Category Archives: Amateur Radio

Arduino + MCP4725 Breakout Board

Well, the other I2C based breakout board I got from Sparkfun was for a Microchip MCP4725 DAC. It’s a 12 bit device, and will eventually do duty controlling the voltage controlled oscillator in my beacon transmitter. For tonight though, I just wanted to make sure I could program it, so I soldered on some header pins, plugged it into a breadboard, and coded up a small, simple program to simply send values from a table holding appropriately scaled sine values as quickly as possible. Here’s the code:

[sourcecode lang=”C”]

#include <Wire.h>

void
setup()
{
Wire.begin() ;
}

#define MCP4725_DEVICE 96

int sintab[64] = {2147, 2347, 2545, 2737, 2922, 3100, 3267, 3422, 3564, 3692, 3803,
3898, 3975, 4033, 4072, 4092, 4092, 4072, 4033, 3975, 3898, 3803,
3692, 3564, 3422, 3267, 3100, 2922, 2737, 2545, 2347, 2147, 1947,
1747, 1549, 1357, 1172, 994, 827, 672, 530, 402, 291, 196, 119, 61,
22, 2, 2, 22, 61, 119, 196, 291, 402, 530, 672, 827, 994, 1172,
1357, 1549, 1747, 1947} ;

int sp = 0 ;

void
loop()
{
Wire.beginTransmission(MCP4725_DEVICE);
Wire.send(64); // cmd to update the DAC
Wire.send(sintab[sp] >> 4); // the 8 most significant bits…
Wire.send((sintab[sp] & 15) << 4); // the 4 least significant bits…
Wire.endTransmission();
sp = (sp + 1) & 63 ;
}
[/sourcecode]

And here’s the brief YouTube video showing it in operation:



DS32kHz 32.768kHz Temperature-Compensated Crystal Oscillator

In considering the long term accuracy of the RTC chip that I was playing around with, I did some additional thinking and reading. My understanding is the error comes from the accuracy of the crystal oscillator: the 32.768Khz timing crystal probably has an accuracy of 20ppm or even larger. My guess is that this is expressed in two kinds of instability: a long term bias, which conceivably could be trimmed using a trimming capacitor, and a thermal component, which could be solved by temperature control. But in digging around, it appears that Maxim makes there own temperature controlled crystal oscillator, that has errors down in the 2ppm per year over a temperature range of 0 to 40 degrees Centigrade. Pretty nifty. They come in DIP (but non-stocked @ digikey) and various SOIC/BGA packages, with costs that might average around $10, which seems a bit spendy, but worth considering.

DS32kHz 32.768kHz Temperature-Compensated Crystal Oscillator – Overview

Kenneth mentioned the DS3232 as a more accurate version of the DS1307: it appears to me that the specifications for it are identical to the specification for the DS32kHz TXCO. My guess is that it’s simply an integrated package, but I haven’t had the chance to look at the datasheet yet. It does appear to be cost effective: you can get them from digikey in quantity one for less than five dollars. Worth looking into.

Addendum: Kenneth could have plugged his own excellent page on his build of a DS3232 based clock. Very nice, and includes a supercapacitor backup circuit for the DS3232. As it happens, I picked up a couple of supercaps from sparkfun with this order: I might have to give this a try.

Arduino + DS1307 Real Time Clock

Okay, this is no big deal: lots of people have done it before. But while I was watching TV, I soldered some header pins to the DS1307 based real time clock board I got from sparkfun.com , and coded up this simple program to read the time from it. I’d never really used the Wire library, but it’s pretty straightforward. I plugged the board into a breadboard, jumpered it into the Arduino, and with a bit of tweaking, it works.

[sourcecode lang=”C”]

#include <Wire.h>
#define DS1307_I2C_ADDRESS (0x68)

byte h, htmp, m, s ;
byte dow, dom ;
byte mn, yr ;

byte
BCDToDEC(byte val)
{
return (val >> 4) * 10 + (val & 0xf) ;
}

void
doDate()
{
Wire.beginTransmission(DS1307_I2C_ADDRESS) ;
Wire.send(0x0) ;
Wire.endTransmission() ;

Wire.requestFrom(DS1307_I2C_ADDRESS, 7) ;

s = BCDToDEC(Wire.receive() & 0x7f) ;
m = BCDToDEC(Wire.receive()) ;
htmp = Wire.receive() ;
dow = BCDToDEC(Wire.receive()) ;
dom = BCDToDEC(Wire.receive()) ;
mn = BCDToDEC(Wire.receive()) ;
yr = BCDToDEC(Wire.receive()) ;

if (htmp & (1<<6)) {
/* 12 hour mode… */
h = BCDToDEC(htmp&0x1F) ;
} else {
/* 24 hour mode… */
h = BCDToDEC(htmp&0x3F) ;
}

if (h < 10) Serial.print("0") ;
Serial.print(h, DEC) ;

Serial.print(":") ;
if (m < 10)
Serial.print("0") ;
Serial.print(m, DEC) ;
Serial.print(":") ;
if (s < 10)
Serial.print("0") ;
Serial.print(s, DEC) ;

if (htmp & (1<<6)) {
if (htmp & (1<<5))
Serial.print("PM") ;
else
Serial.print("AM") ;
}
Serial.print(" ") ;

Serial.print(mn, DEC) ;
Serial.print("/") ;
Serial.print(dom, DEC) ;
Serial.print("/") ;
Serial.print(yr, DEC) ;
Serial.print("\n") ;
}

void
setup()
{
Wire.begin() ;
Serial.begin(9600) ;
}

void
loop()
{
doDate() ;
delay(1000) ;
}
[/sourcecode]

Nothing earth shattering here. Eventually, I want my beacon controller to have a real time clock, and this seemed like a good way to go. Having a reasonably accurate real time clock means that I can make my beacon send WSPR messages, which start at the beginning of even numbered minutes on the hour. Baby steps.

The Ham’s Inconsistent Love/Hate relationship with Progress and Technology

WARNING: pontificating and ranting ahead. You’ve been warned.

Tom pointed out that I had an inadvertent markup error which ended up dropping several paragraphs of this post. It is now corrected.

Julian, G4ILO followed up yesterday’s post about technology not being good for ham radio with a nearly equally confusing one today entitled Platform for progress. I find it confusing because the over the bulk of it, I’m entirely in agreement. He says that there are a (presumably significant) number of technophiles who get involved in amateur radio, only to drop out immediately when they realize that it isn’t a replacement for the cell phone or Internet because the infrastructure isn’t as extenstive or reliable as they expect. I’d agree that is probably true, although it’s hard to say that hams who never really become active have any actual negative effect on the hobby.

He then goes on to criticize the existing top end of HT radios, and in most respects I agree with him. When I compare the level of technology that’s inside my VX-8GR to the level of technology inside my two year old iPhone 3GS, the difference is palpable. But I think that’s mostly unfair: after all, the iPhone is cutting edge mass market product, with sales in the millions, and the VX-8GR will probably sell a few tens of thousands of units. And, of course, the IPhone’s purchase price is in most cases heavily subsidized by high fees from the cell phone companies which are simply not available to ham radio manufacturers.

But even taking those things into account, the state of the art in ham radio HTs is maddeningly primitive, and in ways that make operating your radio more difficult and more confusing. My VX-8GR has impossibly small buttons in an undistiguishable array on the front. Many important functions require pushing both a function key on the side and then a button on the front, a maneuver which cannot be done with one hand, and if you were left handed, require a very odd grip. The display is small and often fails to contain useful information, while commonly cluttered with information you don’t need. All the APRS functions are hidden behind the need to hit the MODE button, which puts you in a different mode, with different setup options, and a similarly bewildering method for navigating among APRS messages. Programming memories is (as it is on virtually all radios) a similarly mystifing barrage of error prone button clicks. It’s simply horrible.

And yet, it’s probably one of the better and more capable radios out there. Go figure.

Julian’s vision of how HTs could be transformed is remarkable, and I wish that ham radio manfuacturers would listen to him. While some people criticize attempts to make things easier to use as “dumbing down”, I completely disagree. No good purpose is served by poor interfaces, even for experts. It’s ridiculous how much effort it takes to get a radio programmed with local repeaters. I recently did this for the VX-8GR, and it involved:

  • Buying a custom cable and software, because even if you had the cable (which is of course not a standard type), you still can’t find software to program the radio for free, despite having spent $350 on the radio.
  • Surfing over to K5EHX’s awesome repeater site and downloading an export of all the local repeaters.
  • Loading them into the software, and then deleting obvious duplicates and bad data.
  • Organizing them into banks.
  • Adding a bunch of FM satellite frequencies, along with Doppler shifts for satellite operation.
  • Adding in APRS setups for both terrestrial (144.390) and satellite (145.800) frequencies.

I can imagine a world where I plug the radio in, visit a website, and all this happens automatically. Would this be dumbing down amateur radio? Of course not. It doesn’t take any particular intelligence to program a radio: it’s just a bit of tedium that could reasonably be automated. But the state of the radio art is a long way from making this happen. What’s more, because most radios hide behind undocumented protocols and stupid non-standard cables, it isn’t even possible for guys as clever as K5EHX (who programmed and maintains the repeater maps himself) to step up and make life easier for everyone.

So, Julian and I are in violent agreement, right up until the end of today’s post, where he says:

So why won’t this happen? I guess the reason for that is that Yaesu, Icom, Kenwood and the rest don’t make cellphones. Their business is making radios that are intended to be as dumb as most of their users. Ham radio is just an offshoot. The market just isn’t big enough to justify developing what for them would be a completely different and unique hardware platform. So I guess for the foreseeable future we’ll be stuck with our geeky walkie talkies and the cool stuff will all be on cellphones.

Argh. First of all, I don’t see how anything good comes out of insulting a bunch of your fellow hams. Our own intelligence lies along a continuum, and while I admit that there are a lot of people considerably stupider or less experienced than I, there are also a whole bunch of people on the other side who are considerably smarter and more experienced. It’s hard to understand how calling other people stupid actually enhances ham radio. James has pointed out that Julian was likely referring to business and public radio users as being “dumb”. I’ll strike the previous paragraph as a misunderstanding of his point. I do think that Kenwood, Yaesu and Icom don’t design ham radios the way they are because of any conviction that their radios need to be simple (in fact, I’d say that they are needlessly complicated to use, as my examples above were meant to indicate) but that simply they have successfully sold radios of similar design, and their isn’t enough competition for them to invest in improving them in significant ways. I also think it is possible (but I have no evidence to support it) that there might be some fear that a significantly new and radical architecture for radios might be met with some trepidation by hams, who have a reputation of not being the most progressive and quick to adopt new things.

Secondly, it presumes that technological advances in ham radio must come from manufacturers. Even today, that simply isn’t true: modes like APRS and PSK31 were originally designed by amateurs, and have been copied and extended by amateurs until the manufacturers took notice, and are just now being adopted as features in products. We also see software defined radio in inexpensive amateur kits like the Softrock, and now adopted into semi-commercial products like The SDR Cube. My guess is that you’ll see a commercial offering of similar capability reasonably soon. My point: we can serve to lead and inform manufacturers what technology we find interesting by developing it ourselves, and creating a market for it..

Lastly, I’m exasperated by the fatalism that is expressed by these kind of statements. Here and in the responses to yesterday’s article, Julian expressed doubts that “ordinary hams” could learn enough about SDR or acquire the ability to work with surface mount parts. I’m baffled by this kind of negativity. Here in the U.S. we are regulated under Part 97, which says that the amateur radio service was created to allow for self training, experimentation and advancement of the radio arts. It doesn’t say anything about mastering “just the easy bits” or “just the non-software bits”. Julian also made the claim:

Those that have the expertise to experiment with new technologies in ham radio probably learnt those skills professionally. The reason why I am against the incursion of advanced technologies into this amateur hobby is that it forces more and more of us true amateurs into being mere appliance users.

I don’t really mean to pick on Julian, but I find this to be almost entirely wrong. First of all, everything I know about amateur radio, electronics, digital signal processing and microcontrollers I learned because of personal interest, and I know literally dozens of people of similar stories. And of course, there have always been skilled amateurs in our ranks who learned their material as professionals, and brought their skills to amateur radio. Julian appears to be saying that the participation of skilled, professionally trained people in amateur radio is undesirable. I find that baffling.

I also think his conclusion is odd. To me, the inclusion of software technology into amateur radio serves as an incentive to bring large numbers of skilled software engineers into the ranks of amateurs, enabling new applications and new techniques. The vision I have for the future of amateur radio is one where we are more more engaged, not less. Furthermore, if we drag our feet in adoption of technology, amateur radio as a whole becomes increasingly irrelevant as the rest of the world advances in technology. We simply become a kind of technological re-enactment society, like a kind of radio Rennaissance faire. (Apologies to those who like Renaissance faires…)

Ham radio is a very odd endeavor: for an activity which is centered around one of the greatest advances in technology in human history, we have a surprisingly large number of people who treat it with mysticism, who want to hold it just at the level that they themselves feel comfortable, and who resist efforts to change or advance it. There are radio amateurs who are obsessed with tube rigs, and refuse to consider modern solid state design. They’ll tell you there is something just inscrutable about transistors, but the truth is, they’ve never manufactured a tube, and for the most part, tubes are just as inscrutable as transistors. SImilarly, there are people who refuse to use ICs in their rigs, because somehow it just seems to be “cheating” to use a device that integrates more than one gate in a package, even though making transistors is just as inscrutable as making ICs. You’ll find people who don’t want microprocessors, so they do crazy things like using 555 timers in reckless abandon, with all sorts of diode based switching, when a $2 Atmel chip will do the same and more for less money and actually with less circuitry.

Julian’s blog has lots of really cool stuff, stuff that has inspired and challenged me to learn and do more. I hope he continues with it. Like him, I’m eagerly awaiting G3XBM’s DSB 10m rig design, and hope to be constructing one. I’m still playing with beacons, and APRS and other things that he’s interested in. I just wish we could send out a consistent, careful message to our fellow hams and potential hams to be that technology and amateur radio aren’t strange bedfellows. We are the Amateur Radio Service, not the Antique Radio Society.

Is technology good for ham radio?

Over at G4ILO’s blog, he responded to the recent Wired article about ham radio by asking “Is technology good for ham radio?” with his answer being “no”.

G4ILO’s Blog: Is technology good for ham radio?

The statement which caused me to blow milk out my nose was this one:

The more high-tech ham radio becomes, the less magic there is.

I must admit that such statements cause me to roll my eyes. Ham radio wasn’t ever magic. It seemed like magic, because it allowed you to do something which you couldn’t imagine doing without it: communicate with others over hundreds or thousands of miles. It’s hard not to think of this as magic, a quote attributed to Einstein (but as far as I know unverified) goes:

“The wireless telegraph is not difficult to understand. The ordinary telegraph is like a very long cat. You pull the tail in New York, and it meows in Los Angeles. The wireless is exactly the same, only without the cat.”

That makes it sound very much like magic, but it’s really not, and moreover, it never has been. On my desk I have a copy of The Principles Underlying Radio Communication, a really nifty little book put out by the U.S. Army Signal Corp. The first edition was published in 1918, and you can read it online via Google Books (my own copy is dated 1921).

If you bother to read this book, it isn’t magic or alchemy: it’s engineering and science, harnessed in the service of human communication. You’ll learn about currents and resistance, about Ohm’s law and batteries, about capacitance, magnetism and inductance. And because this was in the days just after WWI, you’ll see the use of alternators to generate radio waves, and the first hints of the use of vacuum tubes (the most cutting edge of technologies for its time). Amateurs were following right along through all this. If you surf the QST archive available from the ARRL, you can see that dedicated amateurs were tracking these amazing developments with incredible rapidity and skill. The history of amateur radio is one of technological adoption, not historical preservation. It was about challenging one’s self to do something that seemed like it would be beyond the realm of what could be done by individuals, working on their own with resources limited by what they could afford.

To me, amateur radio is about setting personal challenges, and then working to achieve them. I’ve called it “going boldly where others have gone before”, and if that seems odd to you, consider that you might want to see the Louvre, or Westminster Abbey, or Chitzen Itza with your own eyes even though you could just buy books and read about them. It’s about learning and growing and sharing with people of similar interests, and I see technology as only enabling more of that.

G4ILO maintains a webpage and a blog. If you surf over to his page, you can see a picture of his shack, which has at least nine radios which contain microprocessors. (In fact, I don’t see a single one which doesn’t.) I suspect you’ll find a couple more microprocessors in the visible power supplies and tuners. If technology is bad for amateur radio, I wonder why Julian seems to possess so much of it? If technology is such an anathema, a threat to the magic of amateur radio, then shouldn’t we all just go back to alternators, audions and spark gaps?

Technologies like cell phones and the Internet are incredible tools to bring the world closer together, and to allow us to communicate and share our part of the human experience. When we talk in hushed tones about the good old days when amateur radio was king, we just look foolish.

I do agree with Julian about a few things: I’m not a fan of D-Star, not because it uses the Internet (the Internet significantly extends its utility for hams) but because it relies on a patented technology which must remain forever (well, until the patent runs out) beyond the realm of experimentation and deployment. But the problem isn’t one of technology: it’s one of ownership. I also think that the ARRL (which does do a great many good things) doesn’t serve amateur radios best interest by promoting it mostly as an emergency radio service. As other communication technologies become more pervasive, it seems clear that amateur radio’s role is shrinking over time, and even if we were to reverse that trend, we’d basically be simply duplicated a radio network that could be provided by the government or by private industry.

Technology can be scary, but it also can be exciting and empowering. Let’s embrace technology, rather than drag our heels and complain that we can’t understand it. Let’s rise to the challenges that we have inside us to learn, to experiment and to embrace.

G3XBM: A Simple Sideband 10m Transceiver

I always like reading G3XBM’s blog: he’s been interested in all kinds of cool QRP and LF stuff that I find really intriguing. What makes it even more great is that he’s decided to apply his significant talents toward designing a very simple sideband rig for 10m. It looks like he’s aiming toward a dual sideband rig with a simple direct conversion receiver, with a target price of around $32 US. Very intriguing! I’ll be monitoring this closely. As the sunspots heat up, a little rig like this could be an awesome amount of fun.

A Simple Sideband 10m Transceiver – G3XBM.

Ideas for expansion of the QRSS beacon…

I haven’t even got this on the air yet, and I’m already imagining all sorts of interesting possibilities to improve and change the basic beacon design. (This is a credit to Hans for creating something simple enough to build, and yet interesting enough to inspire.) I’ve been brainstorming a bit this morning, and thought that I’d just write down some of the ideas I’ve had.

  • First, there is the question of output power. I think that with the 3v supply (probably more like 2.8v) the maximum output power is somewhere around 14mw. This might suffice for reports for other DX entities in Europe, but to reach other countries from the U.S., a few additional milliwatts (say between 100 and 250mw) would be better. I suspect that I’ll have to go to a 6v supply to make that happen, but in any case, it’ll be an interesting thing to work out.
  • Even without additional power, the addition of an output buffer amp is probably good. I noticed that even changing the configuration of the short wire that i was using as an antenna changed the loading of the oscillator to shift the output frequency a few hertz.
  • Temperature control would probably be a good thing. Stu Phillips had some nice ideas in his own QRPp transmitter, which is probably worth emulating.
  • It seems silly not to make more use of the Arduino. If I had a thermister or some other temperature sensor, I could log temperature. I could also use it to monitor battery voltage. I am also pondering using one of the cheaper processor boards: perhaps a LaunchPad ($6 is a lot cheaper than $30 or so for an Arduino).
  • Using the PWM outputs of the Arduino as analog control voltages means constructing a discrete a low pass filter, or a resistor ladder. This is fine for mucking around, but using a proper DAC might also be good. Microchips makes a nice little I2C 14-bit DAC that you can get from Sparkfun on a little breakout board for $5. I suspect that if you monitored the temperature using the processor, you could calibrate the output frequency to stabilize the output with respect to temperature digitally.
    Breakout Board for MCP4725 I2C DAC – SparkFun Electronics.
  • Oh, and put it in a proper metal box. With perhaps a variety of inputs and outputs. Including maybe a tap that I could use with my Norcal frequency counter.

Okay, that’s a pretty good list. Should keep me busy for quite some time.

Bummer! No Wednesday deployment of ARISSat-1

The Southgate Amateur Radio News is reporting that ARRISSAT-1 will not be deployed during an EVA from the ISS this week as previously planned. It now appears that it will remain on board until July.

No Wednesday deployment of ARISSat-1 | Southgate Amateur Radio News.

3. AMSAT learned on Friday morning, 11 FEB 11 that the deployment of the ARISSat-1 satellite had been removed from the RSA EVA 28 timeline by RSC-Energia management. NASA was informed that the ARISSat-1 deployment would be deferred to a later RS EVA, due to changes in the tasks associated with the configuration of RS payloads to be performed during RS EVA 28.

Subsequently, RSC-Energia informed NASA that deployment of ARISSat-1 will be added to RSC EVA 29 currently scheduled for July 2011.

The K6HX Arduino QRSS Beacon (ala Hans Summers, G0UPL)

So, today I drove down to HSC in Sunnyvale and got (among other things) some trimmer capacitors so I could tune my beacon, and when I got back, I set to work. I pulled the 22pF capacitor and put in my trimmer, and then hooked up my SDR-IQ receiver to the laptop so I could see where the radio was tuning. A few tweaks with a screwdriver (wish I had a non-metallic one for this) and I got it centered in the band between 10.140Mhz and 10.140100Mhz. It seemed to stay there pretty well. I had previously made a simple input filter on the board (consisting of a 10K resistor, and a 22uF capacitor (too high, but it was what I had on hand). I wired it up through a 1M ohm resistor (as per Hans’ schematic) and then took the voltage from the two AA supply (let’s call it 3v, even if it is really somewhat less) and tapped it into the input. Sure enough, the radio tuned up about 40Hz. When I removed it though, the filter drained really slowly, returning to its original value only after twenty seconds or so. I thought this was going to be a problem, but then I realized that the filter capacitor had to discharge through the 1M ohm resistor, because the input was floating, but when hooked to my Arduino, it would would discharge back to the ground inside the Arduino through the 10K resistor, which would mean that it would discharge 100x faster. That seemed to work out in practice as well.

But my first test was simply an unfiltered test: sending either the high or low value to an output pin, and sending it into the modulation input of the beacon. To generate the keying waveform, I just modified my earlier Arduino Morse Beacon to send at 1 second dits, and then used Spectravue on my SDR-IQ to scan a relatively small (500hz) bandwidth. A few seconds later:

I then tried sending the input through the smoothing filter. As you can see, the waveforms now look fairly rounded:

But the Morse is still clearly legible. I decided to leave the input filter as it was, since in QRSS3 mode, the dits would be 3x longer. Measuring the overall frequency deviation, it seemed like it was about 50 or 60 hertz. Rather than setting up a pot as a voltage divider, I instead programmed the Arduino to vary its voltage between 4 and 5 volts, which I figured would give me 1/5th the total deviation, or about 10 hertz. And… it works! Witness the absurd and poorly lit video, demonstrating reception via my FT-817 and Spectran, but still transmitting into the same 50 ohm resistor at the lowest power setting (I suspect right around 2 or 3 mw).

Bill, N2CQR will probably appreciate that initially, I seemed to be generating upside down Morse as well. I modified the program to flip the Morse around, and all was well. But then I moved this radio to hook it up again, and the Morse code seemed upside down again. So, I flipped it back. All is well. For now.

I was concerned about the stability, but it seems pretty good, considering that I just used the crappy stuff from my junkbox. Eventually, I’ll get it in a box to keep the temperature more stable, I’ll make some software improvements (perhaps sending Hellschreiber) and then get it on the air.

73 de K6HX

Addendum: Here’s the link to Hans’ design. Thanks Kenneth, for reminding me that I had forgot to link to the schematic. Click on “Construction”.

QRSS beacon, ala Hans Summers, G0UPL

My regenerative receiver was annoying me, and I wanted to do some soldering tonight anyway, so I thought I’d tack together a really simple transmitter project. I wound a coil, and spent about 45 minutes tacking a simple QRSS transmitter (really just a Colpitts oscillator) which should dump about 14mw of power into a 50 ohm load. I also created an LTSpice model for it, which I should put up in the next few days.

YouTube – QRSS beacon, ala Hans Summers, G0UPL.

More writeup later.

Addendum: Before crashing last night, I moved it out to my dining room table where my FT-817 was sitting, and verified that it does indeed seem to emit radio waves.

I’m trapped in the Regenerative Receiver Circle of Hell…

I’ve listened to the SolderSmoke podcast for quite a while, and you’d think I would have availed myself of Bill’s sage wisdom. He’s previously made mention of the endless fun and rapture he’s had tinkering with crystal radios, carried away to the sounds of heavenly lutes (okay, I’m extrapolating here). But he’s also mentioned that he’s had considerably less fun with regeneratives: indeed, proclaiming that they must come from the place where all the solder smells like brimstone.

SolderSmoke Daily News: Crystal Radios from Heaven, Regens from ?

You think I would have listened. But no: I had to try to tinker together N1TEV’s Ultra Simple W1AW Receiver. I’ve now got the all the worst features of regeneratives:

  • Hand capacitance: the oscillator wavers and even halts when I touch the regenerative control.
  • The oscillator starts and stops unpredictably. If you adjust the regeneration control until the oscillator starts, you can back up and it will stay running until it suddenly clicks off.
  • Gain is pretty low. I can just barely hear W1AW, along with some of the digital signals within the band. I installed the optional volume control to boost the level, which helps some, but it’s not brilliant.
  • Antenna loading seems to do odd things to the antenna too.
  • Touching anything in the circuit seems to quench oscillation.

I did gain a few bits of knowledge in doing this project, but frankly, it’s annoying. Perhaps in the light of day, when the clerics of electronics have said their prayers for my salvation, this thing will seem worth investing time in debugging. I have no doubt that if I lived only a hundred miles from W1AW, this would work, but it’s not inspiring me to greater investment of time.

I think I’ll convert to the Direct Conversion faith for my next project.

USB: technology du jour, or evolutionary leap?

G4ILO has a post on his blog grumbling about the increasing use of USB technology in amateur radio:

G4ILO’s Blog: USB technology du jour.

As seems typical with many things he talks about, I disagree with virtually all of his points.

My position: I absolutely hate special purpose cables. My FT-817 has some wacky DIN-6 or something on the back. My TH-D7A (and I think the VX-8GR) use a 2.5mm plug to carry data. Every time I have to buy a special purpose cable, I grimace, mostly because I know that they are shafting me out of $30 or whatever for a cable that provides about $2 worth of manufactured value. USB has three (or is it four) plug types, but at least they are commodity items: you can get them inexpensively if you hunt around, and chances are you probably have a couple of the right type from a phone, or a disk drive, or whatever.

It’s nice that G4ILO’s shack has four different serial ports. I have one machine in my office that has a DB-9 in it, but I have six other machines which combine to provide probably two dozen USB ports. If I want to add a couple of ports to something, I have a $7 powered hub that I keep around (it was useful a couple of times with a laptop that provided only one USB port). G4ILO tries to portray USB as being the side with limited expandability, when precisely the reverse is true: USB has much greater expandability.

There is one criticism which I think is valid: I despise manufacturers who require the use of proprietary drivers to access functionality. Luckily, the USB standards folks have figured this out: USB defines class codes. This means that you can create devices which comply with certain USB specifications, and the USB devices simply work. You plug in a device, and it is recognized as a serial port, or an audio card, or a modem, or an ethernet controller. I love the idea of the TH-D72a: you simply plug in a USB cable and plug it into your computer, it recognizes it as a serial device and creates the necessary device entries. Windows/Mac/Linux, it all just works.

Yes, if you wanted to hook it to a microcontroller, it isn’t that helpful. So in exchange for making it work better for 99.9% of the people, it doesn’t automatically fufill the needs of of the .1%. I’ll take that tradeoff any day.

Sending analog audio down cables sounds great, and of course we find that radios like the TH-D72a of course still have audio inputs and outputs. But having digital ones via USB opens up lots of possibilities: like sending data noiselessly, and being able to control levels with actual program controls.

Do we need plug and play controls on our radios? ABSOLUTELY. There is nothing about ham radio that implies that we have to be masochists and invent the kludgy solutions that everyone else in the universe is well beyond.

USB is hardly a technology du jour. It’s perhaps the single most widely supported standard in computing, is supported on every major operating system, and has created a huge industry of peripherals that are simply expected to work.

As for longevity: who can tell, but I’ll simply say that I’ve had USB peripherals since the Windows 95 days. It was rocky back then, but fifteen years later, they are still going strong.

As consumers (and most of us are consumers of ham radio stuff) we should expect better from the manufacturers. Radios should use well-developed USB technology.

My weekend project: Ultra-simple W1AW Receiver

Okay, I’ve been wanting to actually do a little radio project for a while. So, instead of cleaning and organizing my home office some more, I decided to go ahead and tack something together. So, the project I settled on was N1TEV’s “Ultra Simple W1AW Reciever” from the May 1997 QST. I had most of the parts lying around, so I got a piece of copper clad and went to work.

Along the way I learned a few lessons:

  • When I first assembled it, the LM386 did what comes naturally: sounded like a motorboat. In discussing it with the the people on the freenode #hamradio channel (thanks especially to Aegis) I moved the power supply cap directly to pin six on the LM386 and the motorboating ceased.
  • I then hooked it an antenna, and was treated to a local FM broadcast station (106.7 FM). More discussions suggested that I could add a lowpass filter, but then I realized that I had forgotten to install the 1K emitter resistor for Q1. When I installed that, I stopped hearing the FM station.
  • I can hear the oscillator running. As I adjust the regeneration, the background noise starts low, and gets louder like I’d expect. I can also hear the signal from my FT-817 with just a short antenna hooked up.
  • As yet, I haven’t heard any live signals. Then again, I haven’t heard much on my FT-817 either, so maybe it’s just because there has been nothing to hear. W1AW broadcasts on 3.5815 Mhz, so I’ll hopefully get a chance to check it out tomorrow.

Using my RFSpace SDR-IQ receiver also shows the oscillator working:

This shows the oscillator at 3.5795, and as I adjusted the regeneration, it the frequency of the oscillator does shift. Interesting.

I’ll be testing it and playing with it some more over the next few days.

Is this really why ham radio endures?

David Rowan of Wired.co.uk has an article over on their website:

Why ham radio endures in a world of tweets (Wired UK)

He waxes philosophically about the thrill of establishing long distance radio communication, about receiving QSL cards, and gives mention to the role that ham radio plays in time of emergency.

I hear these things repeated a lot. They aren’t false, but neither are they entirely enough of the real picture to paint a realistic view of amateur radio.

It’s wrong to think of amateur radio as a single hobby: it’s a bunch of different hobbies all united by the need for a radio license. There are radio contests. There are people who chase awards. There are people who just want QSL cards to decorate their shack. There are people who setup FM repeaters to serve their communities. There are people who operate only low power transmitters (“QRPers”) often that they construct themselves. There are people interested in space communications such as satellite or EME operation (moonbounce).

Amateur radio continues to exist because radio amateurs continue to find their own areas of interest, do the necessary work to become licensed, and then pursue those interests. Whether it is contesting, construction, serving your community in times of emergency, or just plain old talking to your neighbors, people are still finding reasons to get licensed and get on the air.

I pursue amateur radio because I’m interested in the complexity of physics that allows radio to propagate. I’m interested in construction, and experimentation. And I’m interested in finding other people with similar interests. No advances in cell phone or computer technology will really blunt that. I suspect that each ham finds his own reason to pursue it, often beyond the point where any practical economic argument.

It’s what we do for fun.