roamingryan

I have never understood how this was effective against a determined adversary. An arbitrary limit like 100ml is pointless when there is no limit to the number of times you can pass through the checkpoint.

I was left wondering the same.

My best guess would be that slope detection could be converting the FM signal into AM. This happens in circuits where the response is strongly dependent on frequency (see [1]). A specifically designed filter is typically used, but a resonant circuit like the headphone wires could do something similar. But then you still need to get from AM to audible, and to do that you still need some sort of non-linearity in the system. Some possibility non-linearies could be a poor connection resulting in a whisker-style rectifier junction, or perhaps a magnetic permeability non-linearity in the headphone speakers. I'm sure there are others.

Related, but probably not relevant: Stereo FM broadcast signals in most parts (all parts?) of the world also contain an AM subcarrier. The primary FM carrier has the L+R audio content and is used by both monaural and stereo receivers. Stereo receivers make use of an additional AM modulated sub-carrier (+/- 38 kHz from primary carrier) to obtain L-R audio content. I don't believe this AM carrier is directly rectifiable because it does not manifest as envelope modulation in the full signal.

[1] https://www.electronics-notes.com/articles/radio/modulation/...

I've been down to McMurdo for a research trip. A couple of things that outsiders find surprising is that most of the people there are support staff and only a small fraction (maybe 20% or so) are the scientists. The support staff are basically people from all walks of life... fireman, carpenters, cooks, mechanics, etc. Basically everyone you need to make a modern city run. However, because of the selection processes, those folks are almost all extremely talented and at the top of their specialties. The number of "swiss army knife" individuals I met with very broad skill sets was astounding. The challenges associated with living and working down there tend to draw quirky and motivated individuals like bugs to a light. And many return year after year. It's a wonderful community.

I second this. I picked up one second hand a while back. The placard indicates it was built in 1997. It needed a good cleaning and had clearly seen a lot of use, but is perfectly functional. The shower arm was showing slight signs of rust around the hole but getting replacement parts is trivial as the design hasn't changed in decades.

Seems to work OK for me. I will point out that it is very "coarse" and only has 4 possible settings. Perhaps not the best choice for a slider, but perhaps they made that UI choice just to match the other sliders?

Very nice project. Much better than dealing with the raw tables/curves from Fair-Rite which seem to have been photocopied again and again over the ages.

Really nice of them to release this. However, unless I'm missing something, the HDL for the FPGA on the Time Card is not part of the release. It looks like it uses a proprietary IP core from NetTimeLogic

https://github.com/opencomputeproject/Time-Appliance-Project...

They do include FPGA bit streams, but it's disingenuous to claim a fully open source release.

I built out a simple "technology access" solution for my late grandma about five years ago. It was just some simple scripts running on a raspberry pi. The scripts would fetch emails from a gmail account, extract the attachments, and display them on loop. The subject line of the email, sender and the date were overlayed on the image.

The advantage over those IoT picture frame products was that I could use any display I wanted. A cheap 32" TV was perfect. This was key as her vision degraded. The approach also allowed anyone in the family with email to send her photos, no proprietary apps or accounts required.

She passed away mid-Covid and I didn't get to see her in her final 6 months, but she always bragged of her "picture machine." I think she was the envy of many of her fellow nursing home residents!

Many modern FPGAs now include dedicated logic for config SRAM "scrubbing." This logic continuously checks config frame checksums to identify upsets. These can then be fixed in real-time either using the error correction properties of the checksum technique, or from the non-volatile config memory (typically NOR flash). It's also important to note that only a subset of the SRAM config bits are critical for a given application. Usually this is a small percentage of the overall array.

https://www.xilinx.com/support/documentation/application_not...

If even higher levels of reliability are needed, there are rad-hard-by-design FPGA families (e.g. Xilinx Virtex 5QV). These have a special config SRAM cell that has more charge storage sites than a conventional SRAM cell. It is less area efficient than a conventional SRAM cell, but geometry of the charge storage sites ensures that a single cosmic ray can't flip the state of a majority of them. Essentially the cell can self-correct, no scrubbing required.

If I had to list one thing it would be this:

People everywhere, regardless of their race, religion, politics, or wealth are generally decent and primarily interested in making a better living for themselves and their family.

Some may see this as an obvious fact about human nature. However, for someone like me who grew up viewing the world through the lens of the US media, I used to think otherwise. Travel fundamentally changed my views in this regard.

I left my job when I was in my late 20's to make a year-long round-the-world trip. Leading up to it, I was up for a promotion at work and my managers and colleagues were very skeptical about my decision to leave at such a time. I'm so glad I stuck my guns. It was easily one of the best decisions I ever made.

My partner, who I had recently started dating at the time, was unhappy with her job and also decided to take the leap. In 2011, we spent 313 days traveling around the world together. Ten years later, we're still together!

As for trip logistics, very little was planned in advance. We both gave up our apartments and put our belongings in storage with friends and family. We started the trip with one-way tickets from the USA to Asuncion, Paraguay. Not a common first destination on a RTW trip, but we had used miles and the cost was the same price to go to a relatively obscure place rather than a more common one. Paraguay is a fun one if you are vegan/vegetarian, but that's another story.

Prior to the trip I had stockpiled a decent amount of frequent flyer miles. The late 2000's were crazy with respect to mile program promotions, but that's a whole different story! Those miles helped offset most of the long-haul travel costs but on the ground we preferred to travel as cheaply as possible with buses, trains, etc. The main thing the miles enabled was access more remote and uncommon destinations. As an example, one of our travel days took us from Mongolia to Palau. I don't think that's a common origin-destination pair.

I will second what others have posted here about moving slow. The places we have the fondest memories of are the ones where we spent the most time. This cuts both ways though. When you are traveling/living this lifestyle it can take some effort to find that magical mix of affordable housing, good food, and interesting activities. When all those factors align, it's easy to "get stuck" and then later have to cut things from the larger itinerary. Burn out from being on the road is another real factor. We felt it strongly at about the 6 month mark, which, conveniently was timing with a detour back home for my brother's wedding. After that we were eager to get back on the road.

Regarding costs, we found the trip to be quite affordable. Our burn rate over the year averaged out to 1000 USD per month per person, however, we had intentionally avoided the more expensive parts of the world (e.g., Europe, OZ/NZ, etc.). Aside from a few splurges, we chose to stay in budget hotels/guesthouses wherever possible. We had also offset much of our long-haul travel costs with airline points/miles.

I would love to take a trip like this again and I'm glad I didn't save this experience for retirement. I can't speak highly enough of doing something like this if you have the means.

If anyone is interested in more details about the trip, I kept a blog here:

http://www.roamingryan.com/

Most of the major component distributors: https://www.findchips.com/search/Adalm-pluto

Plane or inclination changes are expensive. Phase changes are cheap, relatively speaking.

Not necessarily. Watermarking an audio stream like this wouldn't require that high of a bit rate. It could easily be hidden "under" the content using coding techniques like direct-sequence spread spectrum.

A real world example is GPS, which uses a spreading code to provide about 30 dB of gain. GPS signals aren't directly observable relative to the noise floor in many receivers. It's not until after the signal is "de-spread" that it becomes observable in a spectrogram. This process requires prior knowledge of the signal structure.

In short, if you don't need to send data at high rate there are many ways to hide your signal.

Interesting because HughesNet as it exists today is serviced with GEO satellites. These can't hit the latency requirements of the RDOF program

Only the OneWeb sats at LEO can deliver on the latency requirements.

It will be interesting to see what happens as the FCC reviews the "long form" applications.

Does anyone know why Hughes, a OneWeb investor, placed and won bids solely within the state of Rhode Island? Is this some sort of squatting play to qualify them for future solicitations?

Given the state of OneWeb, it seems very unlikely they will be able to deliver even across such a tiny geographic area.

Yes. Guided munitions. Some artillery shells incorporate guidance electronics that survive these sort of conditions.

It is also worth noting that propagation velocity in glass fiber is about 60% slower than free space. Once the constellation is dense enough and OISLs are working, they'll be able to undercut fiber latency. That is, if they actually decide to route signals in a purely latency-optimized manner. I wouldn't be at all surprised to see some sort of tiered pricing related to latency and latency jitter.

No doubt the scummy high frequency traders are already jockeying to get out in front of this change in the telecom industry.

I'd be surprised if that is the outcome. MIT facilities tends to be quite tolerant of stuff like this.

That is correct. US Citizenship is not a requirement, however, I believe you do need to have a US mailing address.

The MIT Radio Society (W1MX) has gotten their online process up and running and is regularly scheduling sessions.

http://w1mx.mit.edu/ham-exams/

PCLATH stands for Program Counter LATch High (byte).

In this case latch refers to the digital design technique where you have a register that holds bit(s) until some other event happens. The event in this case is a write to PCL. Once the event occurs, PCLATH is transferred to PCH synchronously/atomically with the write to PCL.

Not quite what you are describing, but Universal Radio Hacker is a useful tool for reverse engineering protocols.

https://github.com/jopohl/urh

Similar story here. I didn't completely tank my GPA due to solar racing (Rose-Hulman, ASC2001) but it certainly didn't do it any favors. None of that mattered though as the practical engineering skills I gained far outshined anything academic on my resume.

Thanks for this alternative.

One suggested edit: Savor should be Sabre

That's not really the point. The course is designed to pair you up with the equipment/resources and have you actually make stuff. The learning comes from applying the knowledge, not just acquiring it.

Much of the remaining latency is likely coming from FEC and interleaving needed for the RF links.

http://en.wikipedia.org/wiki/Forward_error_correction#Interl...

FEC and interleaving induced latency will likely become the dominant term for LEOs.

You should check out mosh for use on high latency connections:

https://mosh.mit.edu/

LaTeX got a good workout compiling that tome!