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What is the most crowded FM frequency?

I recently purchased the latest edition of the AM Pattern Book (as you have heard me promote before), and went thru the pages, counting the stations on each frequency, and what type of channel it is.
Wow! An interesting way to kill a couple of hours.
5125 AM MW Stations in North America....58 Clear, 54 Regional, and 6 Local frequencies.
1079 stations on the 6 "Locals".
 
Man oh man! 5125?! And I've only got 603. I'll be going to age 90 trying to get 5,000...

-crainbebo
 
Schroedingers Cat said:
Electromagnetic (EM or TEM) waves of all types have a polarization in a single plane. If you draw a sine function representing a wave, the plane of the polarization is the plane of the paper you draw it on. This can be electrical or magnetic, and in all EM waves, these are perpendicular to each other. FM Broadcast Band (and all other wavelengths) antennas, both transmitting and receiving, have a physical orientation which normally is the same as the electrical component of the EM wave. There are also magnetic dipole antennas. Mixed polarization can be produced by separate horizontal and vertical antennas, or an oddly twisted antenna designed to approximate circular polarization. There is also a CW and CCW sense to the circular polarization, depending on whether the vertical component lags or leads the horizontal component by 90 degrees. This can be done by phasing separate antennas, or from the sense of the twisting of the antenna, CW or CCW.


There's a lot more to it than this, but this is about as simple and explanation as you can do and cover most aspects of polarization. Light waves are also EM/TEM waves. When circularly polarized light waves hit a horizontal reflecting surface at the correct angle, only the horizontally polarized component is reflected. Polarized sunglasses cut out this polarization orientation, resulting in reduced reflection and glare.

The separate H and V ERP represent the relative AMPLITUDE or height of an EM wave of each polarization. The amplitude of the wave is proportional to the SQUARE ROOT of the ERP. For example if a station is 100 kW H and 25 kW V, the V amplitude would be half of the H amplitude. SQRT 25/SQRT 100=5/10=1/2, or ONE HALF. If H and V ERP are the same the H and V amplitudes are the same. For example, SQRT 50/SQRT 50=1.

Sorry if this is confusing, but it takes a little Sheldon and Leonard language to explain it.
Click to expand...

The amplitude thing makes sense. So its always SQRT of vertical over SQRT of horizontal? What unit of measurement does the quotient represent? (In your example, would the 50/50 quotient detonate 1 foot of amplitude?)
 
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DavidEduardo said:


Current Graveyard count

1230 162
1240 156
1340 166
1400 171
1450 177
1490 181

I think what favors the higher channels is the lesser coverage of the higher frequencies, making it possible to place stations closer together.
Click to expand...

Thanks, David....

I was right about 1490, but I was sure wrong about 1230! Actually, I had thought about the lesser coverage of the higher frequencies, but I didn't think the differential between 1230 and 1490 would have been all that great on the upper end of the dial. (as opposed to, lets say between 540, and 800). It also seems being adjacent to one of the former "clear' channels didn't count for much....with 1450 being within a whisker of 1490 in terms of "population".

And, speaking of whiskers (as in crystal radios), I lived for two years as a kid in the western suburbs of Chicago, and yes, I had a crystal radio. No matter what I did with it, or how much I fiddled with it, it got exactly only one station....WCFL! (Now WMVP).
 
fordranger797 said:
The amplitude thing makes sense. So its always SQRT of vertical over SQRT of horizontal? What unit of measurement does the quotient represent? (In your example, would the 50/50 quotient detonate 1 foot of amplitude?)
Click to expand...

Since the H and V ERPs are not the same, this is actually called ELLIPTICAL POLARIZATION, not CIRCULAR POLARIZATION. Wave amplitude is a Physical Concept. Since the numerator and denominator have the same units, it has no unit. It depends on what you measure. It could be Volts to the transmitting antenna or from the receiving antenna, Amperes in the transmitting antenna or receiving antenna, or a measured field in Volts/Meter. All of these would be linearly proportional to the SQRT of the ERP, or to the Electromagnetic Field Strength in Volts/Meter (Volts per Meter) or other proportional unit like millivolts/meter or microvolts/meter. All of those would be examples of a measured amplitude of the wave. You can directly measure WAVELENGTH, but not AMPLITUDE of a wave. You have to infer it from these other measurements.

Although the H ERP could be less than the V ERP, with stations in the 92-108 region in the FM Broadcast Band H ERP has to be more than V ERP according to rules in CFR 47 Part 73. H ERP could be much less than V ERP for an NCE-FM station in the 87.9 to 91.9 portion of the band.
 
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Schroedingers Cat said:
Since the H and V ERPs are not the same, this is actually called ELLIPTICAL POLARIZATION, not CIRCULAR POLARIZATION. Wave amplitude is a Physical Concept. Since the numerator and denominator have the same units, it has no unit. It depends on what you measure. It could be Volts to the transmitting antenna or from the receiving antenna, Amperes in the transmitting antenna or receiving antenna, or a measured field in Volts/Meter. All of these would be linearly proportional to the SQRT of the ERP, or to the Electromagnetic Field Strength in Volts/Meter (Volts per Meter) or other proportional unit like millivolts/meter or microvolts/meter. All of those would be examples of a measured amplitude of the wave. You can directly measure WAVELENGTH, but not AMPLITUDE of a wave. You have to infer it from these other measurements.

Although the H ERP could be less than the V ERP, with stations in the 92-108 region in the FM Broadcast Band H ERP has to be more than V ERP according to rules in CFR 47 Part 73. H ERP could be much less than V ERP for an NCE-FM station in the 87.9 to 91.9 portion of the band.
Click to expand...

Thanks for the information; I appreciate it. So effectively, a radio signal would look like an "x" if it were visible, as there is a vertical and horizontal plane? Will a radio station have a vertically oriented transmitting antenna and a horizontally oriented antenna to accomplish this?
 
Here is one representation of the electric and magnetic components of an EM/TEM wave.

Wish I knew how to post the link so it would appear as just a picture.

http://micro.magnet.fsu.edu/primer/java/electromagnetic/electromagneticjavafigure1.jpg

The way the picture appears, this would be a HORIZONTALLY POLARIZED WAVE, because the electric sine wave displacement appears to be horizontal. This would probably come from a horizontally polarized dipole, one that is parallel to the ground.
 
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K6JHU said:
But then there is no guarantee that I didn't do the list at 2:30 either :)

Correct answer for 106.3 is 111.

BTW, the data is for 2010-2011. I suspect all that has changed since then is infilling (e.g. LPFM and Translators).
Click to expand...

Haha. I knew something wasn't right. Then again, thought maybe my eyes were playing tricks on me. :)
 
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