No sound onair after fading in Outside Broadcast feed

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Aldo263
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No sound onair after fading in Outside Broadcast feed

Post by Aldo263 » Mon Jul 10, 2017 1:10 am

I am having challenges with an OB signal.In the studio I am receiving the signal very clearly on the desk and can clearl hear it when I pre-fade it but the moment I fade in the audio nothing goes onair.In the studio I continue getting the audio well and program output levels actually show that there is something being pushed out but still nothing goes on air.I later on discovered that there are some receivers which are receiving the off air signal well but on some receivers there is nothing once I fade in the OB feed please assist techs.

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kkiddkkidd
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Re: No sound onair after fading in Outside Broadcast feed

Post by kkiddkkidd » Mon Jul 10, 2017 5:15 am

Just guessing and am assuming that you are running stereo. I don't know what an "OB" feed might be.

Are you 100% certain that both sides of the stereo pair are in phase the entire length of your air chain? If you have one side of a stereo signal reversed, you will hear little to nothing on a mono radio and a stereo radio will play audio but sound very odd. Especially if it is a mono (ie, voice) cut. It is actually playing fine but if one side of the stereo pair is reversed it is being canceled by itself...

Good luck,



Aldo263 wrote:
Mon Jul 10, 2017 1:10 am
I am having challenges with an OB signal.In the studio I am receiving the signal very clearly on the desk and can clearl hear it when I pre-fade it but the moment I fade in the audio nothing goes onair.In the studio I continue getting the audio well and program output levels actually show that there is something being pushed out but still nothing goes on air.I later on discovered that there are some receivers which are receiving the off air signal well but on some receivers there is nothing once I fade in the OB feed please assist techs.
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w9wi
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Re: No sound onair after fading in Outside Broadcast feed

Post by w9wi » Mon Jul 10, 2017 5:37 am

For what it's worth, "OB" is European for "remote".

(I think it stands for "Outside Broadcast")
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TPT
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Re: No sound onair after fading in Outside Broadcast feed

Post by TPT » Mon Jul 10, 2017 5:59 am

Yes--sounds like a phase reversal. Understand in stereo broadcasting the audio fed into the transmitter consists of a mono main channel signal ( the Left and Right channel added in phase) and a Left and inverted Right (-R) signal fed into the stereo subcarrier. So...

Let's assume the remote broadcast is coming in by a digital feed--a Barix box, for example. Remote tech gets in a hurry and reverses the wiring on the left channel (red wire hooked to to where the black wire should go). In studio, on a stereo monitor-sounds kind of OK. Goes to transmitter & stereo generator/processor. Transmitted with left channel still out of phase.

Guy listening on table radio-- Out of phase left channel audio mostly cancels out audio from right channel--so mono signal sounds faint, muddy.
Neighbor listening on his car radio--sounds a little strange, but car radio left and right speakers at full volume...
His friend back in the boonies listening on his car radio--strong signal audio is load and clear, dips behind a hill, radio switches to mono--sound goes away.

One quick check --if the mixing board allows--is if the board has separate metering for audition and mono channels. If the audio looks normal on the program meters, but you can send the same signal to mono & a separate VU meter, --the level will be much lower due to phase cancellation.

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KPJL FM
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Re: No sound onair after fading in Outside Broadcast feed

Post by KPJL FM » Mon Jul 10, 2017 7:06 am

Seems like your off-line monitoring is one channel only, but it is stereo on the board. If the stereo on the board is out of phase, there will be nearly complete cancelling of the right/left channels, sum of which is no audio on-air. Swap the hi and lo of the left channel only at the board (fader) input and see that fixes your problem.
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Re: No sound onair after fading in Outside Broadcast feed

Post by RodeoJack » Mon Jul 10, 2017 1:13 pm

For the canceling to be heard as described, a monaural board monitor would have to be a sum of both channels. Merely sampling one side or the other would result in good audio regardless of phase.

If the poster has control of the audio processor (he didn't say if he was AM or FM), he could try turning his pilot on or off while listening to a stereo receiver. If his source is out of phase, the audio would disappear with the pilot off, and sound like it's coming from the sides of the room with it on.

There's always the likelihood the outside source is originating the signal this way, which raises an interesting question (to me, at least). Would good engineering practice suggest you insist the originator fix the problem first, or could you be flexible enough to have the ability to reverse polarity on one side of an incoming feed... a pushbutton back in the rack room perhaps?

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