• Get involved.
    We want your input!
    Apply for Membership and join the conversations about everything related to broadcasting.

    After we receive your registration, a moderator will review it. After your registration is approved, you will be permitted to post.
    If you use a disposable or false email address, your registration will be rejected.

    After your membership is approved, please take a minute to tell us a little bit about yourself.
    https://www.radiodiscussions.com/forums/introduce-yourself.1088/

    Thanks in advance and have fun!
    RadioDiscussions Administrators

FM Stereo Question

TimmyWA

TimmyWA

I saw in an earlier post that a High School was broadcasting 2 different games on one station, one on the left channel and the other on the right. The response to this was negative. Why? I know it seems almost infantile to use the station in this manner. Is there some legality involved? I can see this as some way a low-budget class A FM station to "multi-cast" maybe jazz on one channel and top 40 on the other?? Two mono FM stations both advertising and making money, on one frequency... There must be some reason this isn't happening. Can you all tell me why.
Thanks!

-Timmy<P ID="signature">______________
Perfection is overrated...</P>
 
> There must be some reason this
> isn't happening. Can you all tell me why.

I can give you one VERY good reason. Lack of discrete separation in modern FM receivers.

Here's the in-depth explanation...FM stereo receivers are inherently more noisy at the fringe of the signal area than FM mono receivers. To reduce the noise, most FM receivers have a mixing circuit that monitors the stereo output and mixes in a level of monaural signal to reduce the noise level as the vehicle travels through an area of fringe-level reception (or tall buildings, or hills, or anything else that reduces signal level).

The end result is that most FM receivers pass reduced stereo separation as signal level from a given station decreases.

Given that most high-school operated stations have considerably less power than commercial stations, the amount of such a station's listening area considered as fringe level (as far as the receiver's design is concerned) could approach 90%.

This means that, try as you might, keeping right-channel output out of a listener's left-channel output, or vice-versa, is a near impossibility.

Good idea, but no cigar today.

Later...
Matt Smith, Station Manager
WGSR-TV "Star-39"
Reidsville, NC
 
That is so stupid - it is absolutely brilliant! Multicasting without IBOC. I think only sports on each channel could get away with it - there is so much noise from the crowd you wouldn't notice crosstalk. Of course all the people with mono receivers would get a mix. But most high school game announcers are silent most of the time, so it might actually be listenable the majority of the time.
 
> > There must be some reason this
> > isn't happening. Can you all tell me why.
>
> I can give you one VERY good reason. Lack of discrete
> separation in modern FM receivers.
>
> Here's the in-depth explanation...FM stereo receivers are
> inherently more noisy at the fringe of the signal area than
> FM mono receivers. To reduce the noise, most FM receivers
> have a mixing circuit that monitors the stereo output and
> mixes in a level of monaural signal to reduce the noise
> level as the vehicle travels through an area of fringe-level
> reception (or tall buildings, or hills, or anything else
> that reduces signal level).
>
> The end result is that most FM receivers pass reduced stereo
> separation as signal level from a given station decreases.
>
> Given that most high-school operated stations have
> considerably less power than commercial stations, the amount
> of such a station's listening area considered as fringe
> level (as far as the receiver's design is concerned) could
> approach 90%.
>
> This means that, try as you might, keeping right-channel
> output out of a listener's left-channel output, or
> vice-versa, is a near impossibility.
>
> Good idea, but no cigar today.
>
> Later...
> Matt Smith, Station Manager
> WGSR-TV "Star-39"
> Reidsville, NC
>


Good Info, Matt. Let's just say for the sake of arguement, that this signal weakness issue is not part of the story. 1.21 GigaWatts of Pure ERP!!


-Timmy<P ID="signature">______________
Perfection is overrated...</P>
 
> That is so stupid - it is absolutely brilliant!
> Multicasting without IBOC....

This is already possible. Every Licensed FM Station has the ability to easily add two additional audio channels in addition to the main channel. This is done by using the 67khz and 92khz sub-carriers. You find many sub-carriers in use in the urban centers like New York City as a means to broadcast ethnic programming. The license holders actually lease these sub carriers out to the ethnic broadcasters. Unfortunately you need a special receiver in order to hear the sub-carrier channels. The good news though is that there are some very affordable options out there. There is a nice portable and tunable AM/FM/SCA radio available for about $29.00 (order from web site)

So the real question is: Why dont we see more widespread use of Sub-Carrier channels. Think of this. If SCA detection was as common as FM Stereo radios, then the HS radio station could carry one game on the 67K channel, the second game on the 92K channel, and keep their regularly scheduled programming on the main channel. I just don't get it why this stuff isn't easily available for the general public consumers. Its like RDS and AM Stereo. Although RDS has recently picked up the past year or so.
 
One word - RECEIVERS. They aren't being sold, almost nobody knows about the capability.

If IBOC had been done right, they would have realized that they could multicast, and replace all the stuff up there with the digital sidebands, and improve SCA, reading for the deaf, RDS, and everything else up there in the process. It would just take new receivers. Instead - they leave all that stuff in tact, and put the digital hash on adjacent channels. BAD NEWS for people in tightly packed fringes!
 
IIRC, thats illegal. What you broadcast needs to be mono-compatible if I remember the FCC rules. Which isn't to say that its not being done.

Of course, there's no law that prohibits a radio station from broadcasting two unrelated audio sources at once on BOTH left and right channels...which seems to happen a lot since radio stations started running unattended with PC-based automation. Thats just bad programming or engineering...




> I saw in an earlier post that a High School was broadcasting
> 2 different games on one station, one on the left channel
> and the other on the right. The response to this was
> negative. Why? I know it seems almost infantile to use the
> station in this manner. Is there some legality involved? I
> can see this as some way a low-budget class A FM station to
> "multi-cast" maybe jazz on one channel and top 40 on the
> other?? Two mono FM stations both advertising and making
> money, on one frequency... There must be some reason this
> isn't happening. Can you all tell me why.
> Thanks!
>
> -Timmy
>
 
> One word - RECEIVERS. They aren't being sold, almost nobody
> knows about the capability.
>
> If IBOC had been done right, they would have realized that
> they could multicast, and replace all the stuff up there
> with the digital sidebands, and improve SCA, reading for the
> deaf, RDS, and everything else up there in the process. It
> would just take new receivers. Instead - they leave all
> that stuff in tact, and put the digital hash on adjacent
> channels. BAD NEWS for people in tightly packed fringes!
>

But BRUCE, how silly! If you kept the digital sidebands within the original 200kHz channel allocation, that would be In-Band-On-Channel (IBOC)! What the heck would iBiquity do if we defined IBOC as literally being In-Band-On-Channel?

ha...
 
> > One word - RECEIVERS. They aren't being sold, almost
> nobody
> > knows about the capability.
> >
> > If IBOC had been done right, they would have realized that
>
> > they could multicast, and replace all the stuff up there
> > with the digital sidebands, and improve SCA, reading for
> the
> > deaf, RDS, and everything else up there in the process.
> It
> > would just take new receivers. Instead - they leave all
> > that stuff in tact, and put the digital hash on adjacent
> > channels. BAD NEWS for people in tightly packed fringes!
> >
>
> But BRUCE, how silly! If you kept the digital sidebands
> within the original 200kHz channel allocation, that would be
> In-Band-On-Channel (IBOC)! What the heck would iBiquity do
> if we defined IBOC as literally being In-Band-On-Channel?
>
> ha...
>

OK.. here's a legality question for you guys. Is it legal for let's say an AM station to sell SCA radios or direct the public to buy SCA radios and simulcast their signal on an FM SCA to fix signal coverage issues? Is an SCA for public broadcast consumption, or must it just be for subscription/rented aplications or station use only?

This is something I always wondered for challeged AMs within a cluster that has powerful FMs with unused SCA capabibilities. For 29 bucks, I'd think there would be quite a few people that listen to some AMs that would jump at getting it without all the noise, etc. I mean, let's face it. There's some places even the most powerful AMs don't work well. One place is typically an office with computer noise, etc.

BTW.. The radios I found that work best are @ www.RadioSCA.com for 29.99.



<P ID="signature">______________
--- THE Insultant ---</P>
 
> > > One word - RECEIVERS. They aren't being sold, almost
> > nobody
> > > knows about the capability.
> > >
> > > If IBOC had been done right, they would have realized
> that
> >
> > > they could multicast, and replace all the stuff up there
>
> > > with the digital sidebands, and improve SCA, reading for
>
> > the
> > > deaf, RDS, and everything else up there in the process.
>
> > It
> > > would just take new receivers. Instead - they leave all
>
> > > that stuff in tact, and put the digital hash on adjacent
>
> > > channels. BAD NEWS for people in tightly packed
> fringes!
> > >
> >
> > But BRUCE, how silly! If you kept the digital sidebands
> > within the original 200kHz channel allocation, that would
> be
> > In-Band-On-Channel (IBOC)! What the heck would iBiquity
> do
> > if we defined IBOC as literally being In-Band-On-Channel?
> >
> > ha...
> >
>
> OK.. here's a legality question for you guys. Is it legal
> for let's say an AM station to sell SCA radios or direct the
> public to buy SCA radios and simulcast their signal on an FM
> SCA to fix signal coverage issues? Is an SCA for public
> broadcast consumption, or must it just be for
> subscription/rented aplications or station use only?
>
> This is something I always wondered for challeged AMs within
> a cluster that has powerful FMs with unused SCA
> capabibilities. For 29 bucks, I'd think there would be
> quite a few people that listen to some AMs that would jump
> at getting it without all the noise, etc. I mean, let's face
> it. There's some places even the most powerful AMs don't
> work well. One place is typically an office with computer
> noise, etc.
>
> BTW.. The radios I found that work best are @
> www.RadioSCA.com for 29.99.
>

I see nothing in the FCC rules that would prohibit it. As long as you're selling fixed-frequency receivers, what you're proposing would work.

Keep in mind, though, that the subcarrier doesn't have the same coverage as the main channel. Add to that the fact that your listeners need to buy a special receiver, and you can see why that's not too widespread.<P ID="signature">______________
</P>
 
> Good Info, Matt. Let's just say for the sake of arguement,
> that this signal weakness issue is not part of the story.
> 1.21 GigaWatts of Pure ERP!!

Then every man within 5 miles of the tower will go sterile and develop testicular cancer. THEN the station can make a billion dollars running commercials for trusses, herbal cures and enzyte.

You can't win with the power game in radio.

Matt
 
> > > > One word - RECEIVERS. They aren't being sold, almost
> > > nobody
> > > > knows about the capability.
> > > >
> > > > If IBOC had been done right, they would have realized
> > that
> > >
> > > > they could multicast, and replace all the stuff up
> there
> >
> > > > with the digital sidebands, and improve SCA, reading
> for
> >
> > > the
> > > > deaf, RDS, and everything else up there in the
> process.
> >
> > > It
> > > > would just take new receivers. Instead - they leave
> all
> >
> > > > that stuff in tact, and put the digital hash on
> adjacent
> >
> > > > channels. BAD NEWS for people in tightly packed
> > fringes!
> > > >
> > >
> > > But BRUCE, how silly! If you kept the digital sidebands
>
> > > within the original 200kHz channel allocation, that
> would
> > be
> > > In-Band-On-Channel (IBOC)! What the heck would iBiquity
>
> > do
> > > if we defined IBOC as literally being
> In-Band-On-Channel?
> > >
> > > ha...
> > >
> >
> > OK.. here's a legality question for you guys. Is it legal
>
> > for let's say an AM station to sell SCA radios or direct
> the
> > public to buy SCA radios and simulcast their signal on an
> FM
> > SCA to fix signal coverage issues? Is an SCA for public
> > broadcast consumption, or must it just be for
> > subscription/rented aplications or station use only?
> >
> > This is something I always wondered for challeged AMs
> within
> > a cluster that has powerful FMs with unused SCA
> > capabibilities. For 29 bucks, I'd think there would be
> > quite a few people that listen to some AMs that would jump
>
> > at getting it without all the noise, etc. I mean, let's
> face
> > it. There's some places even the most powerful AMs don't
> > work well. One place is typically an office with computer
>
> > noise, etc.
> >
> > BTW.. The radios I found that work best are @
> > www.RadioSCA.com for 29.99.
> >
>
> I see nothing in the FCC rules that would prohibit it. As
> long as you're selling fixed-frequency receivers, what
> you're proposing would work.
>
> Keep in mind, though, that the subcarrier doesn't have the
> same coverage as the main channel. Add to that the fact
> that your listeners need to buy a special receiver, and you
> can see why that's not too widespread.

I have a receiver with a Capri SCA board from the 80s, back when they were legal to sell. From my experience, FM-SCA has bandwidth only slightly better than a "typical" AM receiver (a GOOD AM receiver can easily beat it), coverage is rather limited, and there tends to be some background hiss unless the station is bending the signal meter. I am not a big fan of HD Radio, but and HD-2 or HD-3 stream would easily sound better.
 
> I saw in an earlier post that a High School was broadcasting
> 2 different games on one station, one on the left channel
> and the other on the right. The response to this was
> negative. Why? I know it seems almost infantile to use the
> station in this manner. Is there some legality involved? I
> can see this as some way a low-budget class A FM station to
> "multi-cast" maybe jazz on one channel and top 40 on the
> other?? Two mono FM stations both advertising and making
> money, on one frequency... There must be some reason this
> isn't happening. Can you all tell me why.
> Thanks!
>
> -Timmy
>

Ga Tech's student station WREK had done exactly what you describe. It has been years... if I remember correctly, it was done because the campus station covered some of the girls sports and somebody made playoffs and they had two major things to cover at the same time. Of course, this was about 20 or 25 years ago and engineering students then did lots of strange things with campus radio.

I was the manager of a class D 10 watter at Southern Tech in Marietta, GA. We used our FM once to run the sound at the drive-in theatre next door. The drive-in was bought by the school for a parking lot. The projection booth/concession stand had been torn down, but the screen was still there. Before they removed the screen, we had one last hurrah. I don't remember the move, but we paid someone to bring in the 35mm projectors and run the movie from the back of a big truck. We took the output of the sound and fed it through the campus computer cable network back to the station. We had to have a 1000' drop cable on the ground to get us to a box to tap the campus network. Nobody even noticed the very slight delay in the sound vs. the picture... due to distance, processing, etc.
 
> > > > > One word - RECEIVERS. They aren't being sold,
> almost
> > > > nobody
> > > > > knows about the capability.
> > > > >
> > > > > If IBOC had been done right, they would have
> realized
> > > that
> > > >
> > > > > they could multicast, and replace all the stuff up
> > there
> > >
> > > > > with the digital sidebands, and improve SCA, reading
>
> > for
> > >
> > > > the
> > > > > deaf, RDS, and everything else up there in the
> > process.
> > >
> > > > It
> > > > > would just take new receivers. Instead - they leave
>
> > all
> > >
> > > > > that stuff in tact, and put the digital hash on
> > adjacent
> > >
> > > > > channels. BAD NEWS for people in tightly packed
> > > fringes!
> > > > >
> > > >
> > > > But BRUCE, how silly! If you kept the digital
> sidebands
> >
> > > > within the original 200kHz channel allocation, that
> > would
> > > be
> > > > In-Band-On-Channel (IBOC)! What the heck would
> iBiquity
> >
> > > do
> > > > if we defined IBOC as literally being
> > In-Band-On-Channel?
> > > >
> > > > ha...
> > > >
> > >
> > > OK.. here's a legality question for you guys. Is it
> legal
> >
> > > for let's say an AM station to sell SCA radios or direct
>
> > the
> > > public to buy SCA radios and simulcast their signal on
> an
> > FM
> > > SCA to fix signal coverage issues? Is an SCA for public
>
> > > broadcast consumption, or must it just be for
> > > subscription/rented aplications or station use only?
> > >
> > > This is something I always wondered for challeged AMs
> > within
> > > a cluster that has powerful FMs with unused SCA
> > > capabibilities. For 29 bucks, I'd think there would be
> > > quite a few people that listen to some AMs that would
> jump
> >
> > > at getting it without all the noise, etc. I mean, let's
> > face
> > > it. There's some places even the most powerful AMs
> don't
> > > work well. One place is typically an office with
> computer
> >
> > > noise, etc.
> > >
> > > BTW.. The radios I found that work best are @
> > > www.RadioSCA.com for 29.99.
> > >
> >
> > I see nothing in the FCC rules that would prohibit it. As
>
> > long as you're selling fixed-frequency receivers, what
> > you're proposing would work.
> >
> > Keep in mind, though, that the subcarrier doesn't have the
>
> > same coverage as the main channel. Add to that the fact
> > that your listeners need to buy a special receiver, and
> you
> > can see why that's not too widespread.
>
> I have a receiver with a Capri SCA board from the 80s, back
> when they were legal to sell. From my experience, FM-SCA
> has bandwidth only slightly better than a "typical" AM
> receiver (a GOOD AM receiver can easily beat it), coverage
> is rather limited, and there tends to be some background
> hiss unless the station is bending the signal meter. I am
> not a big fan of HD Radio, but and HD-2 or HD-3 stream would
> easily sound better.
>
KIXI Seattle was simulcasting on one of their FM's SCAs and offering SCA radios to their listeners a couple of years ago. I don't know if they're still doing it or not but it was heavily promoted on their website. I'll have to go back and check it out.
 
Status
This thread has been closed due to inactivity. You can create a new thread to discuss this topic.


Back
Top Bottom