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30 July 2013

Radiated Emissions Control

NRAO = National Radio Astronomy Observatory:
NRQZ = National Radio Quiet Zone - Map:

Note: "banned digital cameras down range after they proved quite noisy."

A writes:

I've spent a fair amount of time at NRAO over the past twenty years. And was staying in their on site housing about a week ago. Fiber is their main weapon against radiated emissions. All the dorm and visiting scientist quarters have fiber transceivers in the rooms and shielded ethernet cables to plug into laptops. There's a lot of signage about turning off WiFi and cellphones.

Might as well turn off cellphones. NRQZ starts around the Virginia / WV state line. As you cross successive ridges coverage disappears. NRAO is about 45 minutes drive time from cellphone coverage. Driving south from Green Bank cellphone coverage is regained near the Greenbrier Hotel / bunker near White Sulphur Springs, WV, also about 45 minutes south. Sugar Grove is northeast of Green Bank and well within the protection of the quiet zone.

The observatory itself takes fairly strict measures to reduce RFI/EMI/EMC issues on the site. Employees sign that they won't have a microwave oven for instance. And on the facility the two microwave ovens I know of are inside a metal Lindgren screen room style enclosure

The observatory actively hunts down interference in the surrounding community with a mobile communications truck. I have pictures of the surveillence truck if anyone is that curious.

The lab PCs and test equipment still make up a lot of the low frequency hash on site. The antenna control room, signal processing room, computer rooms, and visitors center display area, are all screen rooms with multiple layers of copper screening on windows and seam soldered copper foil in ceiling and under floors. The 100 meter antenna operates from 300 MHz to around 100 GHz with cryogenic front ends downconverted into the 1~8 GHz range for the two mile trip across site to the signal processing and control room area.

And yes the on site diesel vehicles were vintage Checker cabs until recently

This year I've seen a few diesel Ford trucks now join the facility stable of vehicles. But that's only beyond the "No Spark Plugs" sign and gate to the actual antenna area. They also banned digital cameras down range after they proved quite noisy.

Most observing worldwide is done remotely today whether optical or radio. So data is captured and then sent to the end user via Internet or tape or hard drives. There's a fiber link from NRAO to University of Virginia NRAO Lab where it connects to Internet backbone. I know when we've streamed meeting video live, it was multicast from Charlottesville to minimize the bandwidth back to NRAO-GreenBank.

The town of Green Bank (population 143 ), which really is a subset of Arbovale WV, is very small -- 531 people

So back to the original question, the observatory probably has more phones than the surrounding community. Don't know for sure that they source the bandwidth, but wouldn't be surprised since that would give the observatory access to whatever bandwidth wasn't being used at any given time.

And the concept of living in the NRQZ to avoid surveillence is of course just Hollywood ignorance of all things technology related. However if that person was off grid, had no phone, living in an underground home, in the NRQZ that would be a good start to being invisible. If it's not "the middle of nowhere", you can at least see it from there.