iiinova — where your digital self keeps evolving

Ted Dunning @bsky.tdunning.com · 30/09/2026

We have an idiot for a president.

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Ted Dunning @bsky.tdunning.com · 25/09/2026

Here's a hummingbird thinking. Big thoughts at the end of the day. #photography #birds @glengrambo.bsky.social

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Ted Dunning @bsky.tdunning.com · 16/09/2026

Here is the speed of the Julia one-liner implementation for various N. Note that the real problem is memory use through the explicit construction of the matrix. The computation itself is O(n^3) but memory usage is O(n^2) which becomes a serious problem. At n=50k, we need 10GB of memory.

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Ted Dunning @bsky.tdunning.com · 16/09/2026

Sure. My implementation in Julia (I don't even have R any more) is this pm(x) = median((x .+ x')/2)

The pseudomedian (see also here), also called the Hodges-Lehmann estimator, is less well known. It is affiliated with the Wilcoxon signed-rank test and can be computed by inverting that test, i.e., by finding the value that minimizes the signed rank statistic.. It is computed by taking all possible pairs of observations (including pairing an observation with itself), computing the midpoint of each pair, and computing the median of the midpoints.

From https://www.fharrell.com/post/aci/

A histogram showing the distribution of sample median, sample mean, and sample pseudomedian for 10,000 draws of 100 samples taken from a Γ(0.2, 1) distribution.

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Ted Dunning @bsky.tdunning.com · 15/09/2026

On the other hand, some days you really want the mean itself and not for central tendency. In the attached graph, 2/3 of the samples are to the left of 0.1 (the mean is garbage) but the actual mean of the distribution is 0.2 (the median is garbage) Horses for courses. Swings and roundabouts.

A graph of the results of taking 100 samples from the Γ(0.2, 1) distribution. 2/3 of the underlying samples are to the left of 0.1 which the median makes clear. On the other hand, the underlying mean actually is 0.2 and the mean is better at estimating this.

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Ted Dunning @bsky.tdunning.com · 13/09/2026

The t distribution is symmetrical. That isn't the problem. The problem is that for small degrees of freedom, it is very long-tailed. For dof=0.1, it can take a *very* large number of samples in a mean for the mean to be anywhere near normally distributed. Not many phenomena are that extreme.

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Ted Dunning @bsky.tdunning.com · 25/08/2026

It's on the edge of autumn and New Mexico is far away, but not so far that we can't get some Hatch chile. @ellen-friedman.bsky.social says these are hot. I didn't think so. #hatch #chile #nm

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Ted Dunning @bsky.tdunning.com · 21/08/2026

Moon, drowned in the sunset

A half Moon surrounded with a vivid sunset color around it

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Ted Dunning @bsky.tdunning.com · 29/07/2026

The nearby seismic waveforms are interesting regarding this video. The P wave arrives before the S wave and is orders of magnitude smaller. I think that cat is reacting to the P wave. The first P arrived about 7 seconds before the S wave and the cat jumped about 5 seconds before the big shaking

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Ted Dunning @bsky.tdunning.com · 18/07/2026

Monet is primarily viewed today as a prominent impressionist. What isn't so well known is that in his later years, he could be seen to be dabbling with surrealism.

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Ted Dunning @bsky.tdunning.com · 17/07/2026

London 1903? Or Chicago 2026? You decide

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Ted Dunning @bsky.tdunning.com · 11/07/2026

Really temperature. I've heard people in Phoenix complain about temperature this high.

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Ted Dunning @bsky.tdunning.com · 15/04/2026

Bank of America is trying to make sure their customers can't be part of class action lawsuits ... or much any lawsuits. Happily, consumers can still opt out of these one-sided changes. I have. My guess is that you should as well. #banking #consumers #consumerprotection #classaction

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Ted Dunning @bsky.tdunning.com · 29/03/2026

So the boards came back for this and the results were pretty cool. I wanted to make a filter to get high quality signals out of a cheap AD9851 board. Based on feedback from @de6u99er.bsky.social, though, I decided to add a two layer version. Here's an alt-text spoiler. 🧵 #electronics #hamradio

The theoretical and measured results for a low pass anti-aliasing filter for the AD9851 direct synthesis signal generator. The blue line shows the simulation with idealized components and has a small bump in response before it reaches 60dB of attenuation at about 120MHz. The green line (four layer implementation) and orange line (two layer implementation) show the measured performance. Each of the real implementations lack the small bump at the cutoff (probably due to finite Q of the inductors) but otherwise track the roll-off of the theoretical response very well. Above 120MHz, the orange line exhibits noticeably (~6dB) less attenuation than the theoretical or four layer implementation. The four layer implementation follows the simulation results very closely, however, all the way out to the limit of measured data at 290MHz.

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Ted Dunning @bsky.tdunning.com · 18/03/2026

The README describes the function. Here is a projected response with quasi realistic Q. The design methodology was to start with a designed filter with 65MHz cutoff, 0.2 dB ripple and 55dB stop band attenuation. Then I replaced components with what I had handy with simulation in KiCAD.

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Ted Dunning @bsky.tdunning.com · 17/03/2026

I just whipped up a design for a better quality anti-aliasing filter for chips like the AD9851. Most cheap boards that have the AD9851 have seriously bad filtering which leaves a very strong signal at the clock frequency (180MHz) and with any aliased signals. This filter should fix that.

A rendering of a small electronic component that implements a low pass filter for use with the AD9851.

See https://github.com/tdunning/low-pass

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Ted Dunning @bsky.tdunning.com · 03/03/2026

New "tool". I just have to get this little guy to let me work with it

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Ted Dunning @bsky.tdunning.com · 12/02/2026

All tuned up and ready to go.

The SMA scope probe assembled and connected to cables.

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Ted Dunning @bsky.tdunning.com · 11/02/2026

Building stuff is sooo much fun. It's almost more fun when it's tiny. Source is at github.com/tdunning/sma... #hamradio #electronics

A small circuit board designed to allow a scope probe to be built from SMA- terminated cable.

The circuit board has a QR code that links to https://github.com/tdunning/sma-scope-probe

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Ted Dunning @bsky.tdunning.com · 01/02/2026

Just to check that something in the world still works the same, I verified that you can still get into the tardis at Earl's Court station (on Google maps)

This is the blue police call box at Earl's Court station in London. It is one of the very few police call boxes left in England and is a site of pilgrimage for Doctor who fans

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Ted Dunning @bsky.tdunning.com · 31/01/2026

I have updated my toy project to make an SMA based oscilloscope probe based on building the first version. Links to the github, to a place you can buy the boards (for <$1 each!) and more below. #hamradio #electronics github.com/tdunning/sma... oshpark.com/shared_proje...

3D rendition of the attenuator to turn an ordinary RG-316 cable into an SMA based oscilloscope probe. This attenuator forms a voltage divider with the 1MΩ input of the oscilloscope with some capacitors included to maintain a flat frequency response.

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Ted Dunning @bsky.tdunning.com · 26/01/2026

It seems only right that somebody establish a B&B in New Mexico, NSW called Sydney, New South Wales. It would be right up there with the Indiana University of Pennsylvania, Indiana, Pennsylvania.

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Ted Dunning @bsky.tdunning.com · 26/01/2026

That complement is the rural place called "New Mexico" which is found in New South Wales (in Australia).

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Ted Dunning @bsky.tdunning.com · 26/01/2026

Today, from the annals of Great Marketing Blunders, I present the B&B near Acoma pueblo in New Mexico known as "Sydney, New South Wales". If this place actually exists, it would be completely impossible to find via a Google search. There is an interesting complement to this, however. 🧵

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Ted Dunning @bsky.tdunning.com · 10/01/2026

Looking good. Looking red. Smells sooo good.

A large pot full of posole cooking on the stove. The chili has been added and the color has turned very dark red

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Ted Dunning @bsky.tdunning.com · 10/01/2026

Posole at our house is a little bit late this year. But late is better than not.

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Ted Dunning @bsky.tdunning.com · 24/12/2025

I was putting on an ancient Tish hinojosa t-shirt this morning and got a good reminder. Yes, we can. We can cultivate awareness.

The back of a t-shirt that says in Spanish "si se puede cultivar conciencia". This can be read in two ways, we can cultivate awareness, or we can cultivate a conscience.

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Ted Dunning @bsky.tdunning.com · 24/12/2025

Here's a cool way to visualize how progressive lenses work. I printed a 2mm grid and taped it to the wall. Then I used an old fashioned clothes pin and cable ties to mount the glasses in front of the grid about 30-40cm away. Taking a picture focussed on the magnified part of the grid gives this.

A 2x2mm grid taken through a progressive focus prescription lens. The lens is about 30-40cm from the grid and the camera is about that far behind the lens focussed on the magnified portion of the grid.

This image clearly shows the unperturbed portion of the lens above the corrective region and transitional zones left and right of the zone with the highest magnification in the corrective zone itself.

The non-linear distortion of the grid shows why it takes time to accommodate this kind of lens. The amazing thing is that once you adjust, your brain compensates nearly transparently.

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Ted Dunning @bsky.tdunning.com · 14/12/2025

I just threw a quick donation at KiCAD. Those guys do some really wonderful work I get a ton of enjoyment out of playing with circuits.

A picture of a small printed circuit board designed using KiCAD

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Ted Dunning @bsky.tdunning.com · 06/12/2025

This has since been fixed on their web site, but it seems that the NYT now depends on readers for copyediting their headlines.

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Ted Dunning @bsky.tdunning.com · 19/11/2025

Leaves are beginning to fall in earnest in our neighborhood

A leaf which is turning yellow and red. It's suspended on the windshield
of a car with a neighborhood and other cars in the background out of focus.

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Ted Dunning @bsky.tdunning.com · 18/11/2025

Oh... and here it is with 6 nodes: Here's a reference to the algorithm in question. arxiv.org/abs/0803.3838

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Ted Dunning @bsky.tdunning.com · 18/11/2025

So I resurrected my old MetaEp code and in the process remembered a lot about the pathology of this kind of problem. Cutting to the chase, here is the result on an evolutionary algorithm solving with 20 nodes. You can see it lock into the gross pattern quickly, but then get hung up. 🧵

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Ted Dunning @bsky.tdunning.com · 13/11/2025

The idea here is that as the inductance increases, it passes more of the input drive and the op-amp converts that to a nice pulse. Simulating a component with a variable parameter makes this really easy! 4/🧵

The output from the circuit as a trace. It shows that the signal is low except when the slug is passing by at which time it goes to over 4 volts.

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Ted Dunning @bsky.tdunning.com · 13/11/2025

The cool (and simple) trick here is that the inductance of the coil is not specified with a constant value, but is given as {v(/slug)}. This says take the voltage of the labeled signal "slug" and use it as the inductance. I guesstimated this voltage based on how fast a slug will fall. 3/🧵

A plot of the voltage that controls the variable inductance. Most of the time, the value is quite low (2mV), but when a slug passes, it rises to a much higher value (10mV) consistent with an increase of permeability by a factor of 500. For a short time, the value is constant as the slug is entirely in the coil and then it declines back to the lower value.

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Ted Dunning @bsky.tdunning.com · 13/11/2025

Ooh ... fun. A friend is playing around trying to detect an iron slug falling through a coil. To help with this worthy effort, I suggested some simple circuit designs and found out a) KiCAD has ngSpice built in and b) you can have variable inductances in a circuit! #kicad #electronics 1/🧵

A circuit diagram showing an 80kHz pulse generator driving a 100 ohm resistor and a variable inductor. The voltage across the inductor is amplified and rectified by an op-amp circuit. At the bottom left is a pulse generate that generates a wave-form that drives the value of the inductance in the coil over time. That wave-form represents two slugs being dropped through the coil.

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Ted Dunning @bsky.tdunning.com · 12/11/2025

Looks like our Canadian friends are going to get quite a show tonight with the Aurora. www.swpc.noaa.gov/products/aur...

A map showing very high likelihood of Aurora being visible over most of Canada, much of Green and nearly all of Alaska. Only the northern tier of continental US states have a moderate or high likelihood.

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Ted Dunning @bsky.tdunning.com · 09/11/2025

Something strange happening with hertz. Pick any car in the gold zone, they said. Difficult choice it turns out. The white car in the distance isn't in the zone, btw. Also nobody in the office in the parking lot. I've never seen this before.

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Ted Dunning @bsky.tdunning.com · 03/11/2025

There's still time. If you haven't done it already, go vote!

Sticker that says I voted in many languages

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Ted Dunning @bsky.tdunning.com · 18/10/2025

Demonstrators in Palo Alto? Get distracted a bit!

Demonstrators lining up to get ice cream from an ice cream truck

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Ted Dunning @bsky.tdunning.com · 18/10/2025

It turns out that a huge number of people stayed in the park and never marched

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Ted Dunning @bsky.tdunning.com · 18/10/2025

Holy s*** this is bigger than before. San Jose has turned out in force!

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