For the first time in a couple of years, I got all my equipment back online in the WSPR mode. I used to run WSPR primarilly with my little Yaesu FT-817, but this time, I chose to go ahead and use my ICOM IC-735, which isn’t a really all that great at WSPR-ing: it is, after all a rig capable of a full 100W output, and even on its lowest power setting should beam out 10W of power. I’ve also suspected that in comparison to the receiver in the FT-817, it’s a bit deaf: it simply can’t hear weak signals.

Last night I left it simply listening on the 30m band. In previous attempts at WSPR, I could expect to hear signals from a couple of dozen different stations. In the last four hours, I’ve gotten two: NM7J in New Mexico and JQ2WDO in Japan. I think it’s a receiver/antenna issue, since I’m not seeing signals in the waterfall which aren’t being decoded: I’m simply not hearing them.

I’m going to move my monitor up to 20m for the day, and see how that works. But I think some antenna testing and maybe trying my trust FT-817 in its place would be a good way to proceed.

Lots of people have said that RTL-SDR dongles that they have been receiving don’t have ESD protection diodes on the antenna inputs, which makes them susceptible to damage, particularly when you hook larger, gain antennas to them. I had read many notes about the EZTV645 that I bought which indicated didn’t have the BAV99 diodes. I took it for granted that mine wouldn’t. But today, I decided to lever it open (it’s really easy, just stick a thumbnail underneath and pop it open). Here’s what mine looked like inside:

The little protection diode is there, right below the antenna connector. Cool.

I did some other testing with the standard antenna, since I didn’t have the appropriate adapter to really try it with anything else. It picks up fairly strong signals, like this recording I made of the nearby NOAA weather radio station on 162.425Mhz:

NOAA Weather on 162.425

I did a few tests. I unscrewed the tiny antenna from its base, and.. the signal was about the same. That suggests to me that the feedline is probably just about as good an antenna as the “antenna” proper. I pondered for a moment, and then attached an 18″ piece of wire to the base of the antenna mount. This should be about 1/4 wave at 162Mhz. The signal was about six db stronger, with fewer drop outs. Next project: to build some real antennas. High on my list are antennas for the 2M hand band, the 1090Mhz ADS-B aircraft telemetry band, and the 137MHz satellite transmissions. Stay tuned.

Just a brief note: this website has some pretty extensive pictures of the inside and outside of the same model of RTLSDR dongle I bought. It also shows that it does not have the ESD protection diodes in place, so it’s possible you could fry the tuner input by having a static discharge directly hit the input on the tuner chip. I’m pondering trying to get some BAV99s and install one anyway, but I also noted that many others are instead recommending getting this model from NooElec instead. They advertise that they use the R820T tuner, and have the ESD antenna protection in place. I do wish they used SMA connectors instead of MCX, but adapters are fairly cheap. I ordered one just to do some comparison testing.

I’ll let you know when it arrives.

I’ve already got a couple of software defined radios: a nice SDR-IQ from RFSpace which covers up to 30Mhz, and an original Funcube Dongle Pro which covers from 64Mhz to 1700Mhz. I like both, but I must admit: they were fairly expensive. Still, in some ways they have spoiled me for conventional receivers in at least one way: they allow easy exploration of the RF spectrum. Just tune through the bands, looking for signals, clicking to tune. Awesome.

But I’m always on the lookout for cheap gadgets, and there is a recent crop of USB gadgets which (while not specifically designed for radio experimenters) have been recently adopted to put a software defined radio within the reach of many more experimenters. These come in the form of “DVB/FM receiver dongles”. Originally designed to allow you to tune in FM radio and DVB-T (the European standard for terrestrial digital TV), but with the right software can be hijacked and use as a more general radio exploration gadget.

I’m just at the beginning of my exploration of this stuff, but here’s what I’ve done so far.

First of all, I ordered one of the dongles. You should be able to get one for about $20 or so. I chose to get one from Deal Extreme, an interesting Chinese exporter. Based on some misinformation, I chose this EZCAP EZTV645, which was $19.20 shipped. Note: I do not recommend this particular radio. You can probably find a better one. I was misinformed into believing that this radio contained the “Elonics E4000 tuner”, which is generally the preferred tuner to use. Other good tuners are apparently the R820T. This one contains an FC00013, which certainly works, but is generally considered the least desirable and has the smallest tuning range. It would also be good to get one which has a standard MCX antenna connector, to make it easier to replace the absurdly comical antenna that it ships with.

The easiest way for many people to get started on Windows is likely to download SDR#, an open-source C# software defined radio program. On Windows, I recommend downloading the sdr-install.zip file, and using it to fetch all the goodies you need. You’ll then need to run “Zadig” (also downloaded) to install the right drivers, but I followed the instructions, and it worked fine, with one minor caveat: I have a Windows 8 laptop, and the drivers that you need to install are unsigned, so they can’t be installed unless you boot the Windows 8 machine in the special mode that will allow you to install unsigned drivers. Annoying. If you’ve never had to do it before, you can just google for the instructions, I fused this page as a guide, and it worked fine.

I haven’t had much time to play with this yet, but SDR# seems very nice (it also supports my SDR-IQ and Funcube Dongle, so I could in theory use it for all my SDR needs). Here’s a quick screenshot of it tuning an FM station:

You can clearly see the FM signal as well as the Radio Broadcast Data System (RBDS) which the receiver can also use to decode sogn titles and the like. Pretty neat.

One thing that sets these cheap dongles apart from the Funcube Dongle and the SDR-IQ is bandwidth: you can actually set this dongle to receive up to 3.2M samples per second, which means you can decode signals which are too wide to decode on the other radios (like DVB-T) or can search huge sections of spectrum at a time.

I haven’t had much of a chance to do more with this radio yet, in particular, I’ve only used it with its pathetic antenna inside my stucco-house and at work inside a metal framed building, where none of my HTs work very well either, so I don’t know of its sensitivity. But I’ll try to keep you all posted.

The other day I was in Ham Radio Outlet, and while strolling around I noticed a new VHF book published by the RGSB. And for some resaon, it made me think: I’ve got three different dual HTs, and an FT-817 which can work on 2m/70cm, why aren’t I doing more on VHF/UHF? I had a lot of fun operating via AO-51, AO-27 and SO-50, as well as the various APRS satellites, but except for SO-50, those have all gone black, and Fox isn’t due for a few months yet. I haven’t found repeaters to be very interesting overall: the sort of abstract social nature doesn’t seem all that exciting, and they represent little in the way of technical challenge. I like the idea of meteor scatter: I’d need to upgrade some equipment and build some antennas, but that seems reasonable. 2M weak signal SSB is probably something that would only pay off mobile (my home location is in a bit of a valley) but has some construction opportunities in it (antennas and the like). I’ve recently heard of coming Digital TV downlinks from the ISS, but haven’t got a clear idea of what hardware will be needed for reception.

I thought I’d toss is out to my readers: are there any VHF/UHF activities that you are participating in or would like to? I suspect that there are people who would like to have some new ideas, either because of limitations of their license class or their home situation, which may not favor large antennas. I’m also interested in hearing about any Bay Area groups who may do unusual activities on VHF+ frequencies.

This weekend was kind of a loss for computer/geek/rc airplane/ham radio, but it was off the charts fun for me and the missus. We did an unplanned day trip up to the Napa valley on Saturday, and then when I realized that I had left my lucky hat at restaurant, returned on Sunday to retrieve it, and ended up having a great brunch at Brix (yum) and then took a tour of the Bale Grist Mill.

The Bale Grist Mill is a fully restored, water-powered grist mill that grinds grain. We saw the sign on Saturday, and googled it that night, and decided to return on Sunday and see what the tour was all about. It was great: the miller was there leading tours, and spent about an hour talking about the history of the mill, and then allowing us to view all the intricate mechanisms inside that serve to grind grist (the seeds of either wheat or corn) into flour or meal. For a small donation, you can even cart away some of the resulting flour for yourself. Since I’ve been baking bread a bit, I decided to come away with some bread flour, buckwheat, spelt, and some polenta. I’ll let you know how it turns out.

The most interesting thing to me about the mill was how refined the design is. Our guide said that many of the elements for the mill would have been taken from the design published in The Young Mill-wright and Miller’s Guide, first published in 1795 (and available for download at the link!). Its author was Oliver Evans, who received an early (the third, apparently) U.S. patent for an automatic flour mill. It uses the power of water to move grist and grain around through a series of bucket elevators and conveyors. The mechanisms visible at the Bale mill seem rather antiquated to us today, but if one considers the times, they would have been positively cutting edge. The miller, working by himself (perhaps with some “dusties”, or apprentices), could have processed as much as a ton of grain per day. And since lanterns and the like were not allowed because of the risk of explosion, that was just as long as daylight lasted.

It was a lot of fun. If you are in Napa, consider stopping by (and donating money, they don’t receive any state funds anymore). I had a blast.

Like many people, I live in a development with a fairly restrictive HOA. This means that I have to be fairly careful to use largely invisible or stealth antenna setups. Because of a lack of suitable trees on my property, this means that I’ve had fairly compromised setups: I’ve gotten the most use from a simple 40m dipole which probably only averages about six meters in height.

But at least for receive there might be an interesting alternative. PA0RDT has developed a simple active antenna which has intrigued me.

Here is DL1DBC’s excellent description.

This article points out something which may not be entirely obvious until one thinks about it: antennas designed for transmission and reception have different goals. A transmitting antenna is designed for efficiency: to send as much of the input power out as radio energy as possible. In this context, short antennas have a very low radiation resistance, so other losses tend to dominate, and you lose a lot of power as heat. But receive antennas aren’t concerned with efficiency: you really just want to preserve the signal to noise ratio of the incoming signal. As long as the noise generated by the preamplifier is low, it doesn’t actually matter how efficient the antenna is. A short antenna picks up less of the desired signal, but also picks up less of the surrounding noise. So, these antennas can work reasonably well, especially on frequencies where full sized antennas are impractical such as VLF.

PA0RDT has created a simple preamp circuit, including a way to power the preamp through coax so you can easily mount this antenna remotely, say 50 feet from your house, and avoid the electrical noise that dominates many active antenna setups. A very neat solution, and inexpensive.

Some more links: Scott built one, using the more ubiquitous MPF102 and 2N3904 transistors, instead of the recommended but harder to find J310 and 2N5109 transistors.

Peter Marx got an official one that was built by it’s creator, Roelef Bakker:

You can read about Peter’s experience here.

A neat little project. Roelef’s articles (esp. the second one) linked from DL1DBC’s give lots of details. Worth looking at, particularly if you are interested in VLF/HF/shortwave listening.

In my previous post about the virtues of microcontrollers in homebrew radio, I had a comment from Lee, who mentioned that he operated a LowFer beacon on 187khz. I’ve been passively interested in LF operation under Part 15 rules for a long time, but haven’t really gotten involved with it much. Lee operates from La Crescenta, about 375 miles south of here by my estimate. He made this little video documenting his setup:

Pretty neat!

If you are interested, you can check out the Long Wave Club of America website to learn more about Part 15 operation. If any of my readers have any other up-to-date or interesting LF/MF part 15 links, I’d love to see them added to the comments.

As anyone who has followed my blog for any period of time knows, my interests straddle a lot of different disciplines and hobbies, and often find interesting bits of overlap where I find I can do cool stuff. Two of my favorite hobbies are tinkering with microcontrollers and with the low powered end of amateur radio, what we call “QRP radio”. A few of my previous projects (mostly related to beacons and sending automated Morse signals) have been in the overlap.

In the recent SolderSmoke Podcast #152, Bill, N2CQR recently took a tiny step into that overlap himself. He got himself Arduino, probably the most popular microcontroller platform, and used it to send out Morse, and then control an inexpensive DDS module to serve as a cool little VFO, complete with a rotary encoder to tune and a little LCD module to give the readout. Check it out:

Pretty darned cool. And both economical and useful. Bill was pretty sheepish about this tiny step into the digital world. In the past, he has expressed a greater comfort with radio circuits that are built from discrete components, such as diode mixers constructed with trifilar coils rather than the NE602 integrated circuits. After building radios with just a handful of discrete transistors, using even the simplest microcontroller which has tens of thousands (if not more) can seem like crass extravagance.

But I think he should cut himself some slack. Actually, not just cut himself some slack, but revel in the new direction his hobby has taken him.

In the strictest sense, QRP radio is just any communication which takes place with less than 5 watts of radiated power. But in the broader, more ideological sense, it means constructing radios which are simple, inexpensive and well optimized, without a surplus of useless features of whistles. There is a certain economy of design. When you look at VK3YE’s design for his “Beach 40” DSB rig, you have to marvel at the coolness of the design. Only 8 transistors, nicely documented in his videos. He draws the entire schematic out from memory while on the beach.

If your aesthetic finds this kind of circuit pleasing, the idea of injecting a microcontroller into the mix may seem like drawing telephone wires in the background of the Mona Lisa. But I’d submit that you can find aesthetic uses for microcontrollers in radios, even while being able to appreciate these great discrete, analog designs.

First of all, microcontrollers enable new and useful features. Even the simplest microcontroller can be used to send automated signals for things like QRSS beacons. Hans Summers super low power QRSS beacon can send a nice “shark fin” signal using only three transistors, but if you want to send your callsign, it rapidly becomes more difficult. Sure, you could strap a laptop or desktop computer to generate the modulating signal, but that seems very unaesthetic: hundreds of dollars and tens of watts of compute power just to drive a $5 transmitter with only a few milliwatts of output power? He actually sells a little preprogrammed microcontroller that will do the work, or you could get a K1EL keyer chip, but you are injecting a black box in your design, without any understanding or modifiability. But you could open that box up yourself. For the price of a pizza, you can get a dev board that will hook up to your laptop for programming, pull a few milliwatts of power, and dutifully key your transmitter. Once you get familiar with that kind of work, you can then make an embedded controller using just the raw chips: for instance, I have a few of these Atmel ATTINY85s that I got for $1.15 each (about the same as a 555 timer from our local Radio Shack) lying around for such applications. Add a crystal and two caps (or maybe even do away with the crystal, and use its internal oscillator) and your beacon becomes more flexible and more useful. Want to change the message? Have it send the current temperature or battery voltage as well? Piece of cake.

Second, microcontrollers are the easiest step into understanding computers. When I got my first computer back in 1980, it was already pretty difficult to understand the innermost workings of computers, although I did fairly master most aspects of my Atari 400. With modern desktops or laptops, it seems basically impossible. They have dozens of subsystems, with all sorts of interface and operating systems complexity. But these microcontrollers don’t have any operating systems, and because they are mostly self-contained, the total amount of stuff you have to learn is relatively limited. You tell the microcontroller to flip a voltage from low to high, and it does it, without drivers or intermediate layers. It allows the same kind visceral understanding and exploration that QRP is meant to stimulate.

Thirdly, just like the QRP community, it allows you to participate in a robust, vibrant community of experimenters. The people who are experimenting with Arduinos are kindred spirits to the homebrew radio enthusiasts. They want to take simple, cheap building blocks, and through the power of their understanding construct new, useful and novel applications. Even when their area of interests may differ from ours, you can learn from their skills and draw inspiration from their enthusiasm. And we might even find some potential hams in their ranks.

Don’t feel bad Bill: embrace your new digital skills. The more you goof around, the more applications you’ll find, and the more empowered you’ll be. Computers and QRP can co-exist, and even enhance each other.

Or not.

I find a lot of editorializing about amateur radio to be, well, curiously off the mark. For instance try checking out Dan, KB6NU’s well meaning article about why you should upgrade to a General. I mean, that’s what the title is: Why you should upgrade to a General. The reason I find this article so astounding is that despite the title, Dan doesn’t actually provide any reasons why you should upgrade to a General. The entire article presumes that whatever reasons you think you have for not upgrading, they aren’t valid. I find that a tiny bit presumptuous. But what’s really odd to me, is that there certainly are reasons to upgrade, he just didn’t bother to tell you any.

The most important difference (which underlies most of the others) is that you have access to spectrum which is unavailable to Technician class licensees. While Technician class licensees have all you can eat privileges above 50Mhz, they are pretty lean on the HF bands. With a General, you get full access to big hunks (but not all) of the spectrum below 6m, and this opens up a bunch of possibilities for communication. From SSB to RTTY to digital modes, you can participate more fully in the broad range of HF activity. The General exam is not a particularly difficult test, and you get a big bang for the buck. I’ve enjoyed WSPR, JT65 and beacon activity. And of course building and QRP operation. And just a lot of shortwave listening too (hey, no license required!)

But perhaps you don’t want to do any of that. Perhaps EMCOMM on VHF+ is your thing. Or maybe you like mountain-topping with 2m SSB. Or microwaves. Or APRS. Or D-Star. Or satellites. Or ATV. Or meteor scatter. Or EME. Or just hiking with an HT, or keeping in touch while on the road. I’m frankly okay with that, and I wish more hams were less concerned about what other people were doing, and simply got on with doing more of what they like in ham radio. Then, we wouldn’t have to scold and cajole people into upgrading: they would either be interested, or not. With the wide variety of interesting activity accessible to hams with Technician class licenses, it does not strain my credulity to think that it might be enough for someone.

When someone asks you why you don’t have your General or Extra class license, ask them how many moonbounce contacts they’ve made. If it is zero, urge them to upgrade their skills.

Previously, I have read about a wireless Morse thermometer designed by Steve Weber, KD1JV. I played around with the basic idea in a YouTube video I made. It basically powers a little Colpitts oscillator from an IO pin on an Arduino. Weber’s circuit did much the same, just using a small 8 pin AVR and a temperature sensor to send the current temperature via Morse code.

Over on the Open Emitter blog (sorry, don’t know whose blog this is) there is a twist on this basic idea: instead of using a separate oscillator, use the oscillator that drives the microcontroller as the emitter (probably of just a few microwatts into a short wire antenna). To on-off key the oscillator, the Atmel chip is put into power-down mode, and woken up via the watch dog timer. I think it’s a cool idea, and worthy of experimentation. I’ve got some ATTINY85 chips on sale (just $1.10 each) which will probably be breadboarded into a test circuit, using either some of my 10.140Mhz crystals or maybe some of the 80m or 20m crystals that I have lying around.

Check out the article:

Tiny Beacon

I’ve been busy lately, and have done almost nothing radio related. But John was kind enough to point out to me that Bill, N2CQR of Soldersmoke fame had posted a mention of me, and I surfed over to his blog to have a peek.

His post that apparently uses my code to send Morse which is tracked by the Reverse Beacon Network

Awesome. It’a actually pretty gratifying to see how often this simple (at least for me) code has been used and reused by people. I think of this code as being almost too trivial to worry about, but it’s clear that there are lots of people who are using the Arduino to try to get into some very simple code and electronics projects. I think that’s awesome! There are a number of authors/technocrats/philosophers who are saying that those who don’t learn to write programs are simply going to be left behind: appliance operators in life, and that those that do will be able to achieve. I don’t know that it’s true, but I do think some passing knowledge of programming can be leveraged into cool projects, and I’m glad to see that Bill has taken his first steps into the world of Arduino, and glad that I could be a part of it.

Addendum:

You can get my code from this blog post.

I made a couple of different videos using variations of this code. I was inspired to make this video after seeing Steve Weber’s “Temp2Morse” project, which basically keys a small oscillator powered directly from the pin of an ATTINY processor (in his case) or an Arduino in mine.

I used another variation of this code to interface a PS/2 keyboard to the Arduino, and then used it to key my FT-817:

(Apologies if you all have seen these before, but I thought they might be new to some of you.)

Tap… tap… tap… Is this thing still on?

Apologies to my loyal readers (reader?) for the lack of recent updates. A combination of work pressure, family visits, general lassitude and other distractions have caused the writing muse to flee, and every time I sit down to write something down, I have just felt physically tired and unable to write stuff down. But the good thing is: the days are getting longer, my project at work is shipping, and I’m hoping that May will mark the beginning of some good new projects.

Some things I have in the works:

• A number of Raspberry Pi related projects. In particular, I’ve got most of the parts for a little robotic platform that will carry a Raspberry Pi and a webcam. It’s my first real complete homebrew robotics project, which is kind of cool.
• I’ve been experimenting with 3D printing, and hope to do some more.
• Weather is improving, so the urge to get my RC airplanes back in the air.
• I need to get back to some radio projects. I was up to 43 states on my WAS via JT65, it would be great to polish that off this summer.

Stay tuned!

I lost 1.8 pounds this week.

I went on 2 mile walk with Carmen.

I soldered some clip leads onto pennies to make a touch sensor for the Arduino.

I figured out how to run the card deck on the Computer History Museum’s 1401 restoration page that computes pi on the 1401 simulator.

                                               000000003. * 10E-00000
  1415926535 8979323846 2643383279 5028841971 6939937510. * 10E-00050
  5820974944 5923078164 0628620899 8628034825 3421170679. * 10E-00100
  8214808651 3282306647 0938446095 5058223172 5359408128. * 10E-00150
  4811174502 8410270193 8521105559 6446229489 5493038196. * 10E-00200
  4428810975 6659334461 2847564823 3786783165 2712019091. * 10E-00250
  4564856692 3460348610 4543266482 1339360726 0249141273. * 10E-00300
  7245870066 0631558817 4881520920 9628292540 9171536436. * 10E-00350
  7892590360 0113305305 4882046652 1384146951 9415116094. * 10E-00400
  3305727036 5759591953 0921861173 8193261179 3105118548. * 10E-00450
  0744623799 6274956735 1885752724 8912279381 8301194912. * 10E-00500

We saw Life of Pi in 3D. Excellent.

I played too much minecraft.

I didn’t get enough sleep.