Chasing RFI Waves – Part Seven

Here is part seven (the final part) of my non-fiction work about the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia. You can also read parts onetwothreefourfive and six.

The NRAO fleet

The cars used on the NRAO campus are different from what you might expect. You’ll see photos of them below, and in case you’re wondering why they look so old, let me explain.

Gasoline-powered cars generate more RFI than diesel-powered cars because they have spark plugs. That meant that NRAO had to purchase diesel cars when they bought their original fleet, and by the way, these cars are part of that original purchase. When NRAO wanted to renew their fleet, they found out they couldn’t, because the newer diesel-powered cars on the market were all using chips and various other electrical equipment (seat belt buzzers, door buzzers, etc.) that generated unwanted RFI. Any electrical ark (spark plugs, power lines, bad thermostats, etc.) generates broadband radio signals, at various frequencies throughout the spectrum but mostly at the lower frequencies, below 2 GHz or so. So that meant they had to stick with their original fleet, whose diesel engines used no computer chips whatsoever and generated little RFI. You may look at these cars and call them clunkers but to NRAO technicians and scientists, they’re reliable modes of transportation that do not interfere with their research.

You may see newer cars in the parking lot, but they’re not used on campus. Only these blue diesel cars can go under and around the telescopes without causing problems.

Because they have no new technology to warm up the engine block on cold mornings, they keep them plugged in whenever they’re parked, to make sure they can be started right away and to keep down on the wear and tear on the engines.

We were ferried around the NRAO campus in one of these cars by Mr. Sizemore, and they’re quite comfortable.

One thing I can’t get used to in these old cars is the gear shifter. It’s so long and seems so awkwardly placed…

More on the telescopes

One of the telescopes on site is used as a teaching instrument. NRAO, being involved in both research and educational efforts, brings groups of school-age children on-site to teach them about radio astronomy. The telescope is not a fancy, cryogenically cooled machine but a simple wire-mesh dish with simple control and monitoring gear that the kids can play with. It’s fully functional though, and it does pick up many radio waves. It’s sufficient to teach radio astronomy and galactic coordinate systems and such.

The National Youth Science Camp is just up the road from NRAO. For two weeks each summer, groups of teachers (high school and college) come to NRAO for an intense course in radio astronomy. The staff turn on the knowledge firehose and “really pour it on them”, as Mr. Sizemore puts it. They have classes during the day and then do research at night with the telescopes. He says it’s not unusual at the end of two weeks to see them walking around the campus, muttering to themselves.

After they complete the course, they can bring their own students to NRAO (for a day or so) and use the 40-foot learning telescope to teach them about radio astronomy without much intervention from NRAO Staff.

As the young researchers sit and wait by the telescopes for the stars to come into position, they have nothing to do, so they doodle or draw. Sue Ann Heatherly, the NRAO Education Officer, loves to collect the better ones and she puts them up on the walls of various NRAO corridors.

As we drove around, Mr. Sizemore pointed to a dish and told me it was a polar mount, and that I will never see a dish built like that again. It’s mounted on the plane of the galaxy (Milky Way) not the earth coordinate system. It’s a right ascension and declination mount. If you were to stand on the axis of the telescope and look at the sky, you would be looking directly at Polaris, the North Star. (By comparison, the GBT (Green Bank Telescope) is mounted as an elevation and azimuth drive system, which is an earth based system. ) The reason this telescope was built like this in the 1950s is because computer power at that time wasn’t fast enough to translate between the coordinates of the galaxy and the solar system in realtime. Now even a pocket calculator can do it.

Although the telescope has been sitting unused for 10 years, they recently brought it back online in order to do atmospheric research studies with MIT. The study involves bouncing radio signals off the satellites around the Earth, then measuring those signals to see how they were perturbed by the atmosphere. The MIT researchers brought their own trailer on-site, with their own receiver and computer equipment. After some work mitigating RFI leaks from the trailer, they were ready to go and NRAO was happy to see the telescope back in action.

When it comes to the GBT (Green Bank Telescope) one of the things NRAO doesn’t want to do with such a large telescope is to set up vibrations in the structure when it’s started and stopped. The way they handle that is to mount both forward and reverse motors at each drive wheel. In order to stop or start it, all the technicians have to do is to increase the current on the motors that move in the direction they need, and the structure will stop or start as fast or as slow as they want it. When you think about this and other precision equipment mounted on the dish, like the laser leveling equipment and the motors that power each plate in the dish, Mr. Sizemore likened the GBT to “building a battleship with the precision of a Swiss watch”.

Even the track of the telescope is leveled to within 1/5,000th of an inch, and the rest of the structure is comparable to that all the way up. What about the land settling over time, I asked? There are no such problems, he replied, because they went all the way down to bedrock when they laid the foundation (about 40 feet).

The local cement contractor had no competition when it came to the contract for laying the foundation. The closest competitor was about 40 miles away, on the other side of the mountain, so he got the contract and had to rent three additional cement mixer/pouring trucks in order to keep up with the demand. For the entire period (three or four weeks) that it took to pour the foundation, the man kept grinning as his trucks pulled into the construction site, because he stood to make a lot of money.

The NRQZ monitoring station

While I was on-site, Mr. Sizemore showed me his “hiding place” – his monitoring station. It’s a big trailer that can be hauled from place to place, but has been made stationary and hooked up to the power lines. That’s where he does most of his work. 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. Wesley told me that the problem will likely be taken care of long before I write up about it, and 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.

While I was recording our talk, I asked Wesley if he could see the interference generated by my recorder, and he worked up a quick setup to find the noise it created. Sure enough, he tuned into the noise generated by my iPod as it was recording our conversation within a couple of minutes.

One of the teaching tools he uses with school groups that visit NRAO is a metal trashcan (a Faraday cage with an antenna and amplifier mounted inside the lid). He takes his spectrum analyzer, connects it to the antenna and amplifier assembly, then gets a student volunteer to put in their phone or laptop or MP3 player, then he shows the whole group the interference those devices create. The only thing the antenna sees is the RFI generated by the device put in the trash can, because it’s a Faraday cage. Everyone is invariably wowed by this.

As we drove around the NRAO campus, we came across a car with a “cantenna” (a directional waveguide antenna for long-range WiFi), and I immediately pointed it out to Mr. Sizemore, as I knew he’d be on the lookout for WiFi transmissions in the area. Smirking, he admitted that was his service car, and he told me the story behind it. The FCC had donated it to NRAO, who had been using it to sniff out illegal transmissions. The car actually had antennas built into its roof and was already fitted with equipment for sniffing out radio transmissions. Mr. Sizemore outfitted it with WiFi “sniffing” equipment as well: a laptop with NetStumbler and a bunch of other apps, a GPS device for marking the location of RFI-causing WiFi and a “cantenna” on the roof, that he could rotate and point at various WiFi sources.

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.

NRAO and the community

As we drove around the campus, Mr. Sizemore pointed to the farmhouses that surrounded NRAO. When the government took over the land, they invoked the right of imminent domain, forcing the farmers to move. That generated animosity toward the observatory, because the land was fertile and it was good for farming.

With time, things got better, to the point where there was only one farmer left who couldn’t stand NRAO and wouldn’t ever let them step on his property. All of the powerlines and phone lines for NRAO were routed around his property. At one point, the man chased Mr. Sizemore’s predecessor off with a stick. If NRAO staff ever had to go visit him, they’d take a deputy sheriff with them. When Mr. Sizemore began working there, he knew to steer clear of the farm.

One day though, he got a call from the man. He had an outside TV amplifier, a tube-type amplifier made by a company called Blonder-Tongue, which had been struck by lightning. The old man couldn’t find anyone to repair it and he didn’t want to spend money to get a new one. He called the only one whom he knew could help. Mr. Sizemore was of course glad to do it, because he’d finally be able to atone for the bad blood between NRAO and the farmer.

He drove out to the man’s place, where he had to wait off the property for the amplifier to be brought to him (he still wasn’t allowed on the farm) and took it back to the lab to see what he could do.

He called Blonder-Tongue and was told they hadn’t made that amplifier model in 20 years, and they hadn’t serviced it for 10 years. They didn’t think they could help. Mr. Sizemore insisted he speak with a supervisor and as luck would have it, the repair supervisor was an elderly guy who remembered working on them when he’d started with the company. He said, “Send it to me, and I’ll show these young technicians how things used to be.” Mr. Sizemore explained the entire situation to the man, about NRAO and the farmer, then mailed off the amplifier to the repair supervisor.

The amplifier came back repaired and it didn’t cost anything either. The old farmer was elated when he got it back. He put it back up and everything was fine until a week later, when he called Mr. Sizemore. You know the old saying about lightning not striking twice? Not true for the old man. His amplifier had been struck again.

He didn’t want to let Mr. Sizemore examine his property, to see if the lightning strikes could be prevented, so all he could do was to mail it off to Blonder-Tongue once more. Sure enough, it came back repaired as new again, at no charge. Thankfully, to the day of the interview, the amplifier evaded other lightning strikes so things were fine between NRAO and the old man.

Thanks to Mr. Sizemore’s efforts, NRAO enjoys a very good relationship with the community. Being an isolated rural community, where all they have is each other, they tend to pull together and help each other.

For example, some people had learned to recognize the interference from awry TV amplifiers, which would show up as a herringbone pattern on their sets, and would call Mr. Sizemore to let him know. They also knew what powerline interference looked like, because it would show up on their sets once again, generating a specific noise pattern.

The NRAO site is basically a wildlife preserve. They let the animals live and roam free. The only practice they instituted a few years back was a controlled deer hunt, because the deer population had gotten out of control. Before they began, the Wildlife Management Institute wanted to do a headcount of the deer, so they fitted a plane with thermal imaging equipment and started to fly over the NRAO site one night.

Because they hadn’t publicized this, the local people didn’t know what was happening and all they could see was a plane which kept circling over NRAO at night. They thought the plane was in trouble, so they all pulled together, drove to the local airport (next to NRAO) and shone their headlights on the landing strip, to help it land. Well, after a while, they figured out the plane wasn’t in trouble and went home, but let’s just say that the next time WMI decided to do nighttime wildlife studies, they publicized it widely, to make sure everyone knew what was going on.

The NEACP encounters

As we talk about flyovers, another good story is that of the NEACP encounters. When the Cold War was going on, the US Military always had an aircraft in the air at all times, an airborne command post (NEACP: National Emergency Airborne Command Post). There were multiple such aircraft in service and one was in flight at all times. One would take off before one would land.

When they would fly over NRAO, all the radio equipment on board those planes (they used 1,000 Watt transmitters) would overload NRAO’s equipment with RFI. Mr. Sizemore found the number for CMOC (Cheyenne Mountain Operations Center) and spoke to one of the people involved with NEACP. He introduced himself and said, “You have this aircraft, using this callsign, operating at this frequency, at this location.” They got upset right away, because they didn’t want anyone to know what their routes were. They started questioning Mr. Sizemore about the source of his information, to which he simply replied, “I used a 300-foot telescope and I looked at your aircraft.” Then he continued to explain: “I have to track this source of interference down. That is my job. I have a solution. Let me send you my observing schedule every month, to tell you what frequencies I’ll be observing on what days and tell you my station, and then you’ll be able to avoid me. And if you can’t avoid me, you can let me know, and I’ll tell the astronomers to take a coffee break.”

As a result of that phone call, Mr. Sizemore got the NEACP to avoid the Green Bank area, and when they couldn’t avoid it, he got a few calls from them when they had to pass over NRAO, after which he would quickly tell the astronomers to take a break, as their equipment would soon get overloaded, making the data unusable.

That’s the end of part seven and the series. As mentioned at the start, this work is unfinished, and that’s why you don’t see a nice story arc with good closure, but I hope that what I’ve published has proven enjoyable and interesting for you and has sparked your interest in radio astronomy and NRAO. You can also read parts one, twothreefourfive, and six.

I’d like to once again thank Wesley Sizemore, without whom this text would not be written (or edited properly). Thank you Mr. Sizemore!

Thank you for reading!


4 thoughts on “Chasing RFI Waves – Part Seven

  1. Pingback: Chasing RFI Waves – Part One | RAOUL POP

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  3. Pingback: Chasing RFI Waves – Part Five | RAOUL POP

  4. Pingback: Chasing RFI Waves – Part Six | RAOUL POP

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