More than an aeronautical landmark

Flying VFR in New York City’s Hudson River Corridor, you’re now required to report abeam “Alpine Tower,” a longtime FAA visual reporting point. I was recently reminded of the radio pioneer behind that tower. Don’t know Edwin H. Armstrong? Know why there is no Channel 1 on your TV set? Know why you can listen to radio without headphones?

Alpine Tower is distinctive with its three 150-foot crossbeams on a squat 400-foot tower topping out at 925 MSL. As a “Jersey Boy,” I prided myself knowing the name derives from its location in Alpine, New Jersey, on the Hudson’s west bank north of the George Washington Bridge.

Photo by Susan Conova

Photo by Susan Conova

Turns out, Alpine Tower was the start of commercial FM broadcasting, a technology Armstrong (a mostly forgotten radio pioneer) invented. The tower also symbolizes the tragedy of Armstrong’s life filled with patent suits and a frequency spectrum battle nastier than LightSquared vs. GPS.

You know the story if you read Tom Lewis’ 1991 Empire of the Air (or saw the 1992 Ken Burns PBS documentary.) RCA’s David Sarnoff asked radio genius Edwin Armstrong to eliminate static from AM (amplitude modulation) radio, which dominated American broadcasting before TV. Instead of developing “a little black box” to fix AM, Armstrong invented frequency modulation (FM) — an entirely new transmission method. Sarnoff feared it would obsolete his AM empire. Besides, RCA was developing commercial television. Who wanted better radio?

Armstrong was quickly kicked out of RCA’s experimental lab in the Empire State Building. He soldiered on at Columbia University and at the FM transmitter he self-financed and built at Alpine in 1938. In 1940, the FCC authorized FM broadcasting in the 42-54 mHz band that was to have been TV Channel 1. (Now you know.)

Modulating frequency, rather than amplitude (signal strength), FM was superior to AM. It could reproduce almost the entire frequency range of human hearing. For the first time, broadcast music was realistic to the ear. There was no static from bursts of electrical energy, as from lightning. And FM stations could transmit farther or use lower power and they didn’t interfere with each other. Only the strongest FM signal was heard, not multiple stations simultaneously.

FM signals penetrated the ionosphere rather than bouncing back to earth creating nighttime interference a thousand miles away. “Skip distance” no longer required power reductions or station shut-downs after sundown. (FM’s ionosphere penetration later enabled radio communications with spacecraft.)

Armstrong’s W2XMN (later WFMN) began transmitting from Alpine Tower in 1941 on 42.8 mHz. It could be heard loud and clear 100 miles away at the tip of Long Island. The innovator next put FM on radio’s Yankee Network throughout New England using inexpensive FM-based relays to local stations. The industry fought back. AT&T, for instance, wanted to protect its role in distribution of network radio by land line.

The big blow, however, was the old bugaboo of frequency (spectrum) allocation. In 1945, RCA got the FCC to move FM broadcasting to today’s 88-108 mHz band — justified, in part, by the supposed threat of the 1948-49 sunspot season. So by FCC fiat, a half-million new FM radios were obsolete. I first learned of this as a kid, discovering a discarded FM radio with “wrong” dial numbers in my aunt’s attic.

Police radio took over FM’s original frequencies (putting an end to listening in on local cops with your living room set.) But the big impact was on FM broadcasting, setting back its growth a decade or more. Most broadcasters could not afford to re-equip stations so soon after their initial investment. FM did not achieve aggregate industry profitability until 1975, and then only after the introduction of FM stereo.

The impact on Armstrong was far worse. After decades fighting patent suits, Armstrong took his life in January 1954. On March 31 that year, WFMN was switched off.

But Alpine Tower is still in use today, and played a key role after 9/11 when transmitters atop the World Trade Center tumbled. A week later, New Yorkers got back five of their TV stations from back-ups on Alpine Tower.

Edwin H. Armstrong invented key basic technologies making modern radio and TV possible. Their technical names, some derived from Greek, can be tough to grasp today. We take it all for granted. But Armstrong’s regenerative circuit (1912) amplified radio reception so it could be heard through loudspeakers, not just headphones. His super-heterodyne circuit (1918) made home receivers both affordable and user-friendly in the 1920s. Heck, even the sound on broadcast television is transmitted via FM, invented by Armstrong in 1933. And for that he wasn’t paid a dime in his lifetime.

Perhaps all that flyers have to remember Armstrong is Alpine Tower. Give him a shout-out as you transit or sightsee along The Corridor. But first, report “Alpine Tower” with your type, altitude and direction of flight on 123.05.

 Top photo by David Brenner

© 2013 Drew Steketee All Rights Reserved


  1. ruko says

    The advantage of Armstrong’s regenerative circuit did not concern loudspeaker use. His circuit’s claim to fame was very high sensitivity. This was something that was lacking in radios of the day.

    All major broadcast TV stations in the US broadcast picture and sound using digital now. Before all the stations went to digital the picture information was transmitted using AM and the sound was Armstrong’s FM.

    Super heterodyne radios were definitely more user friendly but not more affordable. There are many more parts to a super heterodyne. A big advantage of a super heterodyne is selectivity. The regenerative radio is highly sensitive but not very selective. It had a hard time separating stations transmitting on close frequencies. For example if you wanted to listen to a weak station and there was a stronger station nearby on a different frequency the stronger station may ride in and interfere. With a super heterodyne this problem is greatly reduced. Regens are still being used in applications like garage door opener receivers.

    • Drew Steketee says

      Thanks, Ruko…
      I am less than an amateur at radio, but now can enjoy learning more about it in retirement. Clearly, you know a lot. Thanks. After I filed the story, I said to myself, “Damn, I’ll bet TV audio is digital now, too!” Too late….

      On “affordability,” my point was this: While the new receivers of the 1920s were certainly more expensive than “crystal sets,” their simple, user-friendly tuning helped make them hugely popular (along with the advent of broadcast programing.) The vast volume of sets produced helped in their affordability (the parts count of the American “5-tube” receiver aside.)

      • ruko says

        Correct about the “5-tube” radio. So many were produced the cost came down. It took 5 tubes to make the average run of the mill superhet but only two tubes to make the average regen. Of course there were variations in both making them more complicated. My first ham radio receiver had 9 tubes. An RF stage, two conversion stages, three intermediate frequency stages, a detector stage and two audio stages. Man do I miss “tubes”. When it was cold in the ham shack you just turned on the radios and soon the warm filament glow made the room very cozy.

  2. Ken Deken says

    Interesting combination of radio and aviation, two areas that fascinate me! Even though I have a simple amateur radio license and have followed radio for years, I never knew the story of channel 1. I remember when my Dad first brought home an FM radio in 1960. I wondered “how is this different from the radio we already have?” Also interesting to me is that aviation continues with AM due to the fact that weaker stations can be heard, rather than the selectivity of the most powerful station only on FM. Thanks for the article.

  3. says

    Drew, you wrote:

    “FM signals penetrated the ionosphere rather than bouncing back to earth creating nighttime interference a thousand miles away. “Skip distance” no longer required power reductions or station shut-downs after sundown. (FM’s ionosphere penetration later enabled radio communications with spacecraft.)”

    Those advantages, though real and significant, are attributable to the frequency allocation of the FM broadcast band, and are in no way a function of the modulation mode employed. The 108-138 Mhz VHF aeronautical band (which is mmediately adjacent to the current FM broadcast band) is now ised for VOR, Localizer, Glideslope, and ATC Comm. It enjoys the same immunity to ionospheric propagation which you describe – and those applications employ AM!

    Safe skies,

    • ruko says

      Dr. H

      I realize AM is used for these aeronautical applications but I’m wondering why frequency modulation isn’t used? FM receivers are far less affected by noise and atmospheric disturbances like lightning, etc. There must be a good reason we are staying with AM, I just don’t know what that might be. Maybe it’s because it has been used for so long, why change. Next will be digital I fear.

  4. Douglas Drummond says

    I have been in electronics much long that I have been an aviator, so I knew about the Regen Receiver, I had two such Knightkit short wave radios. I knew but had forgotten about the superhet design, at least that Armstrong invented it. My grandfather had an old radio with the “Channel 1” FM frequencies. This is a fascinating story.

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