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."
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.