Nice DSA815 Upgrade

I know that quite a few of you are, like me, owners of the Rigol DSA815-TG. It's been a reliable workhorse in my lab since I've acquired it, but the one thing I believe that I've wanted to most from it is a an RBW minimum of 10 Hz instead of the specified 100 Hz. That would allow for better characterization of narrow filters like crystal ladder filters and would let you better see fine details about signal.

Well, it looks like today is our lucky day. I've received an email from Rigol that indicates that a new firmware update is available that will turn on 10 Hz RBW! Quoth Rigol:

Improved RBW -- We have improved the RBW spec on the popular DSA815 to 10Hz. This improvement provides users with greater frequency resolution and lower noise floor. 10Hz RBW is now specified on all of our DSA800 Series (1.5GHz, 3.2GHz, 7.5Ghz)

...

Existing DSA815 owners at 1.09 FW or above can upgrade to the latest 1.18 FW version to activate the 10 Hz capability.

Download new Firmware.

I believe that the link provided at the end of the email was a custom tracking URL for me, so I'll direct you to the Rigol NA DSA800 product page, which has a link for acquiring the latest firmware. Make sure that you are getting the 1.18 version of the firmware. The installation is a snap and the RBW improvement is an exciting new feature to get for free. Thanks Rigol!

Market Research

It has been awfully quiet on the public front here for sure, but I have been working on quite a bit of things behind the scenes here at Etherkit Galactic HQ. It's been a challenging year since I last wrote about the personal things going on here, but things have been going reasonable well after a rough half-year immediately following that post. I'm just about ready to attempt to revamp Etherkit, however there are still a few challenging roadblocks to overcome, and I could use a bit of guidance.

The most difficult issue is trying to re-bootstrap the business financially. I'm currently only selling the Si5351A Breakout Board, which obviously isn't enough to expand a business upon. The possibility of a capital infusion unfortunately broke down, and so the only practical way forward at this point is most likely another crowdfunding campaign.

As mentioned in the opening paragraph, I have been working on various projects, and so I do have some candidates. Many of the projects that are in the works or only even in the planning stages require the use of a microcontroller, and so last year I decided to make my own Arduino-compatible microcontroller board family which I can then use as the heart of many of these products. I've taken a real liking to the Arduino Zero because of its speed and features, but the cost is fairly high and the standard Arduino form factor isn't great for many purposes. Therefore, I have decided to make a new standalone board derived from the Zero which I call Empyrean, and you can see in the photo at the top of the post. It comes in two flavors: Alpha and Beta. The Alpha is based on the Atmel ATSAMD21G18A microcontroller, same as the Arduino Zero. The Beta uses a controller (ATSAMD21G16B) with a bit less flash and RAM than the Zero (but still more than an Arduino Uno), but is also priced similarly to the ATmega328 line of microcontrollers. Both come on a small board similar in size to the Nano and has nearly all of the same circuitry of the Arduino Zero except for the EDBG support.

It is true that there are a flood of Arduino clones out there and this makes entering the market with another one somewhat crazy. My value proposition for Empyrean is based on the confluence of breadboard-friendly form factor along with a wallet-friendly price. My target price point is around $15 for Alpha and $10 for Beta. While that is a fair bit more than your typical eBay Nano clone, Empyrean would also be quite a bit more powerful than a Nano, in both clock speed and available memory. So my question to you, dear reader, is whether you would be interested enough in this product to back a crowdfunding campaign in order to have it made? I do plan to make a serious push on a radio soon, but it would be nice to ramp up the business before that, while also solidifying the microcontroller platform that will be used in future products. Let me know what you think in the comments, or send me an email.

In the mean time, I thought I'd let you know that I'm working on a Rev D board spin of the Si5351A Breakout Board. You can see a prototype in beautiful OSHPark purple above. The most significant changes in this revision will be to change the coupling of the reference oscillator to the Si5351 XA input pin to meet datasheet specs and to panelize the board in preparation for future pick-and-place operations (they are currently hand-assembled!).

Perhaps even more interesting is that I also hope to be able to soon offer a frequency calibration report with every board sold. Thanks to LA3PNA, I am now in possession of a decent 10 MHz GPSDO to use as a lab reference, which will allow me to measure the frequency correction value accurately enough for hobbyist usage. I now have a small printer on hand, and so now what I need to do is add new code to my board test script to measure the correction value and print it for inclusion with each board sold. Stay tuned for notification when I'm ready to go live with this; hopefully soon.

Let me reiterate: I'd love to hear your thoughts about the above proposals. I'm interested in serving the needs of my customers. Thank you!

Break My New Library

I know that the updates here have been extremely sparse. For that I do apologize. Things are slowly starting to settle into a new normal around here, and I've been able to regain the ability to put time back into work. There's a large to do list on my whiteboard, and many of the things on that list depend on improvements and bug fixes to the Si5351 Arduino library. So that has been my first priority as I dip my toes back in the water.

There were quite a few features of the Si5351 that the older versions of the library did not support, such as all of the 8 outputs of the variants excluding the A3 and the VCXO of the B variant. Also, there is a pretty big bug in how the tuning algorithm handles multiple outputs assigned to the same PLL, which causes tuning errors to crop up.

Therefore, I decided in one fell swoop that I needed to totally rewrite the tuning algorithm and add support for as many of the neglected features as I could before moving on to other projects involving the Si5351. Over the last month, I've been hacking away on the code in my spare time, and I'm glad to finally be able to announce that a beta version of the Si5351 Arduino v2.0.0 library is ready for public use.

Because it's such a drastic change to the underlying code, I'd like to have it in limited beta release before doing a final release via the Arduino Library Manager. So that means that if you would like to try it (and I encourage you to do so), then you'll need to install it manually, which isn't terribly difficult.

Go here and click on the green button on the upper right that says "Clone or download". Select "Download ZIP". Next, find where on your filesystem your Arduino libraries folder resides and delete the existing "Etherkit Si5351" folder. Inside the ZIP file you just downloaded, there is a folder entitled "Si5351Arduino-libupdate". Unzip this folder into the Arduino libraries folder, and then restart the Arduino IDE.

Since this is a new major version release, I took the opportunity to tweak the interface a bit, which means that you'll have to adjust your current code to work with the new library (but fortunately not too much). You'll find the details on how to do that here.

Please check out the updated documentation on the GitHub page, as it has been greatly expanded and should explain all of the new features in detail. Also, quite a few new example sketches have been added to the library, which you can find in the usual place in the Arduino IDE. I encourage you to try the new library in your existing projects, as it should be a bit more streamlined and stable. Also, there is plenty of opportunity to make new projects with the B and C variant ICs. If you do encounter any problems with the new library version, I would like to strongly encourage you to use the Issues feature of GitHub to let me know so that I can get on to fixing it as soon as possible. When I'm satisfied that there are no big show-stopper bugs in the code, I'll merge it to the master branch of the repository and tag it for release via the Arduino Library Manager, but I need help in testing it before I can do that.

Once there's a stable release of this version of the library out in the wild, then I'll be able to move forward with other projects based on this Si5351. With any luck, some more interesting things will be coming from this shack again in the near future. Thank you for all of your help and support!

Edit: an exclusive look into the development process:

Linux Mint 18 Has Arrived

Those of you who have followed my blog for a while may be aware that our household has relied upon Linux for years. Earlier on, it was Ubuntu, and then later I migrated to Linux Mint shortly after the Unity environment was released for Ubuntu. I do have a dedicated Windows box for use in my Etherkit shipping station and I have dual-boot Win 10 on my notebook, but I only use Windows when forced. Otherwise, I much prefer Linux Mint, even on my ham shack PC.

Today is an exciting day for us Linux Mint fans, as the newest long-term support release, version 18 (code name "Sarah") has been officially released! Mint is derived from an Ubuntu LTS release, and the version 17 family was based on Ubuntu 14.04, which dates from 2014. Linux Mint 18 descends from Ubuntu 16.06, so there will be updates to the core software compared to version 17. (You can manually update most of these packages in an older release, but there's always a risk of corrupting your installation, so it's usually not worth it if you value stability).

Speaking of corrupting your system, I recently tried to update the kernel on my ham shack PC running Linux Mint 17.3 and messed up the system so bad it wouldn't even boot. Rather than try to spend the time doing a recovery, I decided to install the Linux Mint 18 beta last week and give it a spin. My initial impressions from working with it over the last week are very positive. The shack PC is very modest, using a cheap AMD Athlon 5350 APU (I guess that's their name for their integrated CPU/GPU/SoC) with integrated Radeon graphics. Under Mint 17.3, the Radeon graphic support was kind of terrible. The proprietary fglrx driver kind of worked but was glitchy as hell and the open-source driver had absolutely terrible performance. Under Mint 18 with the newer AMD open source graphics drivers, the machine performs as expected, which is a relief. The Mint-Y theme looks fantastic, and I think I much prefer it over the default Mint-X.

Linux has truly come a long way on the desktop. If you are a Windows user who has dabbled in Linux previously but found it a pain to get working, you should try Linux Mint 18 on live OS installation to see how far it has come. Much more "plug-and-play" than just a few years ago. Grab that ISO torrent, image it to a USB drive, and give it a whirl!

Wideband Transmission #9

Arduino in the Cloud

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I saw a recent post on the Make blog about the new cloud ecosystem for Arduino which has been dubbed Arduino Create. Since this will most likely be the future of Arduino, it seemed wise to get an early look at the platform. It includes quite a few features, but the most notable ones in my opinion are the Project Hub, Arduino Cloud (IoT infrastructure), and Web Editor. Arduino Cloud will allow you to connect your network-capable Arduino to the Internet to allow sharing of sensor data, remote control over the net; your typical IoT applications. The Web Editor gives you access to an Arduino IDE over the web. Your code is stored online, and a cloud compiler builds your project, so you don't have to worry about configuring that on your machine. However, you still have to install an OS-specific agent program on your PC in order to get the complied firmware from the Web Editor onto the Arduino's flash memory. The Project Hub is a project-sharing space, similar to hackaday.io, Instructables, etc.

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I don't have much to comment on regarding Arduino Cloud, since I don't have any of the supported devices and cannot try it out at this time. The Web Editor gives me mixed feelings for sure. No doubt that this was created to compete with the mbed platform, which sounds awfully convenient from what I have seen. I like the idea of being able to easily save and share code with others, as well as having a standard set of build tools for everyone. However, the environment is obviously still in early stages, as there is no support for libraries to be added through the official Library Manager JSON list, nor for external hardware definition files to be used. I had some difficulties getting the Arudino Create Agent talking to my web browser in Linux Mint, and once I did, uploading seemed a bit flakier than it does on the desktop IDE. Of course, this is all still in beta, so rough edges are to be expected. Once they get the features of the Web Editor up to parity with the desktop IDE, it should be a very useful tool. Finally, the Project Hub looks nice, but I wonder if we aren't starting to see too much fragmentation in this type of service for it to be useful. Still, the one-stop shopping aspect of it all is very spiffy.

Something to Watch

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Ham radio seems like a natural fit with the citizen scientist movement, so it pleases me to have discovered that some hams have created a platform to advance citizen science in an area where we are well equipped to do so. The new HamSCI website states its mission as:

HamSCI, the Ham Radio Science Citizen Investigation, is a platform for the publicity and promotion of projects that are consistent with the following objectives:

  • Advance scientific research and understanding through amateur radio activities.
  • Encourage the development of new technologies to support this research.
  • Provide educational opportunities for the amateur community and the general public.

HamSCI serves as a means for fostering collaborations between professional researchers and amateur radio operators. It assists in developing and maintaining standards and agreements between all people and organizations involved. HamSCI is not an operations or funding program, nor is it a supervisory organization. HamSCI does not perform research on its own. Rather, it supports other research programs, such as those funded by organizatons[sic] like the United States National Science Foundation.

They already have three listed projects that they are helping with: the 2017 Total Solar Eclipse, ePOP CASSIOPE Experiment, and Ionospheric Response to Solar Flares. The 2017 eclipse is of special interest to me, as totality will be seen at latitude 45°N here in Oregon, which puts it squarely over Salem; a place I will have easy access from which to observe (which also reminds me that I need to build some kind of solar observation device like the Sun Gun before August 2017).

I wish these folks the best and I hope they are able to make a useful contribution to science.

A Challenger Appears

A EEVBlog video popped into my YouTube feed yesterday that was of significant interest to me, and will probably be to you as well. Most of us who are into having a home test & measurement lab are well aware that the Rigol DSA-815 has been the king of spectrum analyzers for the last few years, due to the very reasonable cost paired with the decent amount of bandwidth and load of useful features that are included. Rigol seemed to own this market space since the DSA-815 was released, as the big boys of T&M didn't seem to care too much about serving us little guys with our small budgets. However, those days are probably at an end, as a new SA to rival the DSA-815 is on the cusp of release. Dave Jones gives a cursory review of the new Siglent SSA3021X, which looks like it will cost only a few hundred dollars more than the DSA-815 but may be significantly better in the performance category. I'd recommend watching the video below, but here's a summary of the points that interested me:

  • User interface seems to be heavily "inspired" by the Rigol DSA-815
  • The Siglent has significantly better DANL
  • 10 Hz RBW available on the Siglent vs 100 Hz on the Rigol (I've seen hints that the Rigol was supposed to have a 10 Hz RBW option, but they never released it)
  • Reference clock and PLL in the Siglent look better
  • The Siglent has a waterfall display available, which is missing from the Rigol
  • Dave spotted some potential unwanted spurious signals in the Siglent, but they were low level and his machine wasn't a release version either.

Also, don't miss Dave Jones in typical Dave Jones-style refer to a signal with unwanted sidebands as a "dick and balls".

My impression is that if Siglent can tighten up the fit and finish of this spectrum analyzer, it could give the DSA-815 a real run for its money. This is nothing but good news, as more competition in this space will mean even better products for us in the future. I'll be watching this one.

Fun with Marbles & Magnets

Finally as a palate cleanser, enjoy this clever kinetic artwork contraption built to play with marbles and magnets!

 

TDS1012 LED Backlight Retrofit

Back when I was working at Tektronix (wow, this summer it's been 10 years since I graduated with a AAS in EET and started at Tek), they had a one-time program where an employee could purchase a new TDS1000/2000 series oscilloscope for half of the list price. This was back in the day before the era of cheap and decent Chinese-manufactured scopes, so naturally I jumped on the deal. Even though I wanted more, I found that I could fit the TDS1012 into my budget (list price was a bit more than $1000 at that time).

The TDS1012 was a very faithful instrument on my bench for many years. I came to depend on it quite heavily. Too heavily, in fact, as I left it on a lot. Not thinking about the ramifications of it at the time. A few years ago, the backlight in the scope started fading, and not long after that, gave out completely. I figured I could just replace the display module, but finding a replacement turned out to be more difficult than I anticipated. Tektronix repair didn't stock it by the time that I inquired about it, and I could not find any through the back-channels that I checked with my Tektronix contacts. Even looking for NOS on eBay was fruitless (although later on, some grey market displays started turning up there for expensive list prices).

TDS1012-2

Eventually I gave up hope of realistically finding a replacement display and tried to sell the scope, although not very enthusiastically. The scope stayed in this state for quite a while, until I found something fortuitous. One of my favorite vlogs is The Signal Path, and Shahriar recently released a short video about repairing an VNA with a broken CCFL backlight with a LED replacement.

I'm not sure why it never occurred to me to try this, but I was grateful to have seen a path forward with the TDS1012. I didn't even know that there existed LED backlight upgrade kits, but I shouldn't have been surprised. Long story short, I ordered a handful of parts from eBay and took a chance, and was rewarded with a working display that was able to bring my beloved TDS1012 back from the dead! I'll give you some details below so that hopefully this can be of help to others in the future.

Bill of Materials

LED Backlight Upgrade Kit (there's a wide variety of these available on eBay)

s-l1600

XL6009 DC-DC Boost Converter

s-l1600 (1)

5 kΩ trimmer potentiometer
4.7 kΩ resistor, 0.25 W
Kapton tape
RTV silicone
Epoxy

The Details

The first thing to do was disassemble the TDS1012 so that I could get to the guts. Fortunately, I had done this in the past, so I knew exactly what to do. It's actually quite easy to do in the home lab with just two tools: a deep Torx T15 screwdriver and a small pair of hook-nosed tweezers. Pry off the knobs on the front panel by wedging the hook-nosed tweezers in the gap between the knob and panel, and then using them as a lever.

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Remove the back case from the instrument by unscrewing four T15 screws: one on the bottom-left, one on the bottom-right near the AC power connector, and two hidden under the fold-up handle.

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Next, the front panel can be removed by unscrewing five T15 screws: one on each corner and one hard-to-find screw that is between the CH1 and CH2 BNC connectors (on the back of the chassis). You can see side where those screws need to be removed from the chassis in the photo above.

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Once the front panel is off, you can now remove the display module. There are two cables to disconnect: the CCFL backlight cable going to the HV supply, which is on the top-left of the above photo, and the data cable which is on the right side (unseen in the above photo). Disconnect the CCFL cable and the data cable from the main board, and then remove the four T15 screws from the four corners.

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Now with the display module removed, you can see where the CCFL lives on the left side, under the beige plastic. I removed the Kapton tape securing the CCFL leads to the module, and then tried to pry the plastic apart at what looked to be interlocking snap tabs.

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That turned out to be a bit of a mistake. The plastic was quite brittle and broke on the back side, including a few fragments from each end that snapped off completely. I think I should have removed that tiny screw that you can see on the center-left of the front of the display module before trying to take the CCFL out.

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There is some metallic foil that loops around the CCFL. I used a craft knife to slit it down the length of the display, freeing the CCFL from the module.

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You can see the burned-out CCFL in the photo above, removed from the display module. Now that the defective part was removed, it was time to figure out how to rig up the new LED backlight.

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Here you can see the LED module as packed by the seller. I was pleasantly surprised. Quite nice and secure.

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And here is the LED kit. This kit was made for a 15 inch monitor, so I would only need part of the LED strip. As was the case with other LED strips I've used, this module was wired so that groups of three LEDs were in series, with each of those groups in parallel with each other. I cut the LED strip at a multiple of three at a size that would fit where the CCFL used to live. Be very careful with this strip, as it is quite fragile and could easily break at the length it is shipped (which I'm sure it why the seller packaged it so well).

Next, I lashed up the LED driver module on the breadboard to see how it should be wired. As is common with these eBay modules, the documentation is pretty lacking, so I had to put in a bit of work to make sure I got the wiring right. There are four input pins on this module: VCC, GND, ENB (enable), and DM (dim). A bit of experimentation showed me that you needed to tie ENB to VCC and that DM could be fed using a simple voltage divider with a trimmer and fixed resistor to provide an adjustable voltage to DM that ranged from about 0.5 VCC to VCC.

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The product page recommends that the DC input be at least 10 VDC, and when driving it with >11 VDC the LEDs were quite bright. Any voltage below about 9 VDC, and the LED just won't light. In a lot of instruments, that may not be a big deal, but it was a problem with the TDS1012. It turns out there is no 12 VDC available, nor anything even close. The only other appropriate DC voltages available from the power supply are 6 VDC and 3.3 VDC. But the module just won't run on a voltage that low. I identified the IC on the LED driver module to be a DF6113. By the looks of the datasheet, it should be able to function as both a boost converter and constant current source for the LEDs, but this particular module will not run at 6 VDC.

A bit of half-hearted reverse-engineering showed me that while the DF6113 has the capability to function as a boost converter, that functionality was not being used here. In the reference design on the datasheet, it shows it being used as a boost converter with an LED output which is ground-referenced. However from what I could suss out of the eBay module, this one was configured to not be ground-referenced. Instead, the lower potential terminal of the LED driver was set at approximately 9 VDC lower than the input voltage, hence the reason why it would not function below 9 VDC input.

Rather than try to hack this module, I figured it would be easier to purchase a DC-DC boost converter module off of eBay from a US seller. After a few days, I had a XL6009-based module in hand, which looks to have a wide range of usable input and output voltages, and can easily source enough current to drive a small strip of LEDs. With the plan to drive the boost converter from the 6 VDC rail available from the TDS1012 power supply board, I set my bench supply to supply 6 VDC to the boost converter, set the boost converter to supply 12 VDC to the LED driver, and managed to get everything set up to light that LED strip from 6 VDC input. I just had to hope that the power supply had enough current margin for this LED strip, plus the losses in the boost converter and driver board.

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Now that the LED has been verified to work correctly, it was time to fit it into the display module in the place where the CCFL used to be. With the CCFL removed, you can peer down into the cavity it has left behind and see the glass panel that diffuses the backlight. The LED strip was placed facing into the edge of this glass so that the terminals came out of the top of the module (where the old CCFL wiring ran), and I used RTV silicone to secure it in place. I chose RTV silicone for two reasons: it would be easy to remove if I messed up the placement of the LEDs and it would be reasonably transparent if I got some adhesive in between the LEDs and the glass. It appears that was a good choice.

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Now I used epoxy (the cheap stuff from Harbor Freight) to seal up the plastic cover that I cracked earlier, mainly to provide mechanical stability and extra protection to the LED strip.

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Once that was dried, I lashed everything up to breadboarded driver circuitry to ensure that the backlight was actually do the job. As you can see above, it looked good so far!

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The real acid test for me was to see if the TDS1012 could actually drive the new backlight from its own power supply. I really had no idea if the current budget was there in the instrument, as there weren't enough details in the service manual to know. So I had to just lash it together to try. The boost converter was soldered into the 6 VDC and GND terminals on the J9 connector on the power supply board, and then power was applied to check for magic smoke. Nope, success! BTW, if you are replicating this test, be sure to plug all of the modules together, as the instrument won't power up unless all of the cables are connected.

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Now the job was to stuff the boost converter, trimmer pot, and LED driver module into the existing chassis so that it was secure and safe. The modules were test fitted into spaces where they looked like they would conveniently fit, and then Kapton tape was generously laid down on the chassis to give them a safe mounting point.

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Fortunately, both of the modules were small enough to fit quite nicely in existing space, and both were single-sided boards, which meant that they could sit flush against the Kapton tape easily. The modules and pot were secured in place using more of that epoxy (although hot glue would have probably also worked well).

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The leads to the LED strip were routed back through the hole in chassis where the old CCFL leads went, and easily were able to reach the new LED driver module. After that, it was a simple matter to reassemble the instrument and power it on for a final smoke check.

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It works!

Although not the most skillful of hacks, it's always quite satisfying to recover something of value from the scrap heap with a handful of parts (about $15 worth in this particular case). I think the new LED backlight is actually brighter than the old CCFL backlight, but it has been a while since I've seen it with the original backlight, so that's a pretty poor subjective observation on my part.

One small warning here: I have only done rudimentary checks to see what effect the DC-DC boost converter would have on the measurements from the scope. I don't see any obvious hash from the switching power supply on the most sensitive vertical setting, but it's possible that the this might introduce some low-level unwanted spurious into the instrument, which perhaps may be visible when using the FFT function. Caveat emptor. You have been warned.

So for those of you with older instruments with busted CCFL backlights, I would highly suggest that you can retrofit a new LED backlight if you have some moderate electronics skills. There's nothing particularly magical here. The biggest concern is whether you can pull enough current from the existing DC power supply, but I imagine most instruments have power supplies that are designed to easily give up enough extra current to power a small LED strip without and difficulty. And if you have an instrument with 12 to 24 VDC already available, you can skip the boost converter that I had to use and not even have to worry about that. Give it a try and give some old junk new life!

Nerd Famous

It's nice to see we hams, who I think suffer from a bit of an image as throwbacks in the larger maker community, get some recognition for the good stuff we've accomplished. Today on Hackaday, a nice article about Manhattan and Ugly construction was posted, with ample coverage given to the fact that a lot of the best exemplars of these techniques come from the world of amateur radio builders. I'm not certain about how others feel on this topic, but it seems to me that Hackaday is one of the preeminent blogs relating to our hobby, so I get quite excited when we get repped there.

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Featured in this article are two names well-known in our circles, and guys that I'm proud to call my friends (although I have never personally met either in real life yet!). Todd VE7BPO, is renowned for his rigorous empirical work in circuit design, as well as his beautiful Ugly circuit creations. They feature one of his designs near the top of the article.

hackaday.com-2016-05-04-getting-ugly-dead-bugs-and-going-to-manhattan-_105

The other is Dave AA7EE, who is probably familiar to almost every reader, unless you just crawled out from living under a rock for the last decade. It's not difficult to see why they chose Dave's work for to illustrate Manhattan construction, as his is some of the best out there. Period. Also unsurprisingly, this is not the first time that Dave's creations have made it to Hackaday.

Well done, gentlemen! Way to show the maker world at large that we've got relevant skills for the 21st century hacker community!

 

Wideband Transmission #8

Another 10 mW WSPR Beacon

I enjoy writing up my projects, but it's much better to get feedback to see that someone was actually able to take my writing and successfully duplicate my project. Via the Etherkit Twitter account, I received this from Tom Hall, AK2B regarding my last posted project:

Awesome work! Tom has been a great supporter of Etherkit from the beginning and I'd like to thank him for sharing his neat creations with the rest of us. It's wonderful to see such a minimalist design perform so well!

More Coding Resources for Fun

I haven't had a ton of free time here, but I do get snippets of time occasionally where I can sit with my notebook PC for a bit and mess around. As mentioned in some recent posts, I've been revisiting coding for fun, and I've stumbled upon quite a bit of new resources that are new to me and that I thought would be good to share.

The first one I'd like to mention is called Scratchapixel. I was curious about the mathematical methods behind 3D rendering, and some searching brought me to this exhaustive tutorial site. It's not 100% complete yet, but most of the fundamentals of 3D graphics are already well-explained there. A fantastic resource if you are curious about the first principles of 3D rendering like me.

A related site is called Shadertoy. Not by the same people, but also related to the topic of learning 3D programming. Shadertoy is a web application that lets you play with shaders in C++ inside a web IDE that can be updated on-the-fly. It takes a bit of CPU and graphics horsepower to run comfortably, but if you've got the capacity, it's worth browsing the demos on the site just to see the cool stuff you can create with it. This tool was created by Íñigo Quílez, who also has a really cool home page with lots of tutorials and whitepapers. If you like demoscene stuff, then definitely check it out.

Another neat find that I only recently discovered goes by the name of Rosetta Code. It bills itself as a programming chrestomathy site, which basically means that it's a way to learn how programming languages are related in a comparative way. There is a large directory of different programming tasks, and each task page lists ways to implement a solution in a wide variety of languages. It's a wiki, so not every page has every language implementation, but there's obviously a ton of work put into the site, and most tasks have implementation in the major languages. Really fascinating and useful at the same time.

Finally, there's The Nature of Code. This site hosts a free e-book download of the content, and provides a link to purchase a dead tree version if you wish. Here's how the website describes the book:

How can we capture the unpredictable evolutionary and emergent properties of nature in software? How can understanding the mathematical principles behind our physical world help us to create digital worlds? This book focuses on the programming strategies and techniques behind computer simulations of natural systems using Processing.

That sounds right up my alley. I haven't read the book yet, but I have skimmed it a bit, and it looks like the kind of things that I love: non-linear systems, physics simulations, fractals, and the like. When things settle down here a bit, I may tackle the book and re-write the sample code into Python. That would give me some more Python practice and force me to really think about the algorithms behind the text, not just blindly copying, pasting, and executing the scripts.

Let me know in the comments if you found any of these links useful or fascinating, or better yet if you know of other links in the same vein.

New Miles-Per-Watt Record Opportunity?

If you regularly follow science news, you may have heard of the Breakthrough Starshot initiative. In short, this is a study to create pathfinding technology that would allow the eventual launch of micro-lightsails with tiny mass to the Alpha Centauri system at a significant velocity (0.2c!) with a ground-based laser array. It's probably a serious effort, as it is being privately funded to the tune of a whopping $100,000,000. No doubt, an extremely audacious undertaking.

Sounds interesting, but what does this have to do with radio? Well, obviously there's the issue of how you can get a usable signal back to Earth across a distance of 4-and-a-half lightyears from a craft that masses in 10s of grams. I was wondering about that exact engineering challenge when I came across this article in my feed reader today. It turns out that someone has studied how one might use the Sun as a gravitational lens for lightwave communication across interstellar distances. Claudio Maccone, an Italian physicist, has run an analysis and has determined that putting a receiver at distance of at least 550 AU from Sol will give the desired lensing effect for optical communications.

Speaking before Maccone at the Breakthrough Discuss meeting, Slava Turyshev (Caltech) pointed out that the gain for optical radiation through a FOCAL mission is 1011, a gain that oscillates but increases as you go further from the lens. This gives us the opportunity to consider multi-pixel imaging of exoplanets before we ever send missions to them.

That's kind of amazing. Maccone calculates that the bit error rate of optical communication from at any significant distance from Sol quickly degrades to around 0.5. However, by using the Sun as a lens, the BER stays at 0 out to a distance of 9 LY. Here is a graph of the effect of standard comms and those enhanced by using the Sun as a gravitational lens, as calculated by Maccone:

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What's really crazy is this next paragraph:

But as Maccone told the crowd at Stanford, we do much better still if we set up a bridge with not one but two FOCAL missions. Put one at the gravitational lens of the Sun, the other at the lens of the other star. At this point, things get wild. The minimum transmitted power drops to less than 10-4 watts. You’re reading that right — one-tenth of a milliwatt is enough to create error-free communications between the Sun and Alpha Centauri through two FOCAL antennas. Maccone’s paper assumes two 12-meter FOCAL antennas. StarShot envisions using its somewhat smaller sail as the antenna, a goal given impetus by these numbers.

So that would have to rate as the ultimate QRP DX, eh? I'm not sure how realistic any of this is, but I'm pretty sure the physics are well-established by now. Kind of makes the Elser-Mathes Cup look like small potatoes.

 

SOTA After Action Report - Sheridan Peak

Thanks to the efforts of Etienne Scott, K7ATN, we who live in the Pacific Northwest have a couple of nice SOTA summit-to-summit activity days each year. One that happens in early spring and if I remember correctly the other which occurs later in the summer. I participated in the spring S2S Party two years ago, but haven't had a SOTA activation since.

As mentioned in a previous post, things have been kind of crazy here lately, and Jennifer has been encouraging me to get out to do something I enjoy, so I decided to take this Saturday to participate in the S2S Party. I was considering Bald Peak, which is just on the outskirts of the Beaverton-Hillsboro area, and makes for a quick and easy trip, but by the time that I went to Sotawatch to claim it, I noticed that K7ATN had already done so. Thanks to SOTA Maps, I was able to easily browse some other peaks relatively close, and settled on Sheridan Peak, especially since a previous trip report tagged it as a fairly easy drive and hike.

I needed a travelling companion, so I asked my 5-year-old son Noah if he wanted to go, and he eagerly agreed. I wasn't sure if that enthusiasm would hold up during the trip, but at least because of the short hike to the summit, it would be easy to bail out if necessary. So we departed the house at around 9 AM, stopped by McDonalds for a light breakfast and a large coffee for me, then took the backroads of Washington and Yamhill Counties out to Sheridan Peak.

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The drive was uneventful, other than my phone's GPS getting a bit lost at the very end of the trip. However, the driving directions from the two previous write-ups of this peak on pnwsota.org were great and got me right to the parking lot. Actually, the gate to the parking lot was closed, but that was OK because there is a nice big turnout on the road immediately below it, so we just parked there and walked around the closed gate.

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The hike up to the summit was quite easy, and Noah did well for one of his first actual hikes. Unsurprisingly for a peak in the Oregon Coast Range, the weather was damp and showery. Although we didn't have much of a view from the top due to the forest, one big advantage of that was the canopy over our heads providing a bit of a break from the rain.

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Fortunately, I was prepared for the rain, and I quickly erected a tarp shelter for us to use to take cover from the elements. It was actually fairly cozy under the shelter, as another advantage of the tree cover was that it was acting as a nice wind break from the usual chilly blast you get on a peak.

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I don't currently own any HF portable gear, but thanks to the generosity of W8NF, I was able to borrow a Yaesu FT-817 and Elecraft T1 tuner. A few days prior to the activation, I cut a random wire and counterpoise that would at least work on 40 and 20 meters, and tested it in my backyard. That turned out to be a good thing, as I was able to get my wire in the tree and get the 817 QRV with no problems at all. I also brought along my Baofeng UV-5R with rubber duck/tiger tail combo for 2 meter FM ops, with the 817 as the designated backup if that didn't work.

At the designated time of noon local, I heard K7ATN full quieting on 2 meters (which wasn't a huge shock, as his peak was only about 20 miles away from mine). There wasn't a huge turnout for this activity day like there was a few years ago when I did it on Cooper Mountain, but I did manage to make four S2S QSOs on 2 meter FM with the UV-5R in order to officially activate the peak. Woo! After that, I switched to 40 meters LSB on the 817 and made a couple of S2S QSOs with stations that I had already talked to on 2 meters and one with a local chaser. Finally, I had K7ATN spot me on 20 meters and managed to squeak out a couple more SSB QRP QSOs, both with stations in Arizona. By then, Noah was getting a bit cold and wanted to get going, but I was pretty happy with the results. From the sounds of things on 2 meters, a few of the other activators had some pretty crummy weather conditions to deal with, especially NS7P on Mary's Peak.

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So after about an hour on the peak, Noah and I packed everything up and headed back down the half mile or so to the pickup. I was very proud of Noah, as he did great for a 5-year-old; never really complaining and obviously really enjoying being out in nature, plus I think he liked the radio activity as well.

I'm really happy to have made this activation, especially since I was able to get Noah involved in both an activity out in nature plus radio fun! Thanks again to K7ATN for all of the hard work that you put into the PNW SOTA community and the rest of the activators for getting out there in this wet spring Oregon day. Stay tuned for hopefully one or two more SOTA activations this year, hopefully with more family members coming along on future trips.

Edit: Here's a recap of the event from K7ATN.

200,000 Miles Per Watt

If you wouldn't mind, I would like to draw your attention to my latest post on the Etherkit App Notes blog. In it, I detail how to create a 10 milliwatt WSPR beacon using nothing more than the Etherkit Si5351A Breakout Board, an Internet-connected PC, and a low-pass filter. A simple project, but one that gives quite a bit of fun testing the ionosphere given the cost and complexity.

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I don't want to take away from the post, so I will advise you to go there to read it, but the bottom line is that with about 10 mW, I was able to get a signal decoded over 2000 miles away. I remember reading the old exploits of the QRPp gang in books like QRP Power, where you had to be really dedicated, organized, and good at decoding CW in the worst conditions. Now, we have the luxury of a mode like WSPR, which lets us do milliwatt propagation experiments without breaking a sweat.

One idle thought I had about this is whether it would be feasible to put this transmitter on the 13 MHz HiFER band (check out Dave AA7EE's excellent treatment on the matter) and whether that would be something that would be fun and useful for schoolkids to experiment with. Of course, it's technically feasible, but I would want to be sure that 1) it's legal and 2) there would be interest in doing it. A single PCB could be made with one Si5351A output attenuated to around 4.6 mW and low-pass filtered for transmit, while another output could be used to drive a simple fixed-frequency receiver based on the SA612. Let me know what you think about this in the comments.