The death of WLNO-AM

The best place to put an AM transmitter is in a swamp. It is also the worst.

WLNO-AM is located in New Orleans, Louisiana. To put out its 50,000 watt daytime, 5,000 nighttime signal required 7 antenna towers.

Here is some of radio message board Gossip. Hurricane Isaac in 2012 flooded the site leaving the buildings full of mold and asbestos. The station reverted to the bank holding the loan.

The towers were torn down, the equipment removed from the property, and the FCC has agreed to let the station run on a long wire at low power while they decide what to do. AM signals radiate outward perpendicular to the antenna, so a long wire antenna is highly directional and without a ground system, basically useless.

The new owner paid $60,000 for the license and gear like the satellite dishes, break room table and cart machines in order to run a gospel music station.

Cart machines were a little like 8 track tapes. You kept them in racks, and when you inserted a cart into the player, it would position itself to the start of the audio and automatically fire off when requested. They were used to store advertisements primarily.

My impression was they could be linked together so that when one finished, it would start the next one. Magnetic media is a problem – each time it is played, a small amount of the signal is lost. Cart Machines died about 25 years ago except stations that had no money and/or resisted technology and were happy being dinosaurs until they died.

Computers using digital media stored on hard disks don’t have that issue as long as your computer is not grabbed by ransomware because a DJ used it to surf for porn. Digital audio is 100% reproduced and can be reproduced an infinite number of times, hence the quandary the music business has.

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8 Responses to The death of WLNO-AM

  1. Parrott says:

    I had the Radio Shack ‘One-transistor’ AM transmitter kit. It ran on a 9 volt battery.
    Little crystal microphone attached to it. It worked pretty good. If you could turn up the modulation it would have been good.
    I hooked it to the long Ribbon wire from the TV antenna . It went up on the roof and a good Ten foot pole. I could pick it up almost a half a mile away with a good AM radio.
    It was a Vertical line up to the TV antenna. I wonder what that transmit pattern was ?
    The TV antenna was a cheapie, like a single boom Yagi type.
    I bet that pattern was crazy. I wonder if it went out further at night? probably not since it was so low power.
    I have that thing out in the shed somewhere

    So a AM transmitter antenna is a single aerial on top the tower?
    The FM antenna were usually four small ‘T’ sideways on the tower. Not quite at the top.
    Interesting
    parrott

    • Fred Stiening says:

      I’m not a radio engineer, but have picked up some of the concepts just doing random reading, especially trying to understand what DBm is relative to signal strength.

      For an AM station, the tower does not hold the antenna – the tower is the antenna. The RF signal is just electrically connected to the base, and the length of the tower has to match the frequency of the station. When the length of the tower is right, it starts to resonate and the RF flows outward.

      But to really be heard, an AM station also needs a second piece – the ground system of copper radials. It provides the second end of the RF waves and to a large degree is more important than the tower. Different parts of the country have better conductivity. By far, the most effective ground conductivity is through water.

      Most AM towers are bottom fed 1/4 wavelength. The lower on the dial, the taller the antenna has to be. 1/2 wave or full wave antennas are impractical and don’t add that much signal improvement.

      If the antenna is vertical, the power spreads out horizontally in a circle. It doesn’t go upwards into outer space. However, the earth is round, so as the signal travels in a straight line, it gets higher and higher above the ground and eventually hits the ionosphere which reflects the signal back toward the ground. Radios are generally built to require a -60 dbm signal to hear. That filters out the noise and limits interference from adjacent channels. Transistor radios have directional ferrite cores which allows you to steer the antenna. Cars use ominidirectional antennas since it would be annoying if stations dropped out when you go around a corner

      • Parrott says:

        Ah ‘ the whole tower’ that’s good to know.

        I remember the local radio station we toured in scouts. They had that tape cart, ( it was 1978) the AM studio was on ground level and glass windows from floor to ceiling for the studio. The DJ could see out to the field towards the tower. There was still a DJ in 1976 on AM. The sister FM station was in the basement and no live person unless someone went to read the weather report, it had that two or three of those tape carts. We watched it cycle a bit to play a commercial or two. I think the music was reel to reel on FM, I can’t remember if it was from a satellite.
        The tower was 150 feet tall, transmitted 1260 khz . You probably remember Chevrolet ( GM) use to have that AM antenna in the front windshield. It kinda acted directional.
        Our 06 Lexus has the antenna in the rear glass ,its definitely directional when driving away from the transmitter, receives good. Driving toward it at distance, radio may not find the station, till it gets close. Its pretty wild.
        thanks for the info
        parrott

        • Fred Stiening says:

          The attitude of AM toward FM was the FCC handed them a “free” companion license in the 1960s, but with the condition it could not be a simulcast. Many turned down the offer as lots of cars still had AM only. Those that got the license often did just what you described. It ran on automation and nobody much cared about it. By the 1970s, the situation started to reverse. Rush Limbaugh and Quinn were riding the end of the top 40 on AM wave around 1973

        • Fred Stiening says:

          Here is a calculator

          http://www.csgnetwork.com/freqwavelengthcalc.html

          It is possible to monkey with the height by creating artificial height, but it makes the system less efficient. But in general, you can’t just move AM stations around.

          When the towers of WMAL come down, the plan is to do what is called diplexing, which means using one tower to transmit more than one AM signal. The “how they do it” isn’t clear, but with Cumulus getting $75 million for the land, they really don’t care if they kill the AM radio station.

          http://www.radiomagonline.com/deep-dig/0005/diplexing-am-transmitters/26200

          With directional AM, there is zero margin for error – the directional pattern is based on the towers being an exact distance apart based on the frequency. For that reason, diplexjg only works on non-directional antennas

        • Fred Stiening says:

          Sign outside the WMAL transmitter site… you can see the base of one of the towers

          • Parrott says:

            I have bee looking at that coverage link to
            ‘radio-locator’ and checking out their new improved map. Some have truly directional signals. I have been listening to WBZ Boston in the Jeep if I am out after 6pm. They come in very good here, WBT has faded in the evening in the last few months.
            True the map only shows the Daytime coverage area, unless its a station that knocks their power down to 36 watts at night. Its good info.
            They will show Canadian radio stations too.
            I was looking at CMFJ Toronto and it is truly aimed north.

            So cumulust business plan is cannibalize their stations. They will be in textbooks one day with examples like Enron & MCI
            parrott

  2. Fred Stiening says:

    Rather than nesting comments deeper

    Making AM stations directional can be done a little by cutting back the radials in the direction you don’t want the signal to go, but serious directional requires putting two (or more) towers at a distance related to the wavelength – the signal is synchronized so the two signals cancel each other in one direction and double up in the other.

    The original Class A 50 kw “clear channel” stations have a 750 mile protected contour after sunset which made sense in 1928 before TV, satellites and the internet. One way to save AM radio would be to cut that back to their daytime contour and allow AM stations to run more power at night to keep the local audience around, but it is probably too late. I can see from the stats here and from other sources that people don’t listen to radio after dinner. Listening to the clock radio when falling asleep has been replaced by other things, which also means people are not waking up to radio.

    FM radio is much simpler. You can’t put an FM radiater on an AM tower because it disrupts the AM signal. You can’t even build a new FM tower close to an AM tower as it will distort the AM pattern.

    So most FM stations use a shared tower that the radio station doesn’t own and just rent space on the tower and in the building at the base. The full wavelength at 100 MHz is 9 feet – changing from 88 to 108 MHz barely changes the resonance length. My dad had a 2 meter transceiver (1970s) that normally was around 144 MHz – each Channel had a crystal and had a trimmer capacitor to trim up the antenna. The antenna was a magnetic mount on the roof with maybe 18 inches sticking up.

    All of this is now just done by computer circuits which measure the antenna in real time and adjust the transmitter. The FCC recently approved an AM technology to modulate the power of the signal based on the carrier content. There is no need to run at full power in between the words that George Noory speaks and waste the energy.

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