Two Programs from One Transmitter

As long as the seperation was good it would work quite well. I've thought of this as well, turns out for full power stations this is specifically forbidden.

WJXQ in Jackson Michigan experimented with that very same affect.

Good feedback, by the way, and another trick available to FM experimenters.

Imagine doing the same thing with a stereo stream on the internet.

Two mono program channels, but a smooth way of fading to stereo when programs are broadcast in stereo. This makes sense for stations like KDX, where our classical concerts are stereophonic, but all the talk shows are mono.

I can see experiments in the future!

The Minnesota News Network had been doing this for over 20 years. They were recently bought out by Learfield, so things have changed, but for decades I'd go to work and have a look at the schedule for the day. They had two satellite channels, cleverly called 1 and 2.  These were stereo channels, so we actually had 1L and 1R, 2L and 2R.  The news feed was always on 1L.  Ag programming may be on 1R, and the Minnesota Twins game could be on 2L while a Timberwolves program was on 2R.  Did this for decades, worked just fine. Each channel was wired into the patch panel and control board as separate mono feeds.

Back in the 1980's I was working at KZZY-FM in Devils Lake ND.  We covered high school basketball and found ourselves in a position where we had two teams heading to the tournament and we really wanted to carry two games at once. We promo-ed the heck out of it, and then put one game on left, one on right -- using the production studio for one game, the regular air studio for the other. Worked fine with more than enough separation.  Except for the people who had mono radios!  LOL. But it worked.

TIB

That is a very common practice for sat nets. Texas State Networks does the same thing.

Back in the mid 60s I worked at an FM station that used a "subcarrier" to transmit CBS news to 4 other stations for rebroadcast.  Those other stations also carried the state news fed by our FM transmitter, originating from our studio.  Kind of a mini-network.  At another FM stereo station, we used the "subcarrier" to send motivation music to businesses.  Is this the same kind of thing this thread is about?

Sort of related--in the early days of FM in this area, a nearby station broadcast a few programs in 'stereo', using its mono FM transmitter for one channel and its AM transmitter for the other channel.  So, the listeners had to set up two radios (an AM and an FM) to hear the stereo signal.  Kind of interesting at the time, but FM stereo wasn't far behind so that early experiment kind of faded away.

Morningdj the service you are talking about is "SCA" the subcarriers at 67khz and 92khz. FM has a lot of unused bandwith that allows Stereo, SCA, and RDS to all be carried at the same time.

This morning I opened two instances of Winamp, each operating in stereo mode.

One Winamp Playlist was carrying "The Alex Jones Show" and the balance control was set to feed the left channel.

The 2nd Winamp Playlist was looping a low level pulsing sound set for the right channel.

The Shoutcast stereo stream, unfortunately for the test, could only be heard on mono portable radios, as I do not have stereo computer speakers. All my monitoring is done on portable radios in mono. Therefore I heard a blend of the two audio feeds.

The Studio Transmitter link feeding the AMT5000 Transmitter is sent by a Ramsey FM30B Transmitter which I set for stereo mode, and received on an early Panasonic stereo receiver which I set for stereo.

Something seems to be wrong with the stereo reception on the Panasonic receiver, the balance control did not allow favoring the left or right channel, it constantly heard only a mono mix of the two audio tracks.

We'll need more equipment and different setups to properly test sending two separate programs on left and right stereo channels.

The next test has been moved to the bottom of the priority list and may be conducted in 2025.

You will likely always hear bleedover on any consumer grade reciever or transmitter. A home theater tuner might be able to separate it enough however. Another feature to take into account is the stereo blend feature many radios have, as the signal gets weaker the radio forces it more and more into mono mode slowly eating away at the separation.

Split programing may be easier to do on AM.  A unique transmitter would need to be built that could modulate above the carrier (upper side band) with one program and below the carrier (lower side band) with another program.  Then depending which side the listener’s radio was demodulating they would hear one program or the other.  Some radios only look at the upper side band, some only look at the lower side band, and some may use both?

It is a neat idea to use one transmitter for multiple programming but it is simpler for Part 15 operations and doesn't require anything special of the receiver or listener to use more than one transmitter on different frequencies.

In a way, I do this here even though I didn't give it any thought in terms of "split programming". My FM transmitter is for the wife and programs classical music, and the AM transmitter is for my programming tastes.

The transmitters could just as well be in the same band on different frequencies.

Neil

The questions about sending two simultaneous programs by way of one transmitter or on a single stream are experimental "brain storming" ideas, as has been obvious.

If it were done it would be a way of sending double the content using a minimum of transmission paths, hoping to enlarge the audience at the other end.

Now it occurs to me that the ultimate use of this approach would be in the hands of the listener, who would be able to chose between program A or program B.

It would not give a listener a chance to listen to two programs at the same time, which is interesting to think about...

This morning for example, my stream is on the air and might normally be carrying a program that I'd be enjoying, but I happen to be listening to some off-line audio for the next Low Power Hour, and try as I might, I cannot listen to two different programs at the same time.

The brain is a serial device and is monophonic.

Because we have two ears, you's think we could separate the left ear from the right ear and hear two different programs, but the brain cannot concentrate on both programs... it can only focus on one or the other... unless you are willing to perceive the sound as a chaotic jumble of voices talking.

Perhaps that explains why the FCC is insane... they have heard too many radio stations for too long a time.

We humans, and indeed many other creatures, have evolved with two ears for the purpose of locating prey or threats. For this to work, the two signals (one from each ear) need to be combined and analyzed in a single processor area, or multiple parallel processors, so the phase, amplitude, and frequency information can be used to extract distance and direction. Our "monophonic" brains result from this combining of the signals.

Some owl species have one ear lower on their heads than the opposing ear which gives them better sonic location abilities when they are perched in trees seeking prey on the ground.

It is interesting that many species of birds have defensively adapted to this hearing ability of their predators by signalling with "chirps" which confuse the distance/direction determining abilities of the hunters.

I have no idea how this relates to broadcasting and music but anticipate that Carl will figure this out.

Neil

For one thing we could hang a weight around one ear to eventually make it sag lower than the other ear, giving us better direction finding at home, so we'll be able to keep track of where the wife is at all times.

Another thing to try is get one monitor speaker lower than the other in stereo setups, which will cause the listeners to tilt their heads.

At the outset we do not know what benefit to expect from tilting the head. I expect all our thoughts will migrate to the lowest side.