Engineer's Corner

Credit Credit: Ryan T Conaty

The Engineer's Corner is an occasional series penned by RIPR's IT & Engineering Director, Aaron Read.  

Any time he thinks there's something useful, important, amusing, or otherwise interesting enough to write about?  This is where you'll find it.  The highest compliment he gets, and frequently, is from readers who assure him that even though they have no idea what he's writing about, they love that he's writing it.

TheEC: Height is King for FM

Oct 24, 2012
Broadcast Peak in Santa Barbara CA
Aaron Read

By way of analogy, think of an FM transmitter as a big lightbulb on top of a pole. The taller that lightbulb is, the easier it is to see that lightbulb from wherever you are. The lower it is, the more likely it is that a hill or a house or a tree might block your view.

TheEC: Solar Outages

Oct 11, 2012

It has to do with our satellite downlink from NPR. We have a hefty 13-foot-diameter satellite dish, located in North Providence; there's no room for it at One Union Station! It points to "Galaxy 16," a telecommunications satellite in "geostationary" orbit that all NPR stations use.

"Geostationary," also popularly referred to as "geosynchronous," means that the satellite orbits the Earth in sync with the Earth's rotation...about 6800 MPH. That's pretty fast, but the key is that it's the SAME speed for both. So from our perspective here on Earth, the satellite just floats there, not moving, over 22,000 miles up in the sky!  To put that in perspective, it's like driving from northeastern Maine to southwestern California, SEVEN TIMES.

In Galaxy 16's case, the satellite is at 99.0 degrees west longitude, meaning it's fixed above a point on the equator over the Pacific Ocean, about 500 miles west of the Galapagos Islands (near Ecuador).

In general, geostationary orbits work great for communications satellites like for NPR, but there's a catch: twice a year there's times when the Sun, the satellite, and our dish all line up perfectly.  It's only for four or five days, and only for four or five minutes per day...but the Sun puts out so much energy on ALL frequencies that it completely swamps the satellite's own signal, so we lose all NPR, BBC and other satellite programming.

A common tech support request I get is for help with our stream/webcast from our listeners. The "digital illuminati" often like to claim that the web will mean the death of radio any day now, but streaming is still decidedly more complex and more tricky than radio's "push button, turn knob, get programming" simplicity.

Those iconic words, coupled with the tell-tale "brraaaaap... brraaaaap...brraaaaap" data tones, are widely known as the EMERGENCY ALERT SYSTEM, or EAS. Like its predecessors the Emergency Broadcast System and CONELRAD (CONtrol of ELectromagnetic RADiation), EAS is - at its core - a means by which the US Government can disseminate emergency information to the public at large in a short amount of time.

Wikipedia

Providence, RI – Not long ago we talked about "tropospheric ducting" for FM and some TV signals. This time on the Engineer's Corner, we'll talk about its cousin for AM signals: skywave!

www.comrex.com

Providence, RI – This time on the Engineer's Corner let's talk about CODECS. Short for "encoder / decoder," codecs are a fact of modern life; used in cellphones, digital cable TV, digital television, the internet, you name it! Anywhere there's data, there's probably a codec involved.

TheEC: Atomic Clocks

Aug 1, 2012

A somewhat radio-related topic this time on the Engineer's Corner: Atomic Clocks! At NPR stations, like Rhode Island Public Radio, we rely on precision timekeeping because we coordinate our local programming with NPR's national programming via each end paying attention to a very specific clock. Everything is timed down to the second and, in some cases, to half-seconds! We use a special clock system from ESE to synchronize all our clocks in the studios. Such systems are expensive, costing thousands of dollars, because of their very high precision. But at home you can get pretty close by using an "atomic clock", available at most Radio Shacks, Walmarts and other, similar stores.

TheEC: Tropospheric Ducting

Jul 24, 2012
Tropospheric Ducting
www.dxfm.com

Welcome to the Engineer's Corner and since it's high summer I thought we'd talk a bit about TROPOSPHERIC DUCTING, an interesting and unpredictable phenomena that happens when it gets hot out, say, the mid 80's and hotter. When an FM or TV signal goes out into the upper atmosphere, if it encounters air that is warmer, instead of cooler, the higher "refractive index" can cause the signal to be bent. If conditions are right, it can be repeatedly "bent" into a "tunnel" or "duct" and carried for hundreds, if not thousands, of miles. 

Pages