Chasing RFI Waves – Part Seven | Hacker News Reader

Chasing RFI Waves – Part Seven

raoulpop.com

300 pointswalrus01118 comments

This was one of the most wicked cool things I've read in a long time.

I grew up in a TV market that was UHF only (South Bend, IN) in the 1970s. TVs from before about 1963(?) didn't have to have UHF dials. So a company named Blonder-Tongue (Blonder was pronounced like blunder) produced UHF receivers you could attach to your TV through the little screw tab things on the back, the predecessor to the coax input. I had never seen Blonder-Tongue referenced anywhere except in nostalgia articles about my hometown.

Blonder tongue was a well known vendor for regional cable tv network (analog) operator equipment, supplies, electronics. I think it still exists in some form for video mixing/live studio broadcast equipment.

https://www.blondertongue.com/

I work in a lot of nursing homes and their in-house "cable" systems are almost universally a rack full of DirecTV receivers connected to a rack full of Blonder Tongue NTSC modulators. I would have to assume similar systems were common in all sorts hospitality environments in the past, and only survive in nursing homes because most of the residents don't care about HD and might not even want it.

Also white labelled so e DishNetwork receivers with a few mods: https://www.youtube.com/watch?v=jBf3dZUAImk

The is probably how all jails and prisons are running their systems, too. Lots of these places still running CRT 4:3 TVs too. The 4:3/16:9 issues are rampant. And obviously the picture quality is just like you remember from the 1980s.

On a only slightly related note, there's a thriving collectors market on ebay and other places for "clear plastic" see through enclosure prison CRT TVs since they're both a novelty, and nobody makes CRTs anymore. People buy them to hook up to like Sega Genesis, Super Nintendo bare metal hardware for retro gaming.

It's getting harder and harder to bring them home. The prisons are trying to keep the items inside the system, even though the prisoners actually bought the items outright.

Like industrial equipment - you know it’s going to be good when it has an absurd name (company or model). Assuming it’s been around awhile.

Ah yes, South Bend is too close to Chicago, too close to Indianapolis, too close to Detroit... No VHF frequency left to allocate! The biggest problem is Chicago. South Bend is on a subcontinental ridge, with an average elevation nearly 300 feet higher than Chicago, and with all the transmitters in Chicago up 1500-1800 feet above ground and close to the lake, overcoming the curvature of the earth limitations on VHF propagation is fairly simple. Anyone in South Bend with a large antenna on their roof would easily receive all the stations.

On the upside, that meant having two versions of CBS and NBC (I don't remember an ABC affiliate in South Bend) plus the couple of other stations. My cousin got his start as a weatherman on NBC in South Bend simply by them needing someone to fill in from time to time and him being essentially the only person they could find that grew up in South Bend but had gone off to study meteorology at a university that was very very good for meteorology.

It's funny how certain brands or bits of tech can feel almost legendary in one place but totally unknown everywhere else

Just for completeness, the screw tabs were for an antenna, the notorious rabbit ears if you were close to the stations, or one on the roof if you were farther away.

My time to shine! I still own an early square body truck with the 6.2L Detroit Diesel. The thing that stands out to me in this article is that the Suburbans shown are an earlier generation produced from 67-72. Those did not have a Diesel engine, however the 6.2L Detroit Diesel was designed to drop into anything with a Small Block Chevy, so I can see how these may have been retrofitted. In fact, these engines are still produced today in 6.5L form (see the AM General Optimizer) and are used in the HMMWV.

These really are very simplistic engines and simplistic vehicles in general. Mine has power nothing, at least electronically. The shifter really is comically large and very inconvenient to whoever sits in the middle. The highest gear is third gear.

Powerful? No, not really. But surprisingly efficient for the size. Reliable as well.

The original castings were pretty poor in the 6.2 and 6.5 and lots of them crack at the crank webbings. This is supposedly fixed in the AM General blocks. They were common work trucks in the PNW (forestry, mining) but while you see the old Cummins or Ford IDI's around still the "Detroit"'s (no relation to the 2 stroke Detroit or Series 60) are quite rare. My family still has an early mechanically injected 6.5 that's held up OK though (~300,000km on it).

I'd say that 6.5 as plenty of life left. My 6.2 is pushing 400,000km.

the 6.2 and 6.5 are good engines - but dodge has the cummins and the ford powerstroke (other than the 6.0) are a much better engine and so they get a bad reputation.

Came to say 6bt aka the 12 valve must be a contender

The 6.0's problems are solvable. It's the 6.4 you really need to avoid.

The 6.2/6.5 were gm engines not detroit diesel. very different engenes.

Detroit Diesel was a division of GM at the time: https://en.wikipedia.org/wiki/Detroit_Diesel#Origins

https://en.wikipedia.org/wiki/Detroit_Diesel_V8_engine

I once swapped an OM617 (the 5-cylinder turbodiesel used in many 80’s Mercedes sedans) into a 67 Chevy pickup.

Once started, the engine would run with no electrical system at all! Even the fuel shutoff operated on vacuum.

https://youtu.be/5teg3Zlj0bo

https://youtu.be/q8LEWIZi21Q

https://youtu.be/kuDcSuwdzaw

https://youtu.be/MqWwUC3h3VU

By far my favorite hack :)

That's really interesting, but I'm curious to know if that amount of vibration is expected. It seems like something isn't mounted correctly from the videos.

Yes, that level of vibration is not normal, and is due to the fuel injection pump being out of adjustment. Because the fuel regulation is mechanical, it is possible to develop this sort of resonance. If you google for "OM617 rack dampener bolt", you'll find lots of forum hits about it. This video was taken before I was aware of the cause.

You must get a lot of questions (or confused looks) when people see that thing still running! The simplicity of those engines is kind of a lost art these days. Everything now is so computerized that you can't even diagnose half the issues without special software.

Whats very coincidental is those suburbans in the article are on the Wikipedia page for that generation: https://en.wikipedia.org/wiki/Chevrolet_Suburban#Sixth_gener...

> The highest gear is third gear.

Was it the strait 3 speed or the 4 speed with a "granny gear" aka the stump pulling L - Low range? 4 speed should be the Muncie SM465 which I had in a GMC 6000.

It's the 4 speed with the granny low gear.

Today, in the Murchison Radio Quiet Zone:

  The Power and Signal Distribution (PaSD) SMART boxes (Small Modular Aggregation RFoF Trunk) are an essential component of the Square Kilometre Array Low frequency (SKA-Low) telescope, currently under construction at Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory, in Western Australia.

  The SMART boxes provide electrical power to the SKA-Low telescope's 131,072 antennas and collect signals received from the sky to go off-site for processing.

  [ .. ] “The ‘radio quiet’ results that the ICRAR-designed SMART boxes achieved were to the highest standards in radio astronomy. A mobile phone on the surface of the moon would cause more interference to the antennas than the SMART boxes that sit among them,”

~ https://www.australiandefence.com.au/defence/cyber-space/icr...

I still haven't found any vehicle guidelines for the Inner Zone ( 70 km radius ), but for anyone with an interest:

* General introduction: https://www.industry.gov.au/science-technology-and-innovatio...

* Restricted airspace: https://www.avsef.gov.au/consultations/restricted-airspace-o...

* Limits of intereference by frequency and distance table: https://www.ursi.org/proceedings/procGA11/ursi/JP2-17.pdf

RF over fiber is a fairly well established thing, it's used in two way data satellite earth stations to convert a L or S band signal into something that can go a longer distance from the antenna to a conditioned equipment room at the same place.

https://www.vialite.com/market-sectors/satcom/

https://dev-systemtechnik.com/rf-over-fiber/

Very cool. Is there a reason the RF has to be converted back to RF after the fiber link vs processing the RF spectrum data optically?

your typical satellite modem will have an RF interface either somewhere between 70 to 140 MHz (where it's intended to be upconverted/downconverted by the LNB and BUC/SSPA at the antenna), or somewhere between 1100 to 1900 MHz, both intended for attachment to low loss coaxial cables. This works fine if you're putting the modem fairly close to the LNB and BUC/SSPA. If it needs to be a hundred meters away or something, it's a lot of RF loss, and path loss/link budgets in geostationary satellite are already hard enough without introducing any more loss at the ground side.

https://www.comtechefdata.com/products/satellite-modems

I would imagine it's because electrical amplifiers, filters, and other such items are cheap and well understood. Whereas optical amplifiers, filters, and other such things, particularly ones that operate at low-GHz frequencies are expensive and kinda wild

well, an optical amplifier wouldn't do anything at all attached to a waveguide into a feed horn, in something like a 6.3 meter ku or c band cassegrain antenna design antenna aimed at a geostationary satellite... that's the job for a BUC/SSPA. You need. it needs to be RF.

rf over fiber in a satellite teleport application is more about being able to separate the modem from the antenna-mounted LNB and BUC/SSPA which might be some distance away.

> Before retiring from NRAO (years after my interviews with him), Mr. Sizemore outfitted a new Dodge Ram extended cab truck as an RFI vehicle, a feat which was written up in USA Today.

Dead link but luckily archive.org has it.

https://web.archive.org/web/20140725075606/http://usatoday30...

> Here he monitors the gross violations of the Quiet Zone and also looks at the local environment: powerline noise, illegal use of radios, etc. For example, at the time of my visit there, the amateur radio bands were being used improperly by a group of people and the signal was strong enough to overload the 140-foot telescope, so it became a serious problem... The likely action taken will be that he calls the FCC in to enforce the rules in place. After 20 years on the job, Wesley has built up a network of contacts he can call upon when he needs help. One of those contacts is the man in charge of the Enforcement Bureau at the FCC, whom Wesley knew when he was still a satellite technician.

Always interesting to hear examples how effective coordination often comes down to networks of people-connections that get built up over time. Software folk often think it's simply automating whatever process -- I certainly thought that early on -- but more and more I'm seeing it's about knowing the person in the right role with the right experience. Your personal network is leverage.

The last two sections about helping out a grumpy farmer with an old burned out amplifier and coordinating secret fly-overs with the Cheyenne Mountain guys are also great people-network stories.

I wonder how many of his critical contacts at the FCC have been fired by Musk

I live in a town that has some pretty huge military radars (S- and X-band radars), and while they are pointed away from the population - the side lobes still send out a periodic chirp that has the duration of exactly 10.5 seconds, and it is only audible in audio equipment.

And for guys like me, that operate a home recording studio, it really fucking sucks.

Another place I lived, there was this 7 kHz noise that would also get on top of any amplified source - almost drove me insane, and could never figure out what it was. It was some kind of RFI. At first I thought it was something related to the house, maybe a bad ground combined with some switching circuit.

Turned off the mains breaker, and hooked up my guitar to a battery amplifier - same annoying noise was present. Tried shielded cables, tried cables in different lengths from longest to a short 5 cm patch cable, still there. Went outside, and it was present. No distribution transformer, gas meters, or smart meters in general.

Also, back in the day, we'd get Soviet TV coming in waves - meaning that you'd get some periodic interference where your TV would show a combination of both. I think it was due to their huge over-the-horizon radars.

(But I've never had any problems with RFI from cars!)

Are you in Alaska?

I spent two weeks there, during the commissioning of the Green Bank Telescope (GBT). Our team was designing the monitor and control system for an upgrade for another NRAO telescope, the Very Large Array in New Mexico. The team from the GBT led us through their design during the day; our nights sleeping in the on-site dormitory, complete with the break room where Frank Drake came up with his Drake Equation estimating the number of extraterrestrial civilizations...

Those old diesel trucks!

The GBT is so big, it's just wrong. Experiencing the forest moon of Endor, in real life.

(The single-dish GBT is sensitive to near-field RFI, whereas the multi-dish Very Large Array is a bit more tolerant. The VLA isn't restricted to antiquated diesel vehicles. Although they do ask visitors to power off cell phones and refrain from any microwave ovens that RVs might bring in.)

This is an awesome article. I'm a HAM in an urban area trying to figure out how to operate in the mess that is my EM spectrum with low power gear. It's a fun challenge, but having some quiet would be nice!

I haven't had the pleasure of seeing this site, but I did have the opportunity to visit Sugar Grove Station (not too far away) while it was in operation. I had a friend stationed there while I was nearby, and took a detour to spend the weekend at his house on the base.

Seeing the massive old radio telescopes and the tracks they used for positioning them was something else. The scale is hard to communicate; it's kind of like the first time you get up close with a Navy Aircraft Carrier. It's hard to fathom just how BIG they are until you are next to them.

Were you allowed on base? What was your experience like and your perception of what was going on?

I had the opportunity to perform a bat survey at Sugar Grove, and a poor guard had to come out to keep an eye on us until 3am because we couldn't be left alone. We noted curious wooden gazebos positioned around a featureless meadow, hinting at significant manned infrastructure underground.

Unlike the Green Bank Observatory from the above article, Sugar Grove was piggybacked on the National Radio Quiet Zone so the NSA could intercept intercontinental telecom traffic as a part of the ECHELON network. The cover story was that it was a run-of-the-mill AT&T site, but was an open secret for all the Pendleton County WV locals that it was a spy site. The base was also home to the best restaurant in the whole county, which isn't saying much for a single-traffic-light county.

https://en.wikipedia.org/wiki/Sugar_Grove_Station

https://en.wikipedia.org/wiki/ECHELON

Yes; I was cleared to the level required (but not need to know) and the visit was approved by his (the base) CO. He was stationed there as a Crypto Tech, and though I couldn't see the really neat underground stuff I was mostly free above ground as long as I was chaperoned by him. He gave me quite the tour.

The gazebos are there due to the underground facilities, yes. There is likely a whole lot more than even you realized.

As for my impressions: I was a Security Manager for a more operational side of the Navy for years (later). I informed a lot of my edge case thinking with what I saw of how they handled things there. I don't know that I really want to go into more detail than that.

Wow, I really appreciate your fascinating reply, thanks!

I can only imagine what it must have been like standing next to those giant dishes and realizing just how massive they really are

The NRAO should kickstarter a new, electronics free diesel fullsize.

Not to build it, just to prove how much demand exists for it. Because this is something every truck guy I know has been asking for forever.

There's even an online rebellion of sorts over the new Hilux not being available here.

When has the hilux ever been available here? I've wanted one for over 20 years, but not enough to pay to import...

Not ever. But apparently there's some new model called the Champ that starts around 10k, and has people who want simple trucks raging out. For good reason, it's a solid looking simple truck.

We’ll need to fire all the industry plants in the EPA before we can legally have a small (fuel efficient) truck here in US. Our emissions laws were written by Big Truck.

has this not happened yet? I don't have a twitter account so i can't ask

No, and even if it were to happen car manufacturers can’t make 4+ year plans based on policies the next bonehead in chief might just revert.

We need a mass popular movement to dismantle the EPA as they stand and rebuild them with an actual purpose.

This isn't argumentative. Do you have anything i can look at to see why the EPA et al would not want a light, cheap, fuel efficient truck?

is it capture by Ford and GM? Are there even trucks as small as the Nissans that had the 2400 motors (or 2600)? I live near enough texas that every truck is way too big, so i don't see many new, small trucks. A lot of people have the old, nearly all metal, small trucks.

> i don't see many new, small trucks

Right, because the EPA has made them illegal in favor of larger, less fuel efficient trucks. This paper covers the topic well^, you can also see many examples searching online for “EPA Small Truck Footprint”.

^ https://meche.engineering.cmu.edu/_files/images/research-gro...

Hey, thanks for replying! I read the title of that paper and immediately knew what it was going to prove. I have a recollection about this from 10 years ago, but for some reason it didn't comport with "it's the EPA's fault we can't have nice things"

you'd think the https://www.nhtsa.gov/ would have something to say about regulations encouraging increased "box height" or grille height; which results in worse outcomes in nearly all accidents (could be all, but i don't feel comfortable asserting that.)

sorry it took me five days to notice you replied.

> electronics free diesel fullsize

I'd happily settle for embedded computer free anything. Or even just not-cell-network-connected and no touchscreens. The bar has dropped quite low at this point.

An old-school, no-nonsense diesel truck with zero unnecessary electronics? I feel like it would get funded overnight

many electronics actually improve safety a lot, so probably not a great idea.

I grew up in this area of West Virginia, it's such a crazy thing that a community of really amazing scientists are nestled in the middle of this incredibly rural area. It's really neat to see the old blue trucks if you take the tour, and the Cass Scenic Railroad is just nearby and gives a really beautiful view of the telescope array. The National Youth Science Academy Camp is also surprisingly located nearby, it was wild as a kid knowing that this batch of future scientists were flying in from all over the country and once I learned of it I wished I'd studied a bit harder. Such a beautiful, strange place.

One of my favorite parts about the old perkins diesel engine in our boat is that you need to press a button to stop it from running once started. You turn off the ignition and it just runs on physics until you do something to interrupt the fuel or air supply.

Diesels diesel (the verb). It keeps them exciting.

I’ve been in a friend’s car while it ran away on motor oil passed by a failed turbo. Turning it off didn’t stop the engine.

The scariest story I've heard was a parked diesel pickup truck going runaway acceleration because of the hydrocarbon vapours in the air due to an industrial accident.

They abandoned the pickup and it subsequently got blamed "A diesel pickup truck that was idling nearby ignited the vapor, initiating a series of explosions and fires that swept through the unit and the surrounding area".

I read about it in one of the disaster reports about the Texas City BP refinery explosion. Ugly mistakes were made.

> I read about it in one of the disaster reports about the Texas City BP refinery explosion.

Relevant part of USCSB accident reconstruction animation: https://youtu.be/goSEyGNfiPM?t=550 (but worth watching the whole thing!)

Can't quite call it parked if it's idling...

In 2006 my friend and I decided to stop talking about visiting the NRAO and actually go. We picked a weekend and then discovered that that Sunday was the 50th Anniversary open house! There were special exhibits and more of the facilities were open to tours than on regular visitors days. I can highly recommend visiting if you get the chance.

Coincidentally, my friend's last name is Blonder! And he's related to the Blonder-Tongue founder. According to my friend, all Blonders are related, the family name was originally Gottlieb, but was changed to something more Anglo sounding, to avoid anti-semitic discrimination, probably when they immigrated to the US from Russia.

It's a shame we don't better contain all the EM noise emanating from our modern vehicles.

I'm dealing with this issue right now on my boat (EM noise from hydraulic trim pump for the drive leg is coupling to a power supply line running to a more sensitive electronic component).

I imagine that there will come a time when they’ll need to revert to horse and wagon transport at the site. Or perhaps lay down railroad tracks and use cable cars.

You can buy what is basically the same engine new. https://quadstartuning.com/products/amg-gep-optimizer-6500-l...

They could get one of these https://www.offgridweb.com/transportation/toyota-gibraltar-t...

> Land Cruiser

Not a great idea, those engines like to blow holes in their pistons...

Up until the 2000s diesel engines in cars used mechanically controlled injection. With those, once started, the engine will run without any electronics.

Engines produced for industrial applications (such as tractors) in developing countries still use this, as it's a lot simpler and more reliable. Military trucks are the same. Just don't tell the EPA.

I have a 10kW diesel motor that doesn't have any wires at all, no battery. It's my SHTF generator for my well.

I might have to wind a generator motor if the reason stuff went bad is because of emp, but otherwise, yeah, you can buy 100% mechanical diesel engines still.

It is possible, but fortunately still exist countries like Ukraine, and produce old diesel engines for trucks (KRAZ) and for tanks (T-64 line, including T-90, and also used on military trailers like MAZ-537, so when you cannot visually see, you don't know if tank running itself or on trailer).

Main problem, in those countries have not managed to produce small diesel engines for light trucks, and KRAZ engines are something 6L or more (tank diesel are 10L).

I hear they made half-block near-flat modification for armored personnel carrier, and even used it on low-floor city bus, but as I know they was not much market success, so have not produced big series.

In eastern Europe in 80-90s produced small trucks with analog diesel engines, but as I know most enterprises already scraped and most lucky now producing WW or Renault by license.

I wonder if any of the currently produced cars will have seats still comfortable after so many years. Probably, no.

My 1986 early model E30 leather sport seats are still nearly perfect.

1987 E30 owner - even after getting the mold out during a restore, and in spite of a crack in the bolstering, the E30 sport seats are the _second_ most comfortable I've had the pleasure of owning. The seats in these old cars definitely have something up on modern leather seats, even its 27-years-older brother (4-series) that I drive daily.

The champion in that department, though, was the 1986 Volvo 740 that I briefly owned. Those seats were perfect in nearly every way.

Hell yes. I've always wanted to get one of those Volvos. It's wild because when you sit in the E30 you can feel that the seats should be shit, but somehow they are still in perfect condition.

The most comfortable seat I've ever driven in was the Honda element seat. Like sitting in a cloud.

The seats weren't really all that comfortable to begin with. However, you can rebuild the seats. LMC Truck has rebuild kits with new foam and covers. You can even add heated seats.

So there are good reasons, aside from reliability, efficiency and ease of repair, for having a 1981 Diesel Chevette with a 100% mechanical engine :)

Those are what you need after an EMP blast.

Grew up around some farm trucks that were electronic free diesels. My grandfather called them "luddite diesels". Later in life I realized the humor, considering that a diesel engine is a technology, and that luddites likely prefer horses...

No, the technologies that the Luddites disliked were very specific and regional. They only cared about machines that threatened their own personal jobs, not anyone else’s job.

Okay, loomer.

If you were a Luddite horse farmer or yoke maker you might hate diesel engines lol.

No, because those specialists never quite existed. That is, every farmer who owned horses would let them breed and then sell most of the foals every year. Similarly, any farmer could carve a yoke whenever they needed one; it wasn’t skilled labor that required years of training the way lacemaking or weaving was.

...it's just some fun conversation.

I think the Amish are closer to what people envision when they hear the word "Luddite", but luddite these days means anyone who is wary of or eschews technology. It was specific to the textile workers, originally, destroying machines.

This is definitely a neat place to visit. No digital cameras are allowed past a specific point, even. I have snapshots from walking the main loop with my dog from a few years back posted here:

https://vgeek.net/gallery/index.php/category/103-green_bank_...

I suppose they removed the alternators, and that's why they keep them plugged in?

No, they were plugged in to supply power to the block heaters. These kept the oil warm so they were easier to start.

Diesels use glow plugs to heat the cylinders prior to starting, to explain why sibling mentioned needing to keep them warm. Luckily resistive heat doesn't make RF noise, at least not that I've noticed. But they could also garage them with potbelly oil burners, too.

Green Bank is great. I have ties to E WV and made a trip there one time after hiking Seneca Rocks. Highly recommended if you get a chance.

https://ibb.co/N2RYW8vr

Since the unwanted interference is from sparkplug, I wonder - assuming it would contain no additional electrincs, could they get some EV? Or does the electric engine itself generate noise by necessity?

EV are so noisy they talked about doing away with AM radio in the US because the EV jams it.

I am unsure what would lead to this question...

hm, yea, I guess it was a dumb question. Spinning magnets for sure must generate noise.

It's possible to deal with it, but one must want to deal with it, plus the "costs" like increased weight, BOM, etc.

EV makers don't want to and it's a problem even with the very low bar is consumer equipment

yea, my question was more about whether this is more about the redundant additional electronics in newer cars, or just EV car problem in principle.

Mostly EV components - the motors and inverters that drive them can generate a lot of EM noise.

That's not because they have to, though; especially if quietness in a narrow band is required. It's just way cheaper and somewhat more efficient to abuse the motor as the inductor to filter the hard switching.

explain how you make something quiet in a "narrow band" around things that are so sensitive that it was claimed that "if you integrated all of the signal power received by the antennas, it's less than the energy used by a flea to jump".

not just at any given moment. In the career of whoever said that, the total power was that miniscule.

It's possible to build a control system and inverters for an electric vehicle that don't spam RFI everywhere, it won't be anywhere near as small, as all the filtering required is going to be quite sizeable. (And no, I'm not suggesting using analog/linear systems, that would be silly huge and get super hot)

The motors are brushless, so if all of the drive power is low frequency and well filtered, it'll be nice and RF quiet.

I wonder how they start them. Park at the top of a hill?

That's one way, but I suspect that even if they did disconnect the alternators, they could just charge the batteries overnight.

On the other hand, alternators should make way less EM noise than ignition coils.

I feel like they could probably buy some 80s Mercedes 300d and get newer cars with lots of parts available as there's junked ones everywhere.

But the ECM?

What ECM? They're mechanically injected diesels. The main purpose of the electrical system is to run the starter to crank the engine. And maybe headlights and stuff.

They're very simple cars.

Yep to parent poster look at the fascinating mechanical fuel pumps in some detail they are incredible machines in their own right

Direct injected gasoline engines have a high pressure fuel pump (in addition to the electrical low pressure) mechanically powered by the crank

My Diesel has an analog glow plug controller. That's literally the most complicated electronics in the whole car.

I would argue the 6.2L/6.5L Detroit Diesel is a superior choice in North America, which is the engine used in the article.

The 5.9L 12-valve Cummins is also a fine choice. Another fully mechanical engine. In theory, with a manual transmission, you can operate a vehicle without even a battery after it's started.

Well, almost. The 5.9L fails safe: there is a fuel shutoff solenoid which operates in reverse: you give it power to keep the fuel flowing. You’d need to modify it to force the solenoid open (or remove it).

The OM617 (as used in many 1980’s Mercedes sedans) fuel shutoff operated on vacuum, and once started, the engine would run with no electrical system at all.

The bit about the old diesel cars still being in service because modern ones generate too much RFI is both fascinating and a little surreal

I wonder what signal processing methods exist to deal with terrestrial noise sources instead of relying on the brute force approach.

Not sure what you mean by the brute force approach. The problem is that the terrestrial noise sources are many orders of magnitude stronger than the faint signals that the ultra-sensitive receivers are designed to receive, and easily saturate them. The only recourse is to excise any data taken during an RFI episode. It would be extremely difficult, if not impossible, to do science in many RF bands of interest were it not for the NRQZ.

Not who posted the parent comment, but "brute force approach" = having the NRQZ I'd imagine.

I figured as much. The question about why it is needed brought to mind something I was told when I started work there, over three decades ago. It was something along the line that all the signal energy recorded by the observatory’s telescopes integrated over their lifetimes amounted to less energy than is expended by one flea making one jump. I don’t know exactly how accurate that is, but it does rather vividly illustrate the problem.

Well, for fun, that's 2.25 ergs, over 30 years that's an average of -126dBm

That's not that low for signal processing these days, and it'd be much more practically useful to develop the ability to filter out noise to that level than attempting to suppress it over a very broad area. My understanding is that it's the sensitivity of the detectors that's the real issue: they get pushed into clipping since their dynamic range is not that high. A similar thing happens with optical transceivers.

[0]: https://journals.biologists.com/jeb/article-abstract/47/1/59...

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