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Out of phase program audio = loss of range.

T

TomZ

Yup. I did it...

During a hurry-up SAGE ENDEC install meeting a scheduled RMT I dropped the ball and wired one channel out of phase with the other. The SAGE worked perfectly but the listeners began to complain about poor reception on table top radios.

My car radio was getting good fringe reception but the cheap radios were mixing the L+R to the speaker resulting in static and unstable audio.... go figger.
 
I hate to admit I did it, but a year ago I somehow got the phase flipped out of phase on one of our new remote stations. I really feel the Tieline unit I have on that site might have a flip internally, but it was an easy fix to switch so I just did it elsewhere. Anyway, the syptom was I have several people tell me that every so often our "audio would just drop out" then come back. Some were reporting really low audio all the time. When I got to the remote station town and approached I realized what had happened. With the excellent car radios made by GM (and others I presume), blending was playing a little game with the listeners and even myself. It was very bizzare. I thought to bring my Pira modulation analyzer with me and put in into L+R mode and notice the error of my ways. Since then it's been working great :). LOL! That's the first time I've ever had one flipped over like that. (normally I'm just careful about wiring where it doesn't happen)
 
Good reason to have a mono silence alarm...it will trigger on out of phase audio...don't ask me how I know this.
 
TomZ said:
Yup. I did it...

During a hurry-up SAGE ENDEC install meeting a scheduled RMT I dropped the ball and wired one channel out of phase with the other....
Click to expand...

Did that at my TV station with the original Sage 1822 back in 199-whatever. During prime-time, too...pulled the bypass patches and the calls started rolling in...lots more people with mono-sound TV's back then. Slammed the patches back in and went into shame mode.
 
The Phase Chaser would do swap phase if there was a lot of ambiant noise (birds, water falls, etc.). Take it a few seconds of normal center audio to fix itself.
 
I ran into a slightly different problem with phasing a few years ago. Station audio was perfectly in phase, until we ran an EAS test...no tones played on the air.

What had happened was that there was a phase reversal on one of the stereo pairs upstream of the EAS box, and another flipped pair downstream. As long as the EAS was just passing audio through, the two sets of flipped connections corrected each other. Once the EAS box went online with tones, the downstream flipped pair caused phase cancellation and the EAS tones were completely notched out.
 
I also managed to do this with one of those push on connectors on the back of a DA. Missed it by one pin. Sounded OK in the control room, in the car it was a disaster. I'm sure I broke the speed limit getting around the block and back into the parking lot.
 
I botched this before but I can't remember if it was a connector or on a punch block. Swapped phase on a stereo channel by mistake. Listeners would call to report intermittent dead air. It was an oldies format, and when mono tracks would play the channels would almost completely cancel each other.
 
Many years ago, I adjusted the stereo generator at a local FM station for the best separation ... I didn't bother to listen to the mono mix.
Oops. The stereo separation was great. The two channels were also out of phase. That's what happens when you don't have a 'scope' to look at the baseband.
It was fortunate that I noticed the problem before anyone complained. I also found that the original audio wiring into the transmitter was out of phase.
I reversed the wiring on one channel.
 
No matter what our Mamma's said; two wrongs can make a right.

But two pluses cannot make a negative. Yeah, right!
 
Does anyone remember the promo CD of Wilson Phillips' "You're In Love" from the early 1990s? It was produced out of phase and both channels canceled when listening in mono.
 
No, but I had an oldies formatted radio station that was endless headaches due to questionable source material. I finally put a Howe Phase Chaser in the line and solved 99% of phase related issues.
 
It happens in the UK, too! I know of a station suffered this on a intermittent basis. Every now and then, a track would have the dis-embodied vocal effect over the air. It was a CHR station so what baffled most of the staff was that when the same track got played later in the day, it was fine. It took a bit of head-scratching before somebody realised that one of the 4 automation channels was wired incorrectly to the console ;D

There was also another incident where the Left/Right channels were swapped on one of the channels, and everytime a Beatles track was played through that channel, a few clever people would ring in with "your speakers are back to front" 8)
 
Imagine the fun that out-of-phase audio will wreak on an AM signal! -125%/+98% peaks anyone?? I've fixed more than a couple AM sites with exactly this problem. It usually only becomes apparent as someone tweaks the asymmetry on the processor to find they can't get any positive spread at all.

"Our modulation sucks! I think we need a tube or something"

"ya don't say... Notice the negative peaks go up when you crank the pot? Shut it off and give me about 60 seconds!"
 
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