602/MC1350/NE602/LM386 circuit common to a whole list of tiny radio kits.
Now I started on this madness over ten years ago, at least to my reckoning. Over that time, other than amass a small fortune in ICs, some of which I parceled out to friends with greater levels of determination than I, I've done nothing with the idea.
Then I found a design on the web from one of the original unindicted co-conspirators. That design, using a 4.915 MHz IF, seemed reasonable and, with as few parts as the design had, possible for my shaking hands and short attention span.
Now, after months of burning things up and winding tiny toroids and all the other accumulated million aggravations that beset any project that I start, I've gotten to the point where I can say three things about the single-chip radio project:
That being said, here's a picture of what happened the last time I messed with this design. It isn't that bad of a radio, really. The only problems I have – and they're problems that I feel are more owing to my klugish way of putting things together before I get out the real metal working tools – are oscillation & instability in the input circuit. And there's a small problem with the BFO injection level and more importantly, a bit of trouble getting the BFO frequency set solid. Minor stuff, right?
After that, it's a good enough deal to listen to Radio Habana on, which was the original goal nearly a decade ago when I first got a bug up my kilt over this single-chip receiver madness.
I came across quite a few ICs, actually.
There's the TDA1072AT, which I will extrapolate on below.
The TDA1572 chip is the gussied up version of the '1076 with a separate IF output for whatever uses one might dream up.
There the TDA1083, which is everything you need for a receiver, including a small .25W audio amplifier. It's laid out a little weird but it looks like a promising trip. (I say looks like because I have ten of 'em and have yet to fiddle with a single one for any purpose at all. Limits.)
Then there are a handful of other ICs, most of 'em Sony chips, many of which are no longer available except in vast quantities from warehouses here and there in the Orient or wherever. Among these are the TCA440, which is a pretty neat little RF/OSC/MIX/IF chip for which the builder must provide a detector & AF am circuit. If I could find a handful to play with, I'd be cool.
The TDA1046 IC, identified on the website for the data sheet as "AM Empfängerschaltung mid Demodulator" also travels under the name of TDA4001, which is identified on its data sheet as "AM receiver IC with Demodulator." The chip is what it says it is, but looking at what information there is leads me to suspect that it wouldn't make a very good HF radio. The oscillator is only spec'd out for 1.5 MHz and the IF is shown only at 455 kHz. Still . . .
And there's the TBA651, which is shown as a tuner & IF amp for an AM radio. Like the TCA440, this chip is the basic IF section of a standard AM radio. There's an IF output to a transformer in the design notes, with the output of the IF transformer being a simple diode detector feeding an external AF amp. Replace the diode with a product detector and it might make a good CW/SSB radio . . . if you can do that at the spec'd 455 kHz IF.
The TAD100, an IC from the late 60s, is another of the "basic AM radio" chips. The datasheet suggests a circuit covering LW and MW bands. And a two transistor AF amp. Yeah, it's that old.
Out of the whole batch, the TDA1072 (and the TDA1572 version) is the most sensible of ICs to go with. First off the oscillator is spec'd to 50 MHz. And the IF has proven in experiments to work in the 4 to 9 MHz range. It has a detector bypass (which must be capacitor grounded to get any AF out of the detector) which in one online application provides for BFO injection. There are two AGC lines, one of which must be coupled to ground for the detector to work. And the chip has a mute line that must go to ground in receive.
The next possible winner is the TDA1083. With this one you get a nominal mute line (which actually shoots between an AGC function or an AFC function; the IC is touted as a AM and FM receiver) & AGC. You get the ability to use an external oscillator (with a weird looking coupling mechanism that others have used successfully). And there's a pick-up point at the second of two IF amp stages to use an detector outside the chip itself (or to inject a BFO signal). And there's the .25 W AF amp, which is one less thing to fight with if you're like me. The only drawback is the way the IF system works and what to me looks like a kind of haphazard IC pin layout. There are a couple designs on the InterWebs using this IC, including one for a 75m SSB transceiver.
Of course, if you don't want to play with one or two ICs to build a radio, then you've got the NE602/MC1350/NE602/LM386 circuit common to a whole list of tiny radio kits.
Now I started on this madness over ten years ago, at least to my reckoning. Over that time, other than amass a small fortune in ICs, some of which I parceled out to friends with greater levels of determination than I, I've done nothing with the idea.
Then I found a design on the web from one of the original unindicted co-conspirators. That design, using a 4.915 MHz IF, seemed reasonable and, with as few parts as the design had, possible for my shaking hands and short attention span.
Now, after months of burning things up and winding tiny toroids and all the other accumulated million aggravations that beset any project that I start, I've gotten to the point where I can say three things about the single-chip radio project:
- 1. It is possible to use the TDA1072AT chip to make a shortwave radio with nearly single-signal detection, even using 455 kHz ceramic filters. (I used a 455 kHz ceramic resonator for the BFO.)
- It is possible to get a reasonable CW/SSB system out of all this accumulated soldering, burning, cursing and quick turn down of the AF gain pot.
- If you want to build one of these, I'll be finished writing up what I've found – much of it with the help of my fellow unindicted co-conspirator – for eventual publication in some QRP ham radio magazine. And note that I said eventual publication. I don't do command performances any more.
- Oh, one more thing: I'm tired of working on this . . .
That being said, here's a picture of what happened the last time I messed with this design. It isn't that bad of a radio, really. The only problems I have – and they're problems that I feel are more owing to my klugish way of putting things together before I get out the real metal working tools – are oscillation & instability in the input circuit. And there's a small problem with the BFO injection level and more importantly, a bit of trouble getting the BFO frequency set solid. Minor stuff, right?After that, it's a good enough deal to listen to Radio Habana on, which was the original goal nearly a decade ago when I first got a bug up my kilt over this single-chip receiver madness.



After much fiddling & figuring, I ordered a
All this spending and discovery led to the present version of the Z-match shown here. It's a lot easier to use than the QPack and doesn't take up much more space, even if the box is higher. The knobs being on the front panel, I discovered, makes the tuner a little easier to use. (I'd discovered using the QPack that I needed an extra hand or some means of tying the QPack down while I twisted the knobs and fiddled the switches, a serious design criterion for QRP pack-and-go set-ups.)

$5k. Long way from that.
volume controls all the way up: on the computer and on the control panel on top of the desk. She was trying to play a video that had been recorded with almost no audio level.
couple hours here and there and be done with it. Sometimes I'd have a couple pages of the log book filled up and sometimes I'd have a page on a good day. Either way there were contacts in the log.
Now the art of a QSL is pretty precise. The most important part is the text block area where the contact with another ham via radio is verified with a strangely vague minutiæ for which hams are famous. It all comes down to time, date, frequency, signal report & who the hell was listening or talking. Five or six lines of ten point type on ten pica slug will do the job.
Little Printshop, another place that may no longer be in business. (There are two places listed on the web under Little Print Shop. Ain't sure if any of them's the one I'm remembering.)
A while back I came across a QSL card design that I really like. The QSL info is on the left side of the card, separated by a border design of some sort or the other. To the right of that is the call sign in another color and then the geographic & operator information goes above and below the callsign.
heavy metal printing, takes a lot of time and it's not exactly outside of the world of the physical.
