madengr

Nice report. I wish beamformer ICs were made for lower frequencies, but everything is targeting X-band and higher.

I’m using 4x A6000 Ada cards for EM simulation. They have 48 GB ECC and 2-slot width so can be accommodated in a server case, versus 24 GB non ECC and 3-slot width for the 4090. They are actually faster for FP32 than the A100, but really poor for FP64.

Watch there now be a cassette renaissance like there was a record renaissance, despite the cassette having horrible audio quality compared to a CD.

Most antennas actually have a large radar cross section (RCS), with simple dipoles being some of the worst. An infinitely thin dipole (a current filament) has a non zero RCS even though it has no physical cross section.

In theory, a reflector antenna can have a zero RCS, so putting a reflector behind a dipole will reduce the RCS. It’s totally non-intuitive.

Don’t buy the damned things. I just bought a 1989 Toyota pickup. Manual transmission, locks, windows, etc. Super reliable and easy to work on. It’s got a standard double-DIN stereo opening, so you could install the latest touch-screen gizmo if desired.

Expanded polystyrene has an extremely low loss tangent and dielectric constant, so I fail to see how microwave heating causes more chemical leaching than hot water.

The 1973 movie Genesis II also had travel tubes on a post-apocalyptic earth.

For my 5th Xmas I still remember getting a giant Eagle ship. The cockpit was removable from the center structure and the pilots could eject.

I wrote this years ago with that intent, though I don’t know you’d get audio back in real-time.

https://github.com/madengr/ham2mon

I have one too, on an active magnetic loop, which does a decent job of nulling near field interference.

http://kiwisdr.lounix.net:8073/

Not only that, but being able to play Doom (or maybe it was Wolfenstein) while downloading at 14.4k was amazing. I believe I used PMComm and of course a 16550 serial card.

I used it extensively in college in early 90’s, as Windows 3.1 seemed so primitive, but then a couple of years later Linux kind of took everything by storm.

I’d expect nonetheless from NY, where they trample on constitutionally guaranteed rights as much as possible.

Maybe they should require all STL and Gcode to be submitted to the state for review.

Yes, there are companies specializing in this:

https://www.deepsig.ai/

You know how Nyquist says you must sample at minimum twice your highest "frequency" or your get aliasing in your spectrum? It's the same with antennas except you must sample at least 1/2 your wavelength or you get grating lobes (the equivalent of aliasing) in you far field pattern; it's all the same math. A sample in time is equivalent to an antenna element sampling space. A big reflector is equivalent to sampling everything at once with no gaps; it's bandwidth independent. You can only put array element so close together, limited by the size of the element (itself is limited to a fraction of the lowest wavelength), electronics, and unwanted inter-element coupling (though there are tricks to take advantage of this coupling and make very wideband arrays).

If you leave "gaps" in your array elements, that's not a problem receiving strong, periodic signals. You can physically move the elements to fill in the gaps to remove those lobes; the equivalent of an equivalent time oscilloscope or a synthetic aperture radar. The problem is you can't do that when transmitting since you only have one opportunity to send something (non-periodic).

There are other disadvantages with phased arrays. Each amplifier has to be matched in amplitude and phase. I've had to bin lots of amplifiers as some have phase compression and some phase expansion over amplitude. That distorts the pattern over the pulse.

On the receive side, each receiver has thermal noise un-correlated with the others. So for N antenna elements, you received signal-to-noise scale proportional to sqrt(N) instead of N like you have on transmit, or with a big reflector. This is why arrays suck for very weak signals. Notice NASA keeps building big dishes for their DSN instead of "cheaper" arrays.

Then there's the whole timing and phase noise issue with distributing an oscillator.

Tough you can only make a reflector with about 100 dB gain.

It had a powerful transmitter for radar work, and there are advantages to having a single, giant aperture when it comes to maintaining low sidelobes, power amplifier coherency, etc.

Comprehensive part libraries are not an issue. It just needs a basic set of symbols. Most people doing PCB design will create their own symbols and footprints. Altium has an excellent footprint generate, which you can then tweak the output.

Saving is futile with a 3% loss on your money each year. Unless you invest it you are losing it.

I was doing some orientation sensing 20 years ago with an IMU and ran into the same problem. I had never known at the time it was gimbal lock (which I had heard of) but did read quaternions were the way to fix it. Pesky problem.

“Now you can tell time and measure current on the go.”

So it comes with current probe built into the band?

Look up Engineering Explorer Post for high schools students. Each month the attend a presentation on an engineering discipline, and the a site tour. My kid got to visit a nuclear reactor, food packaging manufacturer, biomedical device development, aircraft maintenance depot, etc.

This is mine. Select the timecode decoder:

http://kiwisdr.lounix.net:8073/

My wife was a process engineer in microelectronics. She is now doing data engineering and ML, and doubled her salary. She will never return to that industry.

Possibly, but the OP is probably measuring the equivalent of back-to-back series diodes, which would be very symmetrical (if built on the same process). With soldering though, I’m sure they are not equivalent. As the other poster said, they need Ohmic contacts.

You sure it isn’t Schottky diodes formed by the metallic contacts that are interfering with the measurement of the bulk germanium properties?

I’d sputter deposit metallic contact regions and solder to those, then maybe compare two different thickness samples and look at the difference in resistivity vs. temperature, essentially de-embedding your fixture.

> but had very little in common with the book series

Which was why it was crap. I couldn't watch pat the first episode.

The most popular city, according to Zillow, is Prairie Village, KS.

https://www.zillow.com/research/most-popular-city-2022-31925...

This is about 1 mile from where I live in Overland Park, KS. PV is all single family homes with near zero apartments. Of course the city is trying to re-zone to put in higher density housing, and the population is vehemently opposed to it; I don't blame them. People move there for that reason. Higher density leads to more crime and other frustrations. People learned their lesson from the pandemic.

Crimping on cars is probably just to save money, and some of the wire they use is garbage. Solder is pretty soft, especially lead based. Silver solders are more brittle and we don't use them for high reliability applications. Gold also has to be removed as it will embrittle the joint. For wires soldered to a PCB you can stake the wires with an electronics grade RTV, then bundle with twine, staked with epoxy. I have used low-outgassing RTV for space applications that costs $600 a tube.

A sharp punch (like a center punch prior to drilling). It is pushed in with a certain force and the mask mesh can only spread so much; there is a groove on the neck of the punch that defines the depth limit. You do this on a few areas of the mask then date the side of the mask to indicate it was tested.

A guy in the next strip had his mask puncture and the blade (saber) went into his mouth, and punctured through his pallet into his sinus. Could have been a lot worse.

This guy never let his mask dry, storing it in his bag, thus even the stainless will corrode. Thus mask testing every tournament.

LOL I had one of these. They made them with both red and green LED for the eyes. I only got a Big Trak when I was 40 and they re-released it.

Nice restoration. I have a Hallicrafters SX-62 I need to finish restoring. It cool to see Soviet Union printed on the glass.