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!

 

Quick Impressions of the Rigol DSA815-TG

Needing to upgrade my spectrum analysis capability, I recently sold my trusty boatanchor HP 8558B to help finance a portion of a new Rigol DSA815-TG spectrum analyzer. Last week I was able to order the 815, and today it finally showed up on my doorstep. I first came across the 815 last year, at the 2012 Dayton Hamvention. I believe that it had just been released at that time, and I don't recall hearing any buzz in the ham radio world about it. I was very intrigued by it, and vowed to look into it further. A bit later, videos of the 815 in operation started showing up on YouTube, which got me even more intrigued (there's lots of very good, detailed videos available via search). The final nail in the coffin was the product review in a recent issue of QST, which was quite favorable.

A quick overview of the banner specs include a 1.5 GHz bandwidth, standard preamp, DANL of -135 dBm, 100 Hz minimum RBW, and the -TG option includes a built-in 1.5 GHz tracking generator (an absolute must-buy). It comes in a compact, yet solid, portable enclosure; about the size of a larger portable oscilloscope. The LCD display is clear, ample, and well-backlit. The unit also has a nice variety of connectivity, including LAN, USB host, and USB device, as well as 10 MHz reference in and out.

I had a chance to briefly run it through some measurements this evening, which I'll share with you below.

This first image is a capture of a local FM broadcast station on 100.3 MHz. You can see the standard FM modulation, along with the very blocky digital HD radio subcarrier.

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The next capture is a tracking generator sweep of a narrow CW filter that I had lying in my junkbox. It only has 3 crystals, which you can tell by the fairly shallow skirts. I was concerned that the 100 Hz minimum RBW might be too limiting for measuring narrow CW filters, but by all appearances it seems to do a good job in conjunction with the tracking generator. You can also see the very handy automatic 3 dB bandwidth marker measurement, which makes the process quick and simple.

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Here's a sweep of a 6-crystal SSB filter that I also found in my junkbox. Again, you can see how useful the 815 can be with this type of measurement. It only takes a few moments to get this result once you get familiar with the basic functions of the 815.

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Finally, I paired the 815 with a homebrewed return-loss bridge so that I could make a wideband sweep of my main station ZS6BKW antenna. Here you can see return loss plot from 2 to 30 MHz. The resonances in the ham bands are quite obvious (some are indicated with markers). I never did any trimming on the antenna since I use it with an autotuner, but you can see that it came in pretty closely on the first try.

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Only having used the 815 for a few hours, I'm already quite addicted to it. It's going to be a hugely useful addition to my stable of test equipment. I'm sure you'll see many measurements from the 815 in the years to come on this blog.

HNY

Yes, a belated Happy New Year greetings! It's hard to believe that 2013 is already well under way. I figured it was about time to give you a quick update on what's going on in the shack right now.

First up is the discrete component grabber receiver for 14.141 MHz that I prototyped to be paired with the OpenBeaconMini project. The receiver itself consists of a roughly 2 kHz wide crystal filter on the front end, feeding into a single-balanced diode ring mixer, which drives an AF amp using 2N4401 and 2N4403 transistors. Because I'm not able to put up a proper outdoor antenna for the grabber right now, I decided to put the VE7BPO cascode active antenna on it instead. It seems to work well, but I don't know for sure because there are basically no signals on this part of the band. I intended to use my Raspberry Pi with the receiver as a grabber, but I had no luck getting either LOPORA or QRSSVD to work properly and reliably. It may just be asking too much of the poor beast. So I'm going to try to appropriate another PC in order to get the grabber receiver QRV so that on-air testing of OpenBeaconMini can begin in earnest.

Discrete component monitor RX for 14.141 MHz
Discrete component monitor RX for 14.141 MHz

Next, I wanted to give you a very brief overview of my most recent purchase for the lab: a Rigol DS1022U arbitrary waveform generator. As far as I can tell, this appears to be pretty much the same as the DS1022A model that is sold in the US. But being a typical ham, I wanted to save a few dollars, so I purchased it off of eBay from seller who says he is an authorized Rigol dealer.

Rigol DG1022U Arbitrary Waveform Generator
Rigol DG1022U Arbitrary Waveform Generator

The DG1022[U|A] has two channels that can output a sine wave up to 25 MHz in 1 mHz (as in millihertz) steps. It can also provide square, ramp, pulse, noise, and arbitrary waveforms at lesser frequencies. It can modulate the waveform in a variety of ways, including AM, FM, PM, PWM, and FSK. It can, of course, also do sweeps of various parameters. The output amplitude into 50 Ω ranges from 10 Vpp on Channel 1 or 3 Vpp on Channel 2 down to 2 mVpp on both channels (or -50 dBm). The shielding on this AWG seems to be excellent. Using my HP 355C/355D attenuator combo, I can get a signal down to about -140 dBm (disclaimer: not a scientific measurement, made using my ear as a detector and listening on my IC-718). The dual outputs makes it very useful for a variety of two-tone receiver measurements, one of the big reasons driving my purchase. The Channel 2 output also doubles as a 200 MHz frequency counter input. Paired with the USB connectivity of the device (it seems to enumerate as a usbtmc device), that will be extremely handy for measuring oscillator drift. The DG1022 can also link the two channels together and give them a specific phase difference, as you can see below. This will make it very handy as a I/Q LO when I want to experiment with phasing and SDR rigs.

I/Q Output from DG1022U

So far, I've been very pleased with my purchase. I don't feel like I've had it or used it long enough to give you a full review, but I thought that this preview would at least be a bit helpful for those thinking about using it. One of my goals for the new year is to do a much better job of characterizing everything that I build. Since I intend to start selling transceivers in the near future, it's doubly-important that I can make accurate measurements of my products so that I can properly state their specifications. To this end, I've decided to sell off a bunch of my unused or replaceable test equipment (please take a look at the for sale posting) in order to finance the new, calibrated test gear. Next up on my purchase list is a Rigol DSA815TG spectrum analyzer (just reviewed favorably in the February 2013 QST), but that's going to require the sale of everything on that page!

Finally, I've got the CC1 prototype PCBs on their way from Seeed Studio right now. It looks like they just cleared customs in the US, so hopefully they will be in my hands in the next few days. With any luck, I'll have the first one built by the weekend and will be well on the way to a new beta test. I'll put up a quick post to show off the PCBs, and when the first prototype unit is completed. Stay tuned!