Modifying FM for FM Translators

[kfbkfb]

FCC rules for adjacent channel FM signals are based on +/- 75kHz deviation.

How about using +/- 15kHz for FM translators on adjacent FM channels (with a bandpass filter applied to the FM output to make sure the signal is only 30kHz wide [no sidebands]).

Existing FM radios would receive the lower modulation signal, the only difference between the 15kHz FM signal and current 75kHz FM signal would be the resulting volume would be lower.

I haven't done any calculations, but it seems like a more limited bandwidth FM signal could fit in a channel adjacent to a standard FM signal.


Kirk Bayne

 

[Kelly A]

Good Lord!

 

[PTBoardOp94]

So, no stereo, let alone quad?

 

[davideduardo]

So, no stereo, let alone quad?

In FM "loudness" is measured in bandwidth. It is, of course, frequency modulation. If you take an existing station and (ignoring stereo and any SCA) modulates 100%, it uses + and - 75 kHz. Of course, 100% modulation is an arbitrary measure, as it could just as well be + / - 100 kHz or + / - 50 kHz. But in the comparison of the US standard of +/- 75 kHz, a station doing +/- 15 kHz is going to be significantly less loud than the other stations.

The loudness comparison is measured in db's and I'm not going to try to explain logarithms any more than I am going to try to compare a 7.1 and a 7.9 earthquake to someone who thinks that they are only about 12% different.

 

[kfbkfb]

So, no stereo, let alone quad?

Tragically, no.


Kirk Bayne

 

[Kelly A]

Tragically, no.

So no stereo, and audio levels that are roughly one quarter of every other station on the dial? Oh yeah, that would be a popular proposal. Not.

 

[Miss Tuned]

This is a joke, right?

FM stands for Frequency Modulation. You modulate the signal by changing the frequency. Less deviation, lower audio, no listeners. Surely this thread needs to be closed/binned - it isn't going to lead to any kind of serious discussion or debate because it's a technically illiterate and wholly unserious idea from someone who specializes in posting this half-baked dross.

@kfbkfb - are you being serious, or are your threads attempts at humor?

 

[kfbkfb]

My idea is to squeeze more (compatible format) FM signals into the existing FM band without causing more interference with existing FM stations.

I know my idea of lower (FM) bandwidth FM signals would result in lower volume on existing FM radios, there could be occasional "PSAs" to turn up the volume on your FM radio to listen to these new format FM translator signals and if my idea catches on, new FM radios could use an ID signal broadcast in this lower FM bandwidth signal to cue new FM radios to automatically turn up the volume.

edit:
My idea isn't a joke, I'm trying to devise a compatible FM signal (selecting the FM deviation is arbitrary, for USA FM radio it's +/- 75kHz, for [old] NTSC TV, the FM [which did contain stereo + SAP] was +/- 25kHz).

another edit:
Further thought - stereo [and even the FCC approved quadraphonic] could be in this new low FM bandwidth signal.

anyway - I just thought I'd throw my idea out there - looks like it isn't going anywhere


Kirk Bayne

 

[R.D.P.]

Leave the FM band alone. It's doing fine as is. 👍

Dan <><

 

[valvashon]

This is a terrible idea. I grew up in Fargo, ND, where you could listen to WDAY channel 6 by tuning your FM radio to the end of the dial to 87.7 (.75 if you had an analog tuner). While you could hear it the audio wasn't particularly listenable as any available tuner was expecting +/- 75 kHz deviation meaning you had to turn the radio way up with the associated background hiss.
Expecting anybody to listen to a translator with even less deviation on existing radios is a tremendous ask. If you want to put the nail in the coffin for AM revitalization translators, or even any translator, this is it. There are zillions of existing radios and expecting people buy new ones just to listen to translators at the same perceived volume level as full power stations is ludicrous.

Val

 

[kfbkfb]

I'm serious - my lower bandwidth FM signals wouldn't require new FM radios and could allow more FM translators in the existing FM band without causing interference.

No existing FM stations (full or LPFM) would be affected in any way.

As I mentioned, the USA was already transmitting FM with 2 different formats - 75kHz for FM and 25kHz for [NTSC] TV, maybe 25kHz instead of 15kHz would work for my idea.

edit:
Very important - no new FM radios would be required, all existing FM radios would work, the only "penalty" would be lower volume from these new low bandwidth signals.

(looks like my idea isn't going anywhere)


Kirk Bayne

 

[davideduardo]

(looks like my idea isn't going anywhere)

It's going rapidly somewhere... the the same place Christian preachers threaten we'll go if we misbehave. 😳

 

[Kelly A]

My idea is to squeeze more (compatible format) FM signals into the existing FM band without causing more interference with existing FM stations.

But what you don't seem to comprehend, is there are standards for broadcast in FM and stereo, whether it's a translator or a full-class station. Your proposal would create a different standard that would not only require existing stations with translators to replace those translators, but would create a different listening environment that undoubtedly would negatively impact existing translators. If I had an existing station with translators, I'd give your idea of trying to cram in more translators, the finger.

I know my idea of lower (FM) bandwidth FM signals would result in lower volume on existing FM radios, there could be occasional "PSAs" to turn up the volume on your FM radio to listen to these new format FM translator signals and if my idea catches on, new FM radios could use an ID signal broadcast in this lower FM bandwidth signal to cue new FM radios to automatically turn up the volume.

I'm sorry, but clearly you don't know anything about listeners.

edit:
My idea isn't a joke,

It should be, because it is.

 

[valvashon]

Wow- David Eduardo liked one of my posts. I guess I have arrived.
Back to this wildly off the rails proposal- the reason that there was a +/- 75 kHz deviation standard and a +/- 25 kHz deviation standard was because the two standards were used on two different types of receivers, analog TV and FM. As these receivers were used in different ways and with different types of signals you could get away with the two different standards. As I pointed out listening to TV audio on an FM radio was possible but not terribly enjoyable. Your proposed translator modulation standards would sound the same or worse on an existing radio.
I'm not totally sold on digital radio broadcasting, but if we have to buy new radios for a new FM broadcasting standard that standard should be an open source, license free DAB standard, not a tweak to the existing analog modulation standard. If that's the case do the same to the AM band, assuming that the DAB standard is compatible for the MW frequencies involved.
One new radio with seamless tuning between the bands might be acceptable, although that might not even save radio as we currently know it.

Val

 

[Miss Tuned]

I'm not totally sold on digital radio broadcasting, but if we have to buy new radios for a new FM broadcasting standard that standard should be an open source, license free DAB standard, not a tweak to the existing analog modulation standard. If that's the case do the same to the AM band, assuming that the DAB standard is compatible for the MW frequencies involved.
One new radio with seamless tuning between the bands might be acceptable, although that might not even save radio as we currently know it.

Val

DAB is a totally separate frequency band - it sits in Band III VHF (around 180-240 MHz) and the frequencies are currently in use for TV broadcasting in the US, channels 7 through 13.

You can't put DAB on either the current FM or AM broadcast bands - it's very much its own separate technology. On e.g. car radios in countries where DAB is in use, it appears as a separate "band": you choose FM, AM (on a decreasing number of radios) or DAB. On the DAB "band", you choose the station from an alphabetical list of all the stations available in your area, frequencies are invisible.

 

[davideduardo]

Wow- David Eduardo liked one of my posts. I guess I have arrived.

I always enjoy your posts. Before that I did not even know where Vashon Island was!

 

[kfbkfb]

I'm sorry, but clearly you don't know anything about listeners.

True - my FM scheme is probably technically possible, but the inevitable volume loss seems like an insurmountable obstacle for listeners.


Kirk Bayne

 

[valvashon]

DAB is a totally separate frequency band - it sits in Band III VHF (around 180-240 MHz) and the frequencies are currently in use for TV broadcasting in the US, channels 7 through 13.

You can't put DAB on either the current FM or AM broadcast bands - it's very much its own separate technology. On e.g. car radios in countries where DAB is in use, it appears as a separate "band": you choose FM, AM (on a decreasing number of radios) or DAB.

By DAB I meant Digital Audio Broadcasting in the royal sense, not DAB as in the actual standard in use in other parts of the world. Although if there is no technical reason why you couldn't use that standard it seems as if you could do a digital switchover as we did for TV back in 2008 or whenever it was. Shutting off all the analog FM and AM signals and then firing up with digital audio encoding in their place at the stroke of midnight on a given day might be a big ask. The advantage of ATSC (generally) and the HDTV signals were readily apparent.
The advantages of digital audio might not be as readily apparent to the average radio listener. Streaming was barely there when HDTV suddenly became available from OTA broadcast stations. Today that switchover for OTA might not even happen and because of the ease of streaming audio these days radio may be stuck with analog modulation schemes.

Val

 

[kfbkfb]

Shutting off all the analog FM and AM signals and then firing up with digital audio encoding in their place at the stroke of midnight on a given day might be a big ask.

There are a few HD digital radio only signals in the AM band, although HD digital radio only signals can be used in the FM band, I know of no HD digital radio only signals currently in the FM band.


Kirk Bayne

 

[Miss Tuned]

By DAB I meant Digital Audio Broadcasting in the royal sense, not DAB as in the actual standard in use in other parts of the world. Although if there is no technical reason why you couldn't use that standard it seems as if you could do a digital switchover as we did for TV back in 2008 or whenever it was. Shutting off all the analog FM and AM signals and then firing up with digital audio encoding in their place at the stroke of midnight on a given day might be a big ask. The advantage of ATSC (generally) and the HDTV signals were readily apparent.
The advantages of digital audio might not be as readily apparent to the average radio listener. Streaming was barely there when HDTV suddenly became available from OTA broadcast stations. Today that switchover for OTA might not even happen and because of the ease of streaming audio these days radio may be stuck with analog modulation schemes.

Val

Nobody has yet turned off FM radio in favor of digital radio. Norway is closest to having done so - all of its major networks are digital-only now, but there are still some FM stations on the air, mostly specialist and smaller local stations. Switzerland is in the process of a switchover, but I don't know how far through they are with it. The UK is the country with the longest-standing DAB network, and FM is still in heavy use (it's still about 33% of listening).

I don't think there'd be a market for yet another digital radio standard - there's already HD Radio and DAB, which offer different things to suit different markets - HD Radio suiting the more fragmented US market better, while DAB supports more regulated radio markets in the likes of Europe. France started to try out its own DMB standard years ago, but is now rolling out DAB (specifically, DAB+ which uses more modern audio encoding) in line with the rest of Europe.

As you say, the time is nearing where IP will be the default - mobile coverage is getting better and better, it's already the main way I listen to radio in my car, and at home I use a smart speaker rather than a DAB radio. Fiddling with broadcast modes, whether that's messing with FM as in the OP's hare-brained idea or rolling out a new digital radio standard, seems a bit like a case of shutting the stable door with the horse five miles down the road.