Raspberry/Beagle/Core Benchmarks

Measured the other day using iPython:

iPython's "timeit" function is hardly the last word in benchmarking, but it can be very useful if you're thinking about Python applications.  Raspberry Pi is very powerful compared to Arduino, say, but very slow compared to modern desktop machines.   No surprises, but I haven't seen relative benchmarks before.

Lousy Saturday on 40 meters

Solar weather (M class flare) makes the low HF bands very quiet this morning! Some day I have to dig in and understand the scale on this map.  It says we're affected by "1 dB" on 40 meters, but I'd say it's more like 30 dB from listening on the band.

Check http://www.swpc.noaa.gov/drap/global.html for the latest.

Raspberry Pi - 30X more time for coffee

alliedelec.com

My Raspberry Pi is benchmarking about 30X slower than one thread (out of 8) on my desktop Core i7 processor. It's an interesting challenge to do real-time Python / wxWidgets programming on the little guy, but we're making progress.

Cable to U-Verse and back again

Executive summary: AT&T U-Verse out, Comcast cable in.

I've been living as an Amateur Radio operator with AT&T's U-Verse service for about 18 months.  It was a great experiment, to see whether ham HF operation could be compatible with U-Verse's VDSL2 signalling.

VDSL2 delivers a bit stream over channels stretching from a low frequency to over 8 MHz, so it was a challenge to work at power levels over 50 W or so in the 160, 80, or 40 M bands.  We tried lots of things -- ferrites everywhere, shielding, etc.  At the same time, AT&T's technology improved, with higher bit rates and more tolerant modems.  We weren't too unhappy as U-Verse customers -- but that was only because I don't spend a lot of time on the air (especially QRO) during TV viewing hours.

Still, I have grown tired of having to think too much about my TV, Internet and phone service.  They should just work!  Even for radio amateurs.  Back to the cable world -- Comcast.

The problems with Comcast will undoubtedly come.  Maybe they'll throttle me if I don't watch enough NBC shows. But in 2 years, maybe we'll see Google or Verizon or somebody offering something more attractive?  Stand by.

KX3 IQ & Python SDR

It's a work in progress, but here's a shot of my Python / wxPython / Numpy "panadapter" display for the Electraft KX3.  The KX3 provides a very nice IQ output (wideband, quadrature audio), covering +/- 24 kHz around the VFO tuning frequency.

I have long been interested in building an SDR software backend using Python et al.   Two principles: (1) You don't understand it if you haven't coded it, and (2) Python is the quickest and often best way to put together complicated software.  It's most at home on Linux systems, but it is not hard to port most applications to Windows.  (Not quite so easy to port: hardware-oriented stuff like audio and Ethernet.)

Like most "friendly" apps, you find that 95% of the work goes into the display and user interface.  The numerical part is almost trivial, using Numpy:

    data = np.array(iqdata[::2] + iqdata[1::2]*1j)
    z = np.roll( fft.fft(data), SIZEC/2)  # place center freq in center
    pwrwork = pwrwork + np.square( np.absolute(z) )

The total code size is about 590 lines at this point.

This application (kx3iq.py) is really a remote control app.  I "beam" the IQ data from the KX3 via my Beagleboard XM and a UDP Ethernet stream to the Python app across the room, with Hamlib rigctld provide rig control.  Using 16 bit 48 kHz sampling, that's a data rate of ~200 kB/s without any compression -- doable over most ISP's these days, if you want a long distance remote.

#SteppIR down

It was the last straw.  Today, we had a "normal" Nor'easter storm, with NE winds gusting to ~25 mph, they said.  The antennas at AA6E had largely sailed through two hurricane / tropical storms and a few other major wind events.  But this "mild" one pushed us over the edge.  One of the reflector tubes popped off.  Fortunately, my policy of routinely retracting the SteppIR elements has paid off.  You can see a bit of the tape sticking out, but it looks OK from my vantage point at least.

This is where the tube fell, apparently without much damage in the front patio.  (The tree branch is from an earlier wind storm.)

Here is where things separated.  It looks like the rubber boot has separated, but the tube itself is probably OK.  The storm is still on, so I'm going to wait to do a more careful check.

The SteppIR is one of the original 3-element type.  It went up in 2004 IIRC, and has been trouble-free until now.  I'm not complaining.  We will probably have to bring it all down and replace the silicone rubber bits.

Best spam lately

Today's Spam

My candidate for most educational spam is above.  Checking with http://en.wikipedia.org/wiki/South_Asian_numbering_system and current exchange rates, I find I am being offered something like US $ 1.5M.

I won't bite.  They seemed to have missed their demographic. (Note to Centurylink!)

Cutting the cord: FB

My Facebook account is now "suspended".  It was a long time coming.  The many problems of being on Facebook are well known among internet-literate folk, but hard to explain to casual users.

As someone said, "if you can't figure out what the product is, the product is you."  FB makes money by advertising and by using tricky ways to get you to disclose lots of marketable facts about yourself.

The same facts can be used by almost anyone who wants to know something about you.  The most notorious case would be prospective employers, who are known to require you to give up your FB password, so they can see all your history.  No doubt the Federal government has similar interests in your politics or your research into exothermic chemical reactions.

We need to pull out of Facebook.  It's painful, because FB provides some very useful networking with people you want to connect with -- classmates, family, etc.  But it's not enough for me.

There are quite a few other social networking sites.  Yes, they're mostly free and they all share some of the same problems as FB, but that's where I am now.  Try me on Google+ (Martin Ewing) or on Twitter (@AA6E) or talk back to my blog.  I'm active on the ARRL member forum (AA6E), too.

You can suspend your FB account -- a kind of trial separation.  If it still seems wise in a week or two, you can have all your info deleted.