AM – Page 16 – 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.

It is kind of tragic, in a way

Working on another AM directional station (WGDJ) which was damaged by lightning recently. In this case, the antenna array controller ceased working and one of the towers in the daytime pattern was out tolerance. Before we stared working, I told the owner to have all the vegetation cut down around the towers. This is what we ended up with:

I can’t really fault them for this, but it does make work more difficult. That strip of tall green grass; that is the catwalk. The grass itself is called Phragmites, which is tall, tough, reedy stuff that can scratch and cut person unaware. The array is in a low swampy area next to the Hudson River in East Greenbush, NY. Stepping off of the catwalk, one can sometimes find solid ground, or find ones feet six inches under water.

WGDJ tower one ATU cleanout — WGDJ tower one ATU clean out

This is Mike cleaning out the mice and bees nests out of the tower #1 ATU. Notice the can of bee spray in his back pocket. This was after he was stung in the forehead.

Mouse nest, WGDJ daytime ATU coil — Mouse nest, WGDJ tower #5 daytime ATU coil

This mouse nest, at the attendant dead body in it, was responsible for a -10 degree phase shift in the daytime pattern for that tower. I hate cleaning this stuff out, it is a dirty, nasty job but necessary nonetheless. While doing this work, I wore gloves and a dust mask. The entrance hole where the AC power and control cables come into the bottom of the ATU was plugged up with some steel wool. There is still a bad capacitor in this ATU for the daytime array, that damage was likely caused by lightning.

At the end of the day, we repaired the antenna array/phasor controller; bad AC transformer and rectifier bridge and several bad logic steering diodes for tower 4 and 5, cleaned out all the vermin nests and isolated the remaining problem with the daytime antenna system. Parts should be in next week to finalize repairs.

All in all, not a bad day’s worth of work.

WKNY, Kingston, NY

This is another one of those, ahem, AM success stories. WKNY is on 1490 KHz, 1,000 Watts day and night from a transmitter site that is located very close to its target audience of Kingston. It signed on on December 16, 1939, broadcasting 100 watts on 1500 kHz according to the Broadcasting Yearbook 1940 edition.

The transmitter location is the key to this station’s good signal over Kingston. Even though it is a class C AM station when driving around the Kingston city limits there is no electrical interference or nighttime co-channel interference. The reason for this is that most of the city limits are within 2.5 to 3 miles (4 to 4.8 km) from the tower.

This is the original transmitter building and tower. Like many old AM transmitter sites, this one is located in a low, swampy area. The tower is electrically tall for 1490 KHz, at 92 meters (305 feet) it is 163 electrical degrees. Something else that may contribute to the station’s performance.

WKNY tower, a typical design of a uniform cross-section guyed tower from the late 1930s to late 1950s.

WKNY transmitter. Another Nautel ND-1 series transmitter. Nothing ever breaks or goes wrong.

The air studio has an AudioArts R-60 console. For an inexpensive audio console, these things sure seem to last for a long time. I think this one was put in in 1997.

A small talk studio is used to originate local programming of interest. This morning, I was listening to “Speak Out With Jody McTague,” a local interest program that was discussing the impacts being felt in the Kingston area due to the “Affordable Health Care Act.”

The production studio has a rather old Harris rotary pot console from the 1980’s.

Of course, all of this equipment makes radio transmission possible, but what makes radio itself is the local people working at the station and bringing relevant information to the area. I know a lot of very smart people are working on the “solution” to the AM problem. It really has to do with the programming.

Happiness is: An AM directional array at licensed values

Last week I did some repair work at WDDY in Albany NY. It seems the sample line on one of the towers was melted in half by a lightning strike. This station uses sample loops up on the tower for its directional antenna monitoring system.

As it happened, the sample line in question was on the reference tower, which makes everything else meaningless. Before the meltdown, there were several years’ worth of maintenance logs that showed the previous values for current ratio and phase relationship.

With the transmitter turned off and locked out, I removed the damaged section of the line from the base of the tower to the RF choke coil in the tuning house. Where the sample line came off of the base of the tower, there was a UHF-type connector that had been improperly applied. Using spare parts, I fixed that connector, then spliced the line into place. Upon power-up, the transmitter and antenna readings returned to their previous values, which were slightly out of tolerance.

Thus, some phasor tuning was needed. There are not too many people left that can properly tune an AM phasor. All of the control interact with each other; moving the power or phase to one tower will likely affect all of the other towers and possibly the reflected power on the transmitter. This phasor was made in the 1970s by Multronics with what looks like all RCA parts. Multronics, I think, was John Mullaney who is more known for the folded unipole antenna. In any case, after a good few hours of careful hand cranking and a run out to the reference tower to move a coil tap, here are the results:

Not bad for a day’s work.