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August 25, 2022 3:16 pm  #1


"Turn Off the Stereo On FM and See What Happens"

I'm not sure how wise this is, but CBC Radio 1 here does it, amid some controversy.

In this article, a radio veteran asks the question, 'do you really need stereo on a lower powered FM?' and makes an argument for maybe why you don't.

Here's his answer.

 

August 25, 2022 6:37 pm  #2


Re: "Turn Off the Stereo On FM and See What Happens"

I suspect the vast majority of listeners wouldn't notice the difference; more would notice a scratchy signal though.

I have a colleague in a medium market where one of their FMs was in mono for MONTHS and nobody noticed. You'd also be at an all time low for the number of people who even know what mono is.

It really makes sense on an underpowered signal, certain terrains, and certain formats.


 
 

August 25, 2022 7:13 pm  #3


Re: "Turn Off the Stereo On FM and See What Happens"

For its first few years on FM, Lindsay's CKLY was still mono, despite being a music station, but after CKLY was sold to CHUM in 2000-2001, 91.9 finally went stereo, as part of an equipment overhaul. I'm guessing the station was still feeding the transmitter with a mono audio line and/or the old AM audio processor which could not/cannot generate an FM-compatible stereo output.

I also remember hearing, for some time in 1999, a very high-pitched tone in CKLY-FM's audio... not sure what it was or what it was for, but I have a sample of it on tape somewhere.

 

August 25, 2022 7:20 pm  #4


Re: "Turn Off the Stereo On FM and See What Happens"

Forward Power wrote:

I'm guessing the station was still feeding the transmitter with a mono audio line and/or the old AM audio processor which could not/cannot generate an FM-compatible stereo output.

I wonder if this is the case for CBC on 99.1.  Their sound has a very boosted and dynamically compressed upper midrange, akin to AM on a wideband tuner.  So I wonder if they perhaps have an AM audio processor and a limiter somewhere in the chain left over from their 740 KHz days.
 


Cheers,
Jody Thornton
 
 

August 25, 2022 7:25 pm  #5


Re: "Turn Off the Stereo On FM and See What Happens"

Jody Thornton wrote:

Forward Power wrote:

I'm guessing the station was still feeding the transmitter with a mono audio line and/or the old AM audio processor which could not/cannot generate an FM-compatible stereo output.

I wonder if this is the case for CBC on 99.1.  Their sound has a very boosted and dynamically compressed upper midrange, akin to AM on a wideband tuner.  So I wonder if they perhaps have an AM audio processor and a limiter somewhere in the chain left over from their 740 KHz days.
 

The "talk" presets on FM processors often do exactly that.
 


 
 

August 25, 2022 7:41 pm  #6


Re: "Turn Off the Stereo On FM and See What Happens"

RadioAaron wrote:

The "talk" presets on FM processors often do exactly that.
 

So the engineers I take it would rarely have to mess with threshold, attack and release settings?  That almost disappoints me, because I'd like to be the architect of my "own sound".  I know the Optimod has a signature sound, but I though there was still some old schoolers that did it the old fashioned manual way.

What I still have to learn.
 


Cheers,
Jody Thornton
 
 

August 25, 2022 7:55 pm  #7


Re: "Turn Off the Stereo On FM and See What Happens"

The don't *have* to, but most still do.

My point was just that what you're hearing on CBC is more likely intentional than the result of old equipment in the audio chain.

Last edited by RadioAaron (August 25, 2022 7:57 pm)


 
 

August 25, 2022 8:21 pm  #8


Re: "Turn Off the Stereo On FM and See What Happens"

The entire Radio I nedwork is mono and it is intentional. They say it's more efficient.

Last edited by turkeytop (August 25, 2022 8:36 pm)


You don't have to be a good sport to be a mad one.
 

August 26, 2022 11:32 am  #9


Re: "Turn Off the Stereo On FM and See What Happens"

Forward Power wrote:

For its first few years on FM, Lindsay's CKLY was still mono, despite being a music station, but after CKLY was sold to CHUM in 2000-2001, 91.9 finally went stereo, as part of an equipment overhaul. I'm guessing the station was still feeding the transmitter with a mono audio line and/or the old AM audio processor which could not/cannot generate an FM-compatible stereo output.

I did hear form someone who was there at the time that when CKLY flipped to FM the owners of the day did it on the super cheap. Instead of a new site, they put the FM stick on the same swampy site. It had worked well for the AM but was not conducive to FM transmission resulting in a signal that didn't get out much past the city limits.
As part of the major technical upgrades they found a proper site which allowed the signal to reach its full potential including (coincidentally?) reaching Peterborough.
 

 

August 26, 2022 2:44 pm  #10


Re: "Turn Off the Stereo On FM and See What Happens"

kevjo wrote:

I did hear form someone who was there at the time that when CKLY flipped to FM the owners of the day did it on the super cheap. Instead of a new site, they put the FM stick on the same swampy site. It had worked well for the AM but was not conducive to FM transmission resulting in a signal that didn't get out much past the city limits.
As part of the major technical upgrades they found a proper site which allowed the signal to reach its full potential including (coincidentally?) reaching Peterborough.
 

I do excuse the original owner that made the switch to FM. 
First of all, being a little guy company, not some big guy with deep pockets.
Money wasn't just tight, it was a miracle the station ever managed to stay on the air in the first place.

I seem to recall hearing something like this while tuning in one time way back in the day:
(Before Chum Group took over)

"...and don't forget to thank Joe's Garage, because if it weren't for Joe's Garage, we wouldn't be here!! Thanks for listening to the music of 5 decades..." 


 


RadioWiz & RadioQuiz are NOT the same person. 
RadioWiz & THE Wiz are NOT the same person.

 
 

August 26, 2022 3:51 pm  #11


Re: "Turn Off the Stereo On FM and See What Happens"

Doesn't CRTC mandate some minimum technical standard when granting a license?


You don't have to be a good sport to be a mad one.
 

August 26, 2022 3:55 pm  #12


Re: "Turn Off the Stereo On FM and See What Happens"

kevjo wrote:

I did hear form someone who was there at the time that when CKLY flipped to FM the owners of the day did it on the super cheap. Instead of a new site, they put the FM stick on the same swampy site. It had worked well for the AM but was not conducive to FM transmission resulting in a signal that didn't get out much past the city limits.
As part of the major technical upgrades they found a proper site which allowed the signal to reach its full potential including (coincidentally?) reaching Peterborough.

I was a teen in Omemee at the time, about 10 km LOS from CKLY's site, and the signal, roughly 14 kW ERP, was about as good as what someone in the north end of Lindsay would receive. CKLY-FM actually stayed at the ex-AM site and is still there to this day, but just before the change from "Y92" to "BOB FM" in the mid 2000s, a significantly taller tower was built, allowing CKLY to transmit more efficiently with more height and less power. There were plans a couple of years earlier to move 91.9 to a site in the hills near Bethany, but I believe those were shelved.

I agree with Radiowiz on the ownership group's financial situation... the place had been rather unprofitable for probably the entire time that Centario (a group of area investors) owned CKLY. I can only imagine what it cost for them to a) bring in automation in 1997, and b) set up the FM plant the following year. One jock's job had to be cut, and maybe a second employee as well, shortly before the conversion took place.

 

August 27, 2022 12:30 pm  #13


Re: "Turn Off the Stereo On FM and See What Happens"

A mono FM signal won't activate the receiver's stereo multiplex circuit and will sound quieter as the signal strength drops. With a moderate to low signal when the stereo kicks in there will be an increase in the noise / hiss of the content.

 

August 29, 2022 10:35 am  #14


Re: "Turn Off the Stereo On FM and See What Happens"

Isnt this kind of the same thing as those receivers when you can select stereo to be on/off which we used to push to get rid of the background "hiss"of a weak signal?  

 

August 29, 2022 11:22 am  #15


Re: "Turn Off the Stereo On FM and See What Happens"

There is a theoretical difference in signal-to-noise ratio of 23 dB between stereo and mono. This is due to a number of factors.  The stereo pilot signal at 19 kHz is injected at 9% modulation, so that loss is eliminated.  Also, the required bandwidth for mono reception is significantly less than for stereo.  The stereo difference signal (L-R) is actually a double-sideband suppressed carrier signal centered at 38 kHz, and modulating from 23 to 53 kHz.  Then you have RDS/SCMO subcarriers above this.
CBC's emphasis has always been on wide area regional coverage.  Being mono on Radio 1 means the best possible quality in the fringe areas.
 

 

August 30, 2022 9:26 pm  #16


Re: "Turn Off the Stereo On FM and See What Happens"

markow202 wrote:

Isnt this kind of the same thing as those receivers when you can select stereo to be on/off which we used to push to get rid of the background "hiss"of a weak signal?  

Exactly. When mono is selected (or stereo isn't) the better receivers / tuners will shut off the multiplex circuit in the tuner resulting in less hiss or noise. You will notice the stereo indicator also goes off.

I've seen other (usually cheaper) receivers that don't disable the multiplex and when mono is selected, the noisy stereo signal is sent to the amplifier where it is changed to mono. The result will be a noisy stereo signal that comes out as mono. The FM stereo indicator will stay illuminated.

This can be easily demonstrated if you have a separate tuner and amplifier with a mono selector. Tune to a weak noisy stereo signal and switch the tuner to mono and noise will drop. Put it back on stereo and select mono or L+R on the amp and the noise will not be reduced.

 

September 1, 2022 1:55 pm  #17


Re: "Turn Off the Stereo On FM and See What Happens"

I remember when CKNR AM 1340 Elliot Lake, Ontario with AM transmitters operating at 730 Blind River and 930 Espanola all moved to one FM signal at 94.1 MHz with 90,000 watts in 1997 and the station was mono to start with until Haliburton Broadcasting took over CKNR-FM and switched it to FM stereo with the Moose FM branding in 2004 or '05. The former AM signals in Elliot Lake, Blind River and Espanola were all shutdown after the move to 94.1 FM to cover all of Algoma, Manitoulin and the North Shore including the Sudbury area.

The odd thing is that the high-powered main 94.1 FM transmitter for CKNR-FM Elliot Lake is on Manitoulin Island while they have a low-power 50 watt FM repeater in Elliot Lake (the city of license) operating at 98.7 MHz.

Link to CKNR-FM 94.1:
https://en.m.wikipedia.org/wiki/CKNR-FM

 

October 26, 2022 9:09 am  #18


Re: "Turn Off the Stereo On FM and See What Happens"

Radio World, which originally published the commentary on turning off the stereo on FM to improve reception, has now put out reaction to the article. There's clearly a huge divide among radio professionals about this idea and you can read the wide variety of opinions here

     Thread Starter