FM Broadcasting and FM Band DXing
(and, oh yeah, we do TV too!)

LEGAL DISCLAIMER:  We are crazy.  We spend our hard earned money on expensive receivers, antennas and other electronic junk.  We climb up on towers in the coldest of weather to make that last little tweak to our antenna in an effort to squeeze out just a little bit more signal.  We spend hours and hours listening to weak, scratchy, distorted radio signals and fuzzy TV pictures from far, far away places!  We are known as "DXers."  You have been duly warned.  We cannot be held responsible if our particular form of insanity should infect you.

Intrigued?  Then read on if you dare.

Essentially, DXing is the art of sifting and straining the airwaves for distant signals.  There are many forms of DXing, including AM broadcast band, shortwave, FM broadcast band, and even TV DXing, to name a few. Always, the goal is to pick up stations from as far away as you can.

This web site is devoted to TV and FM broadcast band DXing.  Impossible?  Not at all!  When the right conditions exist, it's entirely possible to see and hear TV and FM broadcast stations from 1,500 miles away or more!       

Still intrigued?  If so, you might be just crazy enough to hang around here and read all about this fascinating hobby!  Who knows, perhaps mysterious things like sporadic E and meteor scatter will capture your interest.  Perhaps you just want to see a picture of my really big antenna! 

If you've gotten this far, you might already posses a genetic pre-disposition toward DXing. It might already be too late to save you.  Beware, once it gets in your blood, there is no cure!  But, don't be afraid, it's usually not fatal. 

Your Host,

Girard M. Westerberg
Lexington, Kentucky

A Brief History of FM Radio

Edwin Howard Armstrong, born on December 18, 1890, is credited with being the inventor of FM radio.  At age 22, Armstrong took Lee de Forest's new invention, the electron tube, and redesigned it.  While experimenting with the new electron tube, he discovered that by feeding a portion of the tube's output signal back to its input, the circuit's ability to amplify signals was dramatically increased.  He called this phenomenon "regeneration."  This fundamental principle of electronics was the basis for early radio receiver designs in the form of the regenerative and super-regenerative models.   Armstrong also discovered, probably by accident, that if the level of regeneration was increased beyond a certain critical point, the tube would self-oscillate, producing a radio signal in the process.  Armstrong patented his discovery in 1913.

While stationed in France during World War I, Armstrong improved his radio receiver design by inventing what's known as the "super heterodyne" radio receiver.  Virtually all receivers in use today employ Armstrong's super heterodyne concept.

In the early 1920s, the airwaves were buzzing with radio signals, all amplitude modulated (AM).  By the end of 1922, the government had licensed around 550 stations across the United States, with most of these stations broadcasting with modest power levels on 360 meters, or approximately 832.8 Kilohertz.  Radio was the rage.

Armstrong wasn't satisfied with the performance of AM radio, especially its susceptibility to static, noise, and interference, as well as its poor tonal quality.  He began experimenting with what he called "Armstrong Modulation." This would later become more commonly knows as frequency modulation or more simply, FM.  Over the next decade, Armstrong further improved upon his earlier receiver designs, and continued to advance the upper end of the known radio spectrum by perfecting transmitters and receivers operating at higher and higher frequencies.

By 1934, Armstrong was ready for the first field tests of his radical new radio systems.  For these tests, he used both a conventional AM transmitter, and his new super high frequency FM transmitter.  Both transmitters were set up in the Empire State Building under the supervision of RCA engineers and executives.  The results were astounding.  The FM signal was received in Long Island with no static and excellent audio quality, while the AM signal suffered from limited audio quality, and the usual static and fading.  Armstrong had proven that his new high frequency FM broadcasting concept was not only technically feasible, but superior to AM radio in almost every way.

By 1939 there were approximately 40 high frequency FM stations on the air, mostly experimental in nature.  In May of 1940, the Federal Communications Commission  formally allocated the 42-50 megahertz band to FM radio broadcasting, and applications for the new service poured in.

Unfortunately, there were several problems with the new radio service.  Probably the principal problem was that most people were unwilling or unable to invest in the new dual-band AM/FM receivers.  Times were tough.  The United States had entered World War II, and the war effort was given priority when it came to the production of electronic components and radio equipment.  The few consumer radios that were produced during this time were so expensive that only the wealthiest individuals could afford them.  Without listeners, the new FM service was quickly proving itself to be an economic failure.

It was quickly discovered in the early days of FM radio that distant signals would often interfere with local stations, sometimes rendering the local service totally useless.  These very high frequencies were originally believed to be "line-of-sight" only, so the occasional long-distance signal propagation was seen as a considerable nuisance, especially by station owners and management.

During the early 1970s I worked as an engineer for KLZ and KLZ-FM in Denver, Colorado. While rummaging around at the KLZ transmitter site one day, I came across an old box containing correspondence between the government and the station, dating all the way back to when KLZ first came on the air in the early 1900s. Among the many utterly fascinating items in that box was a letter the station owners had written to the FCC in the early 1940s.  In that letter, the station owners, The KLZ Radio Company, were "turning in" their license for W9XLA, an early FM station operating on 25.4 MHz.  In that letter, the owners stated, "...FM broadcasting is frequently subject to objectionable interference from other FM stations and other radio signals from various places around the world."  They went on to say, "...the public has not accepted FM broadcasting, and likely never will.  We can see no future for FM broadcasting.  We are therefore respectfully turning in our license for cancellation."

The KLZ Radio Company wasn't the only FM broadcaster to take this drastic step.  During World War II, many of the early FM stations turned in their licenses and construction permits, all pretty much giving the same reasons The KLZ Radio Company gave.  It looked as if FM broadcasting's brief history would come to a premature end.

Fortunately, the concept of FM Radio apparently still had a few supporters, including some members of the FCC.  In three separate reports issued during 1945, the FCC formally allocated the 88 - 108 MHz portion of the radio spectrum for FM broadcasting, thus creating the FM band as it exists today.  They sat aside 100 channels, each 200 kilohertz wide.  Eventually, the frequencies between 88 and 92 MHz were allocated for educational and non-commercial purposes, and those between 92 and 108 MHz were allocated for commercial use.

In it's report, dated May 25, 1945, the Commission stated, "In making an allocation for FM, it is the Commission's purpose to make provision for a service which will not be simply a new and improved broadcast service but which will be the finest aural broadcast service which is attainable under the present state of the radio art.  The commission confidently expects that in the years to come this new service will develop to a point where there may be between 1,000 and 3,000 FM transmitters and between 50 million and 100 million FM receivers in the hands of the public.  In planning for such a service it is obviously of the utmost importance that the allocation be made in the portion of the spectrum which is best suited for that purpose.  With respect to allocations for other broadcast services it has sometimes been necessary to make compromises between various services competing for particular parts of the spectrum.  However, with respect to FM the Commission is prepared to assign to it that portion of the spectrum which is shown to be best suited to its requirements.  The Commission feels that it must proceed on this basis because it seems clear that this important new broadcast service will remain permanently in the portion of the spectrum to which it is assigned as a result of this hearing."

The passage of time has proven the wisdom and foresight of the FCC's deliberations during 1945.  However, FM radio's future was by no means secure. By the end of the 1940s, there were relatively few FM stations operating across the United States.  Broadcasters, having already been burnt once by a new technology the public ultimately didn't accept, were reluctant to throw their financial support into yet another new and unproven service.  The few FM stations that did exist usually ended up simulcasting the programming of their sister AM stations.  AM was still king, and would remain so for many years to come. 

It wasn't until June 1, 1961 that FM stereo broadcasting was authorized by the FCC.  The first stations to notify the FCC of regular stereo operation were WEFM in Chicago, Illinois; and WGFM in Schenectady, New York.  Finally, FM radio could do something AM couldn't: deliver high quality stereophonic programming to the listening public.  This, perhaps, was the turning point for FM. 

During the early 1960s FM radio was dominated by classical or "beautiful" music stations.  Many people believed that FM stood for Fine Music.  I encountered more than one person that thought that it was somehow against the law to play anything else on FM radio.  The more popular Top-40 and country music radio formats were still confined to the AM broadcast band.  AM radio continued to dominate in terms of audience popularity, ratings, and advertising revenues.

Then in the mid 1960s something of an FM Radio revolution took place.  More and more FM stations were abandoning their "fine music" formats and AM simulcasts.  They started trying out more mainstream formats.  As the decade of the '60s continued, youth unrest surrounding the United States' involvement in the Viet Nam war grew.  From that unrest sprung the Progressive and Album Oriented Rock formats.  These formats proved to be hugely popular, and were confined almost exclusively to the FM band.  For the first time in radio's history, a whole generation grew up listening almost exclusively to FM radio.  By the early 1970s it was becoming more common for AM stations to simulcast the programming of their more dominant FM sister stations.  The pendulum had finally swung fully in the direction of FM radio where it remains to this day.   

Early DXing

Pushing the limits has always been a dominate characteristic of human nature.  When the automobile was invented, it didn't take very long before someone wanted to know just how fast or how far the automobile could go.  When airplanes were invented there were those who wanted to know how high the airplane could fly.  Why should our attitudes be any different toward the invention of radio?

Early radio pioneers immediately set out to push the limits of their new inventions.  It was a world-wide news event when the first radio signals were successfully sent across the Atlantic Ocean on Thursday, December 12, 1901, by Guglielmo Marconi.

As commercial AM broadcasting became popular in the 1920s, it was only natural that the listening public would also want to get in on the act of pushing the limits.  Many radio enthusiasts endeavored to hear and log as many stations as they could, trying all the time to hear stations from greater and greater distances.  Radio DXing quickly became a popular pastime.

A portion of Bill Smyth's 1939 radio log
An excerpt from Bill Smyth's (Denver, CO) 1939 radio AM log.  Bill was in the tenth grade. 

Perhaps the first published report of an FM DX reception appeared in the February 1942 issue of FM Magazine"Zenith Radio Corporation, operating W51C [45.1 MHz, Chicago], has received a letter from a listener in Monterey, Mexico, telling of daily reception of this station between 3:00 P. M. and 6:00 P. M. This is the greatest distance, 1,100 airline miles, from which consistent reception of the 50 KW. transmitter has been reported."

While DXers were thrilled by the long distance signal receptions they were increasingly hearing on the new FM band, everyone else associated with the business of FM broadcasting was disappointed and frustrated.  Unlike the old AM band, the new FM radio service was supposed to be free from interference, yet the interference from distant signals seemed to be increasing.  What went wrong?

In 1939 when the original group of FM frequencies was allocated, the eleven-year solar sunspot cycle was at a relatively "quiet" point.  Radio engineers already had a fairly good understanding of how the sunspot cycle affected lower frequency transmissions, especially at frequencies below 30 MHz.  They understood that as one went higher in frequency, a critical frequency would ultimately be reached where the upper layers of the ionosphere (the F layers) would no longer support long distance signal propagation.  They also understood that as the sunspot numbers increased during the eleven-year solar cycle, the critical cutoff frequency for long distance transmission also increased.  However, up to this point there had been little opportunity to study the effects that solar activity had on VHF frequencies.  In addition, so called "tropospheric" signal effects were complicating station coverage predictions and signal propagation studies.  Sporadic E, a phenomena that makes long distance VHF signal propagation possible, had just been discovered by amateur radio operators a few years earlier, and serious study was just beginning.  Strange "bursts" of distant VHF radio signals were noticed and recorded, but it would be several years before it would be discovered that meteors entering the atmosphere were the cause. The new FM band was clearly a mess for everybody except the FM DXer!

The task of "fixing" the problem rested squarely on the shoulders of the relatively new FCC.

In 1945, the National Bureau of Standards predicted that by April of 1946 the ionosphere would be capable of supporting F2 transmission of frequencies between 44 and 56 MHz for 50 percent of the time during mid-day hours.  The problem would only get worse as the sunspot cycle was predicted to peak during the summer of 1947 (and peak it did, with sunspot numbers briefly exceeding 200).  In a sense, the FCC was trying to beat the clock, anticipating what they termed "...the disastrous effects anticipated from F2 interference" when they decided to move the FM band.  According to early FCC documents from 1945 and 1946, "The three major factors which the Commission considered in its decision to place FM in the 88-108 megacycle band were (1) sporadic E interference, (2) F2 layer interference, and (3) extent of coverage."

FM DXing - Life would be terribly dull for the FM DXer had the FCC of 1945 been absolutely correct in its belief that the 88-108 MHz portion of the radio spectrum was the best place for the new FM broadcast band. Given their stated goal of protecting the new service from the ravages of sporadic E and F2 layer interference, the FCC was NOT totally successful.  The FM band has indeed proven itself to be immune to F2 layer interference (so far). However, to avoid the effects of sporadic E, they probably should have positioned the new FM band somewhere between 250 and 300 MHz.  It's fortunate for FM band DXers that they didn't!

From the DXer's perspective, the frequencies of the FM band are full of opportunity.  At different times of the year, we can enjoy almost every form of signal propagation known to exist.  FM signals sometimes get "ducted" over great distances by various weather phenomena.  Signals sometimes bounce off of highly ionized patches in the ionosphere known as sporadic E clouds, enabling reception of signals from 1,500 miles and sometimes beyond.  FM signals even bounce off the ionized trails left behind by meteors as they burn up in the atmosphere.  The aurora borealis, or northern lights as they are more commonly known, sometimes reflect FM signals, enabling long distance FM reception.

New modes of VHF signal propagation are still being discovered, and a great deal of study is currently in progress.  Most recently, the Field Aligned Irregularity (FAI) theory of VHF signal propagation (offshoot of sporadic E) has been advanced. 

Many old mysteries still remain.  We know how Sporadic E affects VHF radio signals.  However, after over sixty years of intense study, we still don't know exactly why these strange clouds of ionized particles form.

I don't want to scare you away.  You really don't have to be a scientist to enjoy FM DXing.  However, it does help to have a decent working knowledge of the various "modes" of signal propagation if you want to capture the best FM DX.  That's why I'll go into a little more detail in the "Signal Propagation" section.