September 2013 – Page 2 – Engineering Radio

Stay sharp, do not be fooled

I am wondering what is going on with the HD Radio rollout these days. Particularly the all-digital AM conversion scheme being bantered about so often last spring. Not much is being discussed publicly about that or the AM revitalization. I have found FCC Commissioner Clyburn’s remarks at this week’s NAB Confab interesting. HD Radio is paid lip service here:

There are hurdles: if broadcasters do not broadly embrace the HD technology and the multicasting and other enhancements that it makes possible, listeners will have few incentives to buy digital receivers. Likewise, if no consumers own digital receivers, then there is no reason to broadcast in digital.
But I’m not worried. More than 15 million digital receivers have been sold so far, and that number will only rise. Thirty-three auto manufacturers include or plan to include digital receivers in their cars, and those receivers are standard equipment in over 80 models. This will dramatically increase the number of digital receivers in the coming years.

But in the solutions for AM broadcasters, HD Radio is not mentioned at all. What is put forward as a six (actually five) step plan to revitalize AM radio turns out to be some rearranging of the deck chairs and a little more. Cliff notes version for the FCC’s AM revitalization:

Open a one-time filing window for AM license holders to acquire an FM translator
Relaxing community coverage rules for AM licensing allows greater flexibility for transmitter siting
Eliminating the “Ratchet Rule” used in nighttime allocation studies for new facilities
Permitting more widespread use of MCDL technologies by eliminating STA requirements
Reducing minimum field strength requirements by twenty-five percent allowing the use of shorter towers

While those options may save an AM license holder some money, none of them do anything to improve the technical quality of AM broadcasting. Several of them (#2, 4, and 5) will, in fact, if widely implemented, reduce signal levels over cities of license, making electrical noise and interference problems more prevalent. This is a step in the wrong direction.

These points are basically a rehash of some of the MMTC’s (Minority Media Telecommunication Council) ideas for a radio rescue first bantered about in 2009.

This demonstrates that the NAB and the FCC are not at all serious about revitalizing the AM band but merely marking time and making it look good until the final transmitter is switched off.

AM licensees are on their own, but all is not lost. I have noticed several successful stand-alone AM stations that are not only surviving but thriving. The common thread in this station is good local programming. On the technical side of things; a well-maintained plant with good quality audio feeding a properly operating transmitter and antenna array will go a long way to providing good service to the city of license.

Computer guys…

Some guy posted this picture on Reddit:

In the comments, he gets blasted for being too neat and using wire ties. I know a lot of IT guys that are not very neat with their work and document nothing. This is a big problem in the industry and does not, contrary to popular belief, promote job security. I have walked into some very messy situations in wiring closets and rack rooms over the years. My solution is always the same; run some temporary wires for critical machines/functions, then get out the big wire cutters and start chopping.

Time to consult the transmitter wall

I saw this at the WIZN transmitter site in Charlotte, VT:

Somebody went through quite a bit of trouble to chart the transmitter readings from April of 1987 through about February of 1992.

A closer view:

I have not seen this at any other transmitter site, so I thought it was an interesting way to keep a transmitter log. It also seems to be time-consuming and a bit obsessive. Over the years, I have found my fellow broadcast engineers to be a somewhat strange group sometimes.

Troposcatter communication system

I found this interesting article on the inter-tubes the other day and thought that I would share it. It is about a disused site from the Soviet era Troposcatter communication system called “SEVER.” There are many more pictures of equipment including MUX, transmitters, antennas, buildings, etc, at that link.

Soviet SEVER troposcatter communications antenna, courtesy ralphmirebs.livejournal.com

Like many of its counterparts in the US, this system has quite a bit of information available, including an interesting blog and associated web site which has lots of interesting information. Some of it is in Russian, which mine is a little bit rusty, but here is what I could find out:

This is site 6/60, call sign Poloska and is located in Amderma, Nenets Autonomous okrug. That is way up north along the Barents Sea. This site was in use from about 1965 until 2001 when it was closed down. It communicated with site 5/60, which was 264 km away.

Amderma map with SEVER 6/60 location, courtesy of trrlsever.org

Troposcatter was used widely before satellites came into availability. It used decimeter wavelengths (approximately 2 GHz) and lots of power with very high gain antennas. Basically, the earth and the troposphere were used as reflectors, creating a type of duct. It is noted the SEVER and the GOREEZONT (HORIZONT) systems used both space and frequency diversity as a part of their system. Frequency diversity means that there were as many as five identical signals transmitted on different frequencies at the same time. Space diversity means that two or more transmit and receive antennas were used, as can be seen in the picture. This site was run by the military but would have likely carried civilian communications as well.

Basically, it was a way to maintain communications across vast distances when wired or microwave systems were not practical or possible. The US used such systems on the DEW line and across the Pacific Ocean between Hawaii and Okinawa. I remember the big Troposcatter dishes up on the hill behind the Navy housing area above Agana.

US Pacific Troposcatter communications system, courtesy of Wikipedia

These systems were massive and expensive to build, operate and maintain. From the looks of the pictures, site 6/60 generated all of its electricity with diesel generator sets. Fiber optic cable is an improvement of several orders of magnitude over this technology.

It is always interesting to see how things used to be done and give thanks to those that went along before us. Last night I was grumbling about the network latency when watching a youtube video. It was terrible, but in retrospect, not really that bad.