More news talk migrates to the FM band

Once a bastion of the AM dial, News and or News/Talk format radio stations seem to be springing up on the FM band more and more often.  The original premise for creating talk radio on the AM band was the lower bandwidth and reduced (or perception of reduced) fidelity when compared to the FM band lent itself to non-music programming.  The reality is that receiver manufactures never carried through on the NRSC-2 technical improvements, and AM receivers reproduced thin, low quality audio.  I digress, the story goes, the FM band was great for music and the AM band did well with information and talk.

Of course, there were always a few exceptions to those general rules, but for the most part, that pattern held true until about 2009 or 10.  That is when AM station’s programming began to be simulcast again (everything old is new again) on FM stations and HD-2 subchannels.   It would be interesting to examine why this is so and what it means to the radio business as a whole.

The general trend in the music industry has also been down.  This is important because record labels and the radio business used to go hand in hand.  Record labels had the job of separating the wheat from the chaff.  Those groups or artist that had the talent would be given recording contracts and airplay.  With exposure, they would become more known, sell more recordings, record more songs, etc until they peaked and began to decline.  Radio stations prospered under this arrangement because they took on none of the risk while getting huge vast quantities of program material to playback, and charge advertising fees for spaces within that programming.

So far so good.

Then, two things happened:

  1. The communications act of 1996
  2. The internet

The communications act of 1996 forever changed the way the radio business was run in this country.  No longer were there several thousand individual stations, the most influential of which resided in markets #1 and #2.  Instead there were conglomerations of stations run out of Atlanta, Fort Worth and a dozen or so other medium sized cities.  No longer were stations competing head to head and trying to be the best and serve their respective audiences; rather, station A was positioned against station B to erode some of it’s audience so that station C could get better national buys from big ad agencies.  No longer would possible controversial artists like the Indigo Girls get airplay on some groups.  Songs were sanitized against possible FCC indecency sanctions, morning shows became bland and safe, and radio on the whole became a lot less edgy as big corporate attorneys put the clamps on anything that would invite unwanted exposure.

The last great musical genre was the Grunge/Seattle Sound of the early 1990’s.  Those bands somehow mixed heavy metal, obscure mumbled lyrics, flannel shirts and ripped jeans into something that the dissatisfied Gen Xers could understand and appreciate.  By 1996, this had morphed into “Modern Rock,” and carried on for several years after that, to fade out in the early 00’s.  Since that time, there has been no great musical innovations, at least on the creative side, other than the ubiquitous Apple computer and Pro Sound Tools software.

The internet greatly changed the way recording labels did business, mainly by eating into their bottom line.  This had the effect of circling the wagons and throwing up a protective barrier against almost all innovation.  The net result was fewer and fewer talented artists being able to record, which pushed those people into smaller, sometimes home based recording studios.  While those studios can put out good or sometimes even excellent material, often the recordings lack the professional touches that a highly trained recording engineer can add.  Add to this the mass input of the internet and no longer are bands or artists pre-screened.  Some may point to that as a good development with more variety available for the average person.  Perhaps, but the average person does not have time to go through and find good music to download from the iTunes store.  Thus, a break developed in the method of getting good, talented artists needed exposure.  Youtube has become one of the places to find new music, but it is still a chore to wade through all the selections.

Thus, when FM HD-2 channels came into being, there was little new programming to be put into play.  HD radio was left to broadcast existing material with reduced coverage and quality than that of analog FM.  That trend continues today where now analog FM channels are being used to broadcast the news/talk programming that used to reign on AM.

What will happen next?  If Tim Westergren has any say, the internet (namely Pandora) will take over and terrestrial radio will cease to exist.  Current trends point solidly in that direction, although I think Tim is a little ahead himself in his prediction.

News/Talk on the FM dial point not to an attempt to shift the wheezing, white, (C)onservative/(R)epublican programming to a younger demographic, who will, if I am any judge of history, remain unimpressed.  No, rather, they are running out of other source material, simulcasting syndicated talk radio is cheap, lean and a good way to make money without having to pay actual salaries.

FM Stereo vs station coverage

There are a few FM stations around here that intentionally broadcast in mono.  One is an FM talker, which from a technical standpoint makes a certain amount of sense since any particular human voice is a single point sound generator.

The other FM station broadcasting in mono, WKZE,  has a music format with a very eclectic play list.  It is a full Class A located in north western Connecticut.  The idea with this station is to garner a larger and more reliable coverage area.

It comes down to a simple physics discussion about free space loss.  The basic equation for free space power loss is:

where:

That formula works for a single frequency, say the carrier frequency, for example. As the signal gets spread out by modulation, the power density on any given frequency is reduced as the energy is divided between many other frequencies.

First, free space loss takes into account the spreading out of electromagnetic energy in free space is determined by the inverse square law, i.e.

\ S = P_t \frac{1}{4 \pi d^2}

where:

  • \ S is the power per unit area or power spatial density (in watts per metre-squared) at distance \ d,
  • \ P_t is the total power transmitted (in watts).

Second, with Frequency Modulation (FM), the power spectral density is a function of the differences in the highest and lowest frequency:

 P=\int_{F_1}^{F_2}\,S(f)\,d f + \int_{-F_2}^{-F_1}\,S(f)\,df.

Therefore, the narrower the bandwidth of a signal, the higher the density of the received signal will be in relation to the transmitted power.  An unmodulated FM signal will have a better, more reliable coverage area than a modulated one.  Of course, we need to modulate the signal, otherwise there is no point in having the transmitter on.

A baseband or composite FM signal has several components:

FM baseband signal
FM baseband signal

An FM station transmitting a mono signal will have a much lower bandwidth. With wideband FM, the modulation index is generally 2 or two times the maximum audio input frequency. Thus, a mono FM broadcast station will have an approximate deviation of approximately 30 kHz (plus any ancillary services like RDS) vs a stereo FM station, which has a 75-80 kHz deviation using the same carrier power.

For higher power FM stations, FCC Class C and B, this is not much of an issue.  Those stations tend to have a great deal headroom when it comes to power density, building penetration, multipath (picket fencing and capture effect).  For Class A and LPFM stations, it is a different situation.  For those stations,  unless FM stereo broadcasting is truly needed, it should be turned off.  On low power stations, stereo can be a great detriment to reliable coverage.

Hot Elbow

Found this 3 inch rigid elbow to be a little warm when we were removing a dividing wall as a part of an AC upgrade:

MYAT 3 inch elbow
MYAT 3 inch elbow

As measured with my Fluke 62 mini IR thermometer, the temperature is 163°F (72.7°C) at the clamp and drops down in both directions.

This is at WEBE and this particular section of transmission line is running 34 KW into the analog/digital combiner in the next room.  The clamps are tight, but you can see a little scorch mark on the stainless steel clamp right over the slot in the field flange.  That is where there is a gap between the outer conductors, which possibly means the inner conductor was cut slightly too long during installation.  I suspect this and or a problem with the bullet is causing the heating issue.  I was never (and still am not) a fan of those field flange type elbows, I’d much prefer the flanged type with a field flange on the straight line section.

34 KW is getting into the semi-serious power level for FM broadcasting.  At those levels, even small impedance mismatches can lead to big problems.  We have a new elbow, field flanges, bullets on order.  Unfortunately, we will have to take the station off the air to replace this.

WEBE transmitter site with partition removed
WEBE transmitter site with partition removed

This is all a part of an air conditioning project. There was a plywood partition wall between the front and the back of the transmitters which was impeding air flow.  All of the HVAC contractors who bid on the AC job identified it as an problem which needed to be addressed before the big 5 ton wall mount AC units were installed.

Update: Replaced elbow last night (8/4).  Went off at 10pm and back on at 10:25.  Found the inner conductor had been pushed out of place and was off center on the outside (toward the wall side) of the elbow.  This was an older elbow that did not have the nylon inner spacers on the center conductor.  The inner conductor was dark purple.  Before replacement, the elbow was 138°F (59°C) under full power (34 KW).  After replacement, it was 97°F (36°C) as was the rest of the transmission line.  At these power levels and frequencies, even small, minor imperfections cause impedance shifts and become issues.

Myat 3 1/8 inch elbow
Myat 3 1/8 inch elbow

I cleaned up and reused the bullets and the outer conductor with scotch brite. I also used more support wires because I believe the elbow was starting to pull apart, which can sort of be seen in the first picture.