Sunday, August 13, 2017

AM Broadcast Band, day vs. night

This is a comparison of the broadcast band during the day (at top) vs at night (bottom). Many stations are required to lower their power and/or change their antenna directionality at night because the absorptive D region of the ionosphere disappears and allow lower frequency waves to propagate via a skywave. Some stations, called clear channels, are allowed to maintain their high power at night. Chicago happens to have quite a number of them-- you can see them at 670, 720, 780, 890 and 1000kHz. Local stations including the clear-channels are marked (minus 1690). At night, you can see a carrier at nearly every 10kHz, showing many of the AM stations listenable at night from across the US. WSCR 670 and WBBM 780 are unfortunately also using HD Radio. Local switching power supply noise appears as very impulsive (fast horizontal bands) at about 615, 925, 975, 1090, 1230, 1500, 1550 and 1850kHz. The fundamental for some of these appears to be at 306Khz. You can see in the IF this signal, as well as the much weaker DGPS signal at 304kHz from Mequon,WI. This was taken with a simple indoor dipole of 42ft length (with some turns in it) and a v 1.3 dongle with HF direct sampling (Q-branch) and AGC turned on.

Thursday, August 10, 2017

The radio satellite CUTE

The nanosat CUTE, or rather the CUTE-1.7 + APD II, sends out a beacon in morse code. I picked it up with a simple antenna and a SDR. Time increases to the right in the image and frequency is the vertical axis. It shifts because the satellite was moving away from me during the capture. Track CUTE for your location.

Monday, May 02, 2016

SAR image of the Calumet region of Chicago

I've been working on manipulating the large images offered by the Sentinel satellite. I found an image of the city of Chicago region on April 10th, 2016, and have been taking a look at it. The data image is 25000x16000. I grabbed the HH(the Horizontal transmitted, horizontal received polarization) and HV images (horizontally transmitted, returned vertical polarization), normalized them and made them R and B in an RGB set. The G I created by adding the two images together. Adjusting the hue allows for greater visual impact of the image. This is the Calumet region of southeast Chicago and Northwest Indiana, a heavily industrialized region. Lake Calumet, Lake Michigan, Wolf Lake, and the Calumet River/Cal Sag all show with no reflectivity at this normalization (you'll recall the previous post where Lake Geneva had some return from waves). The ArcelorMittal steelworks sits out on the right as a highly reflective region of pipes, stacks, rail cars and other industrialness, with the BP Whiting refinery to the left of it as another nearly continuous return. Long linear blue streaks are presumed oil or ethanol conveys consisting of mile-long packs of tanker cars that are bright in the HV channel. Shipping containers, barges, oil tanks and rail cars that are not tankers all reflect highly in the HH return. Even Binions Horseshoe floating casino shows up brightly. A bright return in the upper left I assume is the tower at Promet steel. blue-cyan-calumet

Wednesday, April 27, 2016

Synthetic Aperture Radar data of Lake Geneva, Wisconsin

I happened upon a nice description of how to grab data off of the ESA's Sentinel satellite via Evan Appelgate and there's a bunch of interesting things in the data. It was taken just this Tuesday morning at 7:11AM. The winds were out of the north at 8MPH and overcast. You can see in the image the effect of the wind creating a rougher, more radar scattering surface on Lake Geneva--dark at the north shore, transitioning to a very slightly rougher surface to the south.

Click to enlarge. There's a lot more interesting things to look at--that's just the first thing that jumped out at me.

Sunday, March 06, 2016

A really bad soldering iron

I picked this soldering iron out of the ewaste recycling stream that students dump at the end of the year, figuring I could use another iron. I knew it ran hot. Yesterday I was attempting to create a data cable between a PC and a radio and was annoyed at how quickly oxidized the tip had gotten. After cleaning it and trying again (failing ultimately because the PS/2 keyboard connector happens to not use one of the pins) I noticed a subtle warm color to it--and thinking it was just the orange light pollution reflecting off of it, but then I put two and two together and realized it was black body radiation. And that means this soldering iron is really really bad.
The camera appears to have a fairly good IR block filter on it, so the colors match better to the eye's response. On a weaker camera I would expect a purple appearance to it as the blue Bayer filter will pass IR circa 900nm.

Thursday, February 11, 2016

long term survelliance flights over Chicago

Perhaps you've heard of constantly circling Cessna planes, spending hours circling high above US cities. Today I happened to see many of them over Chicago. Looking at FlightRadar24's live feed I saw two. Their data is much more complete than my limited ADS-B receiving capability. The first was a Cessna, high at 9,000ft. It looks like it came from DuPage County airport, and has done a number of similar flights in the past few days. I was able to spot it in binoculars, and in doing so also picked up an identical looking plane holding an identical path, but not on ADS-B. I presume I was seeing a shift change, but one never knows. It had the 4414 squawk, and matched the false front company 'OBR Leasing'. Not only Cessnas, but a Bell 407 helicopter was hanging around too at a lower altitude further west, closer to Midway.

Wednesday, June 24, 2015

Morse code over laser light with an Arduino

19. After another of my famously lavish parties, I sometimes walk alone out to Promontory Point at exactly 10:00 p.m. Thursday and glance lakeward, out at a blinking light on some distant shore, and think of Daisy Buchanan. That light winks on and off, unattainable, a powerful metaphor for|wait, is that Morse code? [5 points for lights over a mile away; 15 points for lights over 5 miles away; 0 points for lights that are only metaphors] For this Scav Hunt item I used an Arduino to turn a laser pointer on and off in morse code:
#define pulseHigh(pin) {digitalWrite(pin, HIGH); digitalWrite(pin, LOW); }
#define RESET 13  // Pin 13 

void setup() {
pinMode(13, OUTPUT);

void loop() {
      delay (3000); 
      delay (1500);
      pulseHigh(RESET); // off

void dot()

void dash()

void space()

I checked and saw at that the path from Adler Planetarium to the Point was just a touch over five miles and free. I could identify the Point fairly well in binoculars; I aimed the laser pointer by fixing to a tripod, testing the aiming by hitting nearer objects (a beach buoy nearby happened to be retroreflective which helped quite a bit) and then carefully moving the system towards the Point. I turned it off whenever boats went near the beam. To prove it was me, the judge requested I manually hit the key a few times--since I had only a programmed 'SCAV' (yes, it says GASH above), I manually connected the pointer to 5V & ground on the Arduino. It was powered via a 12V battery and a cigarette lighter USB charger to provide 5.1V.

Friday, June 20, 2014

insect on clematis

insect on clematis insect on clematis A cute colorful insect hanging on out a clematis vine. Graphocephala coccinea, red-and-blue leafhopper.

Monday, March 17, 2014

Hyde Park Hum

Background: Hyde Park Residents Puzzled by Mysterious Noises, Vibrations, Loud Hum at Night.

Some random thoughts:

I hear a vague distant sound sometimes, like a locomotive engine that never leaves. It came up earlier in the year, but beyond suggesting it sounded like it was coming from the SE from my location, didn't do anything else. Recently it came up again, and evidently for some people, is intolerable. These people live east of the Metra Electric tracks in various high-rises and other multistory buildings between 51st and 56th St (specifically, people in the Windemere, 1700 E. 56th, 5490 South Shore, 5479 S. Hyde Park, and 51st and East End have mentioned it). People on the west side of 1700 E. 56th higher up (like 28th floor and above) seem to have it the worst--and they claim their management have turned off every system in their building to prove it wasn't local to them. I originally thought it was related to the opening of Earl Shapiro Hall on Stony Island, to the SE of me.

I went wandering around a few weekends ago on a slightly breezy and roughly about freezing 0C evening with an ipad running a tuner app that offered a fairly nice spectrum analyzer and I could see a prominent tone at about 85Hz that came and went, and varied in intensity. It turned on and off with a period of several minutes. I saw it best in quiet places. I saw it underneath the Metra tracks at 57th. I did not see it get any louder when I pressed the tablet against the UC maintenance building on Stony Island between 56th and 57th. I saw it at 54th and Cornell. I did not see it at 53rd and South Shore. I saw it in the alley between Everett and Hyde Park Blvd between 53rd and 55th. I see it in front of the home at 5522 S Hyde Park Blvd. I see it quite strongly in the alley between Cornell and Hyde Park Blvd between 55th and 56th, strongest at the back of 5528 S Hyde Park Blvd. It is quite strong there and next door at 5540 S Hyde Park Blvd, the Poinsettia Apts and Broadview Hall, respectively. Given that, I wondered if my aural direction of SE is real, or some reflection from Vista Homes.

The iPad software is limited to being sensitive to approximately 40Hz and higher, with a realistic limit of about 60Hz.

Things it is not: It is not related to the power grid, which mostly produces noise at 120Hz, with 60Hz appearing occasionally, plus all harmonics. I am very familiar with that noise. It is not a moving train. When a freight train goes by, the locomotive produces several harmonics in the sound area while it passes, but they have a Doppler component. The freight component offers deep rumbling at 9 to 11Hz. Metra trains produce lots of frequencies between 100-200Hz.

I have a PC laptop at home with a microphone running Spectrum Laboratory and Spectran, which I can vary the FFT size, sampling rate, and other variables which allow me to get much lower in frequency. The practical limit is 10Hz which seems to be the microphone's limit. That software is not calibrated, and I suspect it is off by 10Hz, since I see a discrepancy between the iPad, the PC, and what I expect to see.

I have seen it at home in the early evening, evening, at night, in the morning. I have not been at home during the day very much, but I suspect it is there then as well.

I embed an image of the monitoring software taken last night, 3/16/2014, between 10:30PM and 11PM below. Time is horizontal, frequency goes up vertical. Anything that is strongly vertical is likely me moving around, very local, moving the laptop, etc. Like at 22:37 I think I moved from my midlevel upstairs. You can see the "110Hz" horizontal line, which if my PC is off by 10Hz, could be the ubiquitous 120Hz AC hum omnipresent.

The thing I call the 85Hz noise you can see is recorded here between 70 and 80Hz. And it has some variance in frequency, always in the same pattern, always changing in a discrete manner. Another fairly signifcant tone is visible starting at about 22:31, in between 30 and 40Hz. It gets quieter when I go upstairs at 22:37. You see it changes discretely as well, but in a different way, than the "85Hz" tone. A discrete change like this is usually the sign of a controlled system.

The wispy, broadband thing at 22:52? I believe that was a jet plane. I don't recall that specific one, but that's what they look like.

A garbage truck going down the street looks like this: . The horizontal ticks are one minute apart here and with a different sampling rate and such the 120Hz appears to show up at 120Hz.

There's more on the flickr stream, if you take a look. I think this one is earlier yesterday evening and you can see more of the discrete hum changes, plus non-discrete changes, etc. It's hard to pin down.

I also was running spectran on some screenshots, showing lower frequency noises. You can see prominent tones at 46-47Hz and 29Hz: .

One question I do have is wondering if everyone is complaining or hearing the same sound. The different aspects of the "85Hz" tone vs the stuff at 30-40Hz is suggestive of two different systems, and yet they are both prominent. One could be the window rattler and the other could be the one you actually "hear". This is all speculation on my part. There's a lot of further investigating (and speculating!) to be done here, but it will take time. In an ideal world one would be able to visit the facilities of various buildings to see if the systems are there or not. Or have more time to measure the intensity in a number of places to get a better map. I thought I had found the source at 5528 because there is a metal chimney pipe the length of the building that seemed to be at the loudest area. In retrospect, there is a large pipe at Broadview in the rough area of the loudest ground signal, but it's elevated and away from easy access.

What is the source? Is it some fundamental of a system motor, it is a resonance of a exhaust pipe? Why does it change?

Atmospheric effects can bend sound down and return loud noises from the ground back to distant areas because the sound is gently bent from the change in the speed of sound with temperature. Are we hearing something more distant like a train switching station from somewhere else?

More speculation: I would bet the noises go away once it warms up.

Anyways, more to look at, more to explore.

Wednesday, September 18, 2013

random recent interesting titles

Oversharing: Yesterday's catalog search items that caught my eye. (My search was all T acquired in the past six months published in the past four years in English)

The future of post-human waste : towards a new theory of uselessness and usefulness / by Peter Baofu.

Masters of light : conversations with contemporary cinematographers / Dennis Schaefer and Larry Salvato ; with a new preface by the authors ; new foreword by John Bailey.

Chemistry of fossil fuels and biofuels / Harold Schobert.

Lightwave engineering / Yasuo Kokubun.

The diner's dictionary : word origins of food & drink / John Ayto.

Indigo : the colour that changed the world / Catherine Legrand.

The science of nutrition / Janice L. Thompson, Melinda M. Manore, Linda A. Vaughan.

The disappearance of darkness : photography at the end of the analog era / Robert Burley.

Thursday, June 27, 2013

lemon juice and fine steel wool works on rust on a stainless steel dishwasher

I had a rust stain on the interior of a stainless steel dishwasher from contact with a rusting pan, and after having no success with CLR and just a paper towel, I applied some lemon juice, let it sit a few minutes, and then gently rubbed with #0000 fine steel wool, and the stain was removed. I suspect the magic was the steel wool. I did test it in an inconspicuous space to make sure I wasn't going to scratch up the surface. I noted that GE approved citric acid for stainless steel dishwashers beforehand.

Wednesday, February 13, 2013

Why toolboxes and tool handles stink.

Tools with Cellulose Acetate Butyrate handles

For years I've encountered this issue, and it always perplexed me: why do a lot of toolboxes stink? I had always assumed it was related to heavy use with sweat and dirt and zero cleaning, but after I started encountering it on my own, barely used tools, I started looking into it. You can find some posts on DIY forums asking the same question, and how they could never clean the toolbox well enough to get rid of the stink.

Eventually I found someone who pointed out it was coming from the tool handles, and then they pointed out the culprit: tool handles made of Cellulose Acetate Butyrate. A thermoplastic, it offers excellent UV and solvent resistance that cellulose acetate doesn't offer. And it feels in the hand like a natural substance, something that is almost intangible, like a tool that is made by craftsmen, a characteristic that a polyethylene or polypropylene handle does not have. CAB also offers no splinters like the older wood handles. It also can be very clear. And when that plastic begins to degrade, it releases free acetic acid and butyric acid.

The odor of vinegar is a familiar sign to those in the film and photographic business; the cellulose acetate backing of film releases it as it degrades. I once visited a famous photographer's house and his office where he stored his negatives had that acrid odor--while for a photographer it reminds you of the darkroom, the midpoint of the creative process, it also brings to you vividly the end of the process--the decay of the work.

The butyric acid, one of the carboxylic acids, with a formula of CH3CH2CH2COOH, just smells like, in polite company like parmesan cheese, or like rancid butter or vomit. It's not nice above a certain concentration. Once I discovered this I immediately spent a little time sniffing each tool I had, and in short order discovered the ones that are the problem. They immediately got isolated from the rest, because the free butyric acid really does migrate and make everything unpleasant. I thought about giving the tools away, but really, who wants such a tool, even if free? I was going to throw them out, but that made me feel bad. And I think I've found a solution to stinky tools. I carefully fully coated the handles in two coats of shellac, a natural sealer, and now they don't smell to my nose.

Monday, January 21, 2013

CFL lifetime report #2

A third CFL failed in my torchiere conversion I did back in the winter of 2008. I used this light about 7 hours a day consistently until mid 2011, then for about 4 hours daily since then, which gave a lifetime of this compact fluorescent bulb from n:vision of about 11000 hours. I'm starting to evaluate and switch to LED bulbs as circumstances warrant--I went out and bought the Philips L-prize winning 10W EnduraLED bulb as a birthday present for myself. Whether to get more is a good question given its cost of $40 (it currently is cheaper to buy them at a big box store like Home Depot than online). I really do like the 92 CRI; the question is it that sufficient enough reason to buy it versus the previous generation of 80 CRI AmbientLED? The cost of electricity isn't a reason: 10W for the Endura versus 12.5W for the Ambient means a couple of dollars a year if left on 24/7. The lumen ouput might be--only 800 for the AmbientLED versus a bountiful 930 lumens for the EnduraLED. If I went by cost only for 80-ish CRI the CFLs still win for the short-term. But I am tempted by color accuracy, which is somewhat important for me, at least in food prep and photography viewing. None of this moves into the realm of other home lighting, which I'm running into the questions of dimmers, recessed cans, appliance bulbs, and the aesthetics of bathroom fixtures. And not to mention essentially lighting doesn't really cost that much for me annually, compared to other costs.

Thursday, April 26, 2012

Improvements on my first cigar box guitar build.

To improve my first cigar box guitar build, I added a piece of 2" x 1/4" mahogany mull casing (ripped to 1.5") to the neck. I sanded it multiple times and applied multiple layers of clear shellac to it. I glued it to the neck with wood glue (while clamping I ran into issues with ink bleed on my clamp softeners). Then I also added fret marks with a silver sharpie (which then smeared while trying to clean things). I also screwed the neck to the cigar box in two places hoping to eliminate some odd buzzing/high harmonics that were occuring. Some of them were coming from the nut and/or bridge because the strings were not fully engaged or trapped by a notch in the nut or bridge.
fretless cigar box guitar
For the nut and the bridge I used bamboo chopsticks, harder then the native wood used for the cigar box. mahogany fret board
neck and nut