5 ms·

its more interesting that FM stations have channel numbers, which are basically not used by anyone except the FCC.

by Aloha 7y ago

taneq 7y ago
Same with analog TV stations, I never understood why they use specific ones. Why channel 7, 9 and 10 but not 8 or 6?
- drmpeg 7y ago
  All the channel numbers are used. But in the analog days, channels were separated by market to reduce interference. One market would use 2, 4, 5 and 7 while the adjacent market would use 3, 6 and 8.
- yftsui 7y ago
  Yeah its interesting why they are not widely used. Analog broadcast channels do have 6 or 8 though, https://en.wikipedia.org/wiki/Television_channel_frequencies#Americas_(most_countries),_South_Korea,_Taiwan_and_the_Philippines https://en.wikipedia.org/wiki/Television_channel_frequencies...
- Aloha 7y ago
  some places use channels 8 or 6. it just depends how many TV stations your market has
- deleted 7y ago
  [deleted]
- anyfoo 7y ago
  By the way, in Europe, even for analog TV the channel numbers have been relatively hidden since at least the 80s. TVs would instead be "programmed" to have sequential program numbers, which behind the scenes pointed to actual channel numbers. The channel a station was on could differ widely between regions, so the channel number was just a local implementation detail. There is/was also usually some more or less common order of stations, e.g. in Germany you'd always put ARD on 1, ZDF on 2, the regional "third" station on 3...
  - kd5bjo 7y ago
    For a long time in the US (maybe still?), the vast majority of the schedule was set by the local station. Being a member of one of the national networks brought access to a catalog of shows, and a few requirements about the scheduling of shows that the network really cared about. In almost every nationally-produced promo you got the phrase “check your local listings” in addition to the advertised time because the local station might air the show sometime other than when the network recommended.
- ztetranz 7y ago
  In Australia they have (or least used to have) channel zero. For many years "channel oh" was the Ten Network in Brisbane.
- dbcurtis 7y ago
  It has to do with how to hit a consumer price point with a receiver for a complex modulation scheme using only a couple dozen active devices and cheap-to-manufacture filters. Original NTSC monochrome television is a 6 MHz wide channel, the video carrier is 1.25 MHz up from the bottom, and at the transmitter a filter lops off most of the lower sideband. For receivers, the problem is the IF filter. Filters with steep skirts are hard to build and align, and are expensive. So... channel allocation was done with the assumption that most consumers would have receiving sets with poor adjacent-channel rejection because of using cheap filters. This was solved by channel allocation -- do not let two stations with overlapping grade-A signal contours be on adjacent channels. Problem solved. In the very early days in the US, channel 1 was 48-54 MHz. They found out that the percentage bandwidth was too wide to be able to build a practical transmitting antenna for channel 1. The SWR was too high at the band edges, and high SWR on analog TV means the transmission line generates ghost pictures. So channel 1 was dropped. Now hams have the 6 meter 50-54 MHz band, and cheap license-free R/C toys and walkie-talkies have 48-50 MHz. Channel 2 is 54-60, 3: 60-66, 4: 66-72 and then a gap: 72-74 is radio control, then channel 5 is 74-80, and so forth, and if I recall correctly there is a big gap between channels 7 and 8 so even though they are sequential numbers they are not frequency-adjacent channels. (7 and below being the so-called "low VHF" and 8-13 the "high VHF" TV channels.) The 2 MHz gap between channels 4 and 5 was also used to advantage, as it was enough to eliminate the adjacent-channel interference problem on reception. I recall when I lived in Minneapolis, that channels 2, 4, and 5 were all allocated in the metro area. Channel 3 was Mankato, far enough away that if you lived between Minneapolis and Mankato you could receive all of those stations without interference problems, being in the grade-B signal contour of both. And..... this entire post contains obsolete information of historical interest only, and even at that, of interest to very few. Now... excuse me because I have to readjust the spark gap on my 200 meter transmitter...
  - ThinkingGuy 7y ago
    The US Department of Commerce publishes a wall chart showing how the difference parts of the spectrum are allocated to different services. Notice how bands for "Broadcasting (Television)" are broken up and interspersed with those for other services such as aeronautical navigation and FM radio, despite the TV channels having consecutive numbers: https://www.ntia.doc.gov/files/ntia/publications/january_2016_spectrum_wall_chart.pdf https://www.ntia.doc.gov/files/ntia/publications/january_201...
ac29 7y ago
I've lived in the US for many decades and work in commercial radio, and this is the first I've heard of there being channel numbers for analog broadcast FM radio (as opposed to frequencies). I have seen channel numbers or designators like "Blue Dot" sneak into infrequent parlance in lieu of frequencies assigned by the FCC in other bands. But, this is increasingly uncommon, or in the latter case, based on manufacturer specific use. Not terribly surprised though, Title 47 is crusty and full of surprises - these channel numbers are certainly defined somewhere.
- drmpeg 7y ago
  It's funny that nobody has ever changed the frequency units from Mc/s to MHz. https://www.law.cornell.edu/cfr/text/47/73.201 https://www.law.cornell.edu/cfr/text/47/73.201
  - ac29 7y ago
    Ha, it had to be somewhere. The last I recall hearing "megacycles" was in Bond movies from the 1960s. Wikipedia says this was 1960: https://en.wikipedia.org/wiki/Hertz#History https://en.wikipedia.org/wiki/Hertz#History You can see why I say Title 47 is crusty.
    - ztetranz 7y ago
      Lots of old hams say "kay cees" and almost get offended when a newcomer says kilohertz.
- reaperducer 7y ago
  I've lived in the US for many decades and work in commercial radio, and this is the first I've heard of there being channel numbers for analog broadcast FM radio Then the station you work for must not have any repeaters or translators. When you hear a legal ID like "KHNH/Randoville, K226AR/Hacktown," the translator it got its call sign because it's on channel 226. All of the AM frequencies have channel numbers, too. I worked in radio for ten years, and wasn't even on the technical side, and I knew this.
saagarjha 7y ago
I’m curious why they start at 200.
- Aloha 7y ago
  There used to be another FM band around 6 meters

its more interesting that FM stations have channel numbers, which are basically not used by anyone except the FCC.

by Aloha 7y ago

its more interesting that FM stations have channel numbers, which are basically not used by anyone except the FCC.

taneq 7y ago

Same with analog TV stations, I never understood why they use specific ones. Why channel 7, 9 and 10 but not 8 or 6?

drmpeg 7y ago
All the channel numbers are used. But in the analog days, channels were separated by market to reduce interference. One market would use 2, 4, 5 and 7 while the adjacent market would use 3, 6 and 8.
yftsui 7y ago
Yeah its interesting why they are not widely used. Analog broadcast channels do have 6 or 8 though, https://en.wikipedia.org/wiki/Television_channel_frequencies#Americas_(most_countries),_South_Korea,_Taiwan_and_the_Philippines https://en.wikipedia.org/wiki/Television_channel_frequencies...
Aloha 7y ago
some places use channels 8 or 6. it just depends how many TV stations your market has
deleted 7y ago
[deleted]
anyfoo 7y ago
By the way, in Europe, even for analog TV the channel numbers have been relatively hidden since at least the 80s. TVs would instead be "programmed" to have sequential program numbers, which behind the scenes pointed to actual channel numbers. The channel a station was on could differ widely between regions, so the channel number was just a local implementation detail. There is/was also usually some more or less common order of stations, e.g. in Germany you'd always put ARD on 1, ZDF on 2, the regional "third" station on 3...
- kd5bjo 7y ago
  For a long time in the US (maybe still?), the vast majority of the schedule was set by the local station. Being a member of one of the national networks brought access to a catalog of shows, and a few requirements about the scheduling of shows that the network really cared about. In almost every nationally-produced promo you got the phrase “check your local listings” in addition to the advertised time because the local station might air the show sometime other than when the network recommended.
ztetranz 7y ago
In Australia they have (or least used to have) channel zero. For many years "channel oh" was the Ten Network in Brisbane.
dbcurtis 7y ago
It has to do with how to hit a consumer price point with a receiver for a complex modulation scheme using only a couple dozen active devices and cheap-to-manufacture filters. Original NTSC monochrome television is a 6 MHz wide channel, the video carrier is 1.25 MHz up from the bottom, and at the transmitter a filter lops off most of the lower sideband. For receivers, the problem is the IF filter. Filters with steep skirts are hard to build and align, and are expensive. So... channel allocation was done with the assumption that most consumers would have receiving sets with poor adjacent-channel rejection because of using cheap filters. This was solved by channel allocation -- do not let two stations with overlapping grade-A signal contours be on adjacent channels. Problem solved. In the very early days in the US, channel 1 was 48-54 MHz. They found out that the percentage bandwidth was too wide to be able to build a practical transmitting antenna for channel 1. The SWR was too high at the band edges, and high SWR on analog TV means the transmission line generates ghost pictures. So channel 1 was dropped. Now hams have the 6 meter 50-54 MHz band, and cheap license-free R/C toys and walkie-talkies have 48-50 MHz. Channel 2 is 54-60, 3: 60-66, 4: 66-72 and then a gap: 72-74 is radio control, then channel 5 is 74-80, and so forth, and if I recall correctly there is a big gap between channels 7 and 8 so even though they are sequential numbers they are not frequency-adjacent channels. (7 and below being the so-called "low VHF" and 8-13 the "high VHF" TV channels.) The 2 MHz gap between channels 4 and 5 was also used to advantage, as it was enough to eliminate the adjacent-channel interference problem on reception. I recall when I lived in Minneapolis, that channels 2, 4, and 5 were all allocated in the metro area. Channel 3 was Mankato, far enough away that if you lived between Minneapolis and Mankato you could receive all of those stations without interference problems, being in the grade-B signal contour of both. And..... this entire post contains obsolete information of historical interest only, and even at that, of interest to very few. Now... excuse me because I have to readjust the spark gap on my 200 meter transmitter...
- ThinkingGuy 7y ago
  The US Department of Commerce publishes a wall chart showing how the difference parts of the spectrum are allocated to different services. Notice how bands for "Broadcasting (Television)" are broken up and interspersed with those for other services such as aeronautical navigation and FM radio, despite the TV channels having consecutive numbers: https://www.ntia.doc.gov/files/ntia/publications/january_2016_spectrum_wall_chart.pdf https://www.ntia.doc.gov/files/ntia/publications/january_201...

ac29 7y ago

I've lived in the US for many decades and work in commercial radio, and this is the first I've heard of there being channel numbers for analog broadcast FM radio (as opposed to frequencies). I have seen channel numbers or designators like "Blue Dot" sneak into infrequent parlance in lieu of frequencies assigned by the FCC in other bands. But, this is increasingly uncommon, or in the latter case, based on manufacturer specific use. Not terribly surprised though, Title 47 is crusty and full of surprises - these channel numbers are certainly defined somewhere.

drmpeg 7y ago
It's funny that nobody has ever changed the frequency units from Mc/s to MHz. https://www.law.cornell.edu/cfr/text/47/73.201 https://www.law.cornell.edu/cfr/text/47/73.201
- ac29 7y ago
  Ha, it had to be somewhere. The last I recall hearing "megacycles" was in Bond movies from the 1960s. Wikipedia says this was 1960: https://en.wikipedia.org/wiki/Hertz#History https://en.wikipedia.org/wiki/Hertz#History You can see why I say Title 47 is crusty.
  - ztetranz 7y ago
    Lots of old hams say "kay cees" and almost get offended when a newcomer says kilohertz.
reaperducer 7y ago
I've lived in the US for many decades and work in commercial radio, and this is the first I've heard of there being channel numbers for analog broadcast FM radio Then the station you work for must not have any repeaters or translators. When you hear a legal ID like "KHNH/Randoville, K226AR/Hacktown," the translator it got its call sign because it's on channel 226. All of the AM frequencies have channel numbers, too. I worked in radio for ten years, and wasn't even on the technical side, and I knew this.

saagarjha 7y ago

I’m curious why they start at 200.

Aloha 7y ago
There used to be another FM band around 6 meters