Late Night Radio: Fading, Flutter and...?

[Todd, KA1KAQ]

Not sure that this question would qualify for the tech board, so...

Late one night in the recent past, I got the urge to fire up the old Zenith shutterdial for a little AM radio listening. Listened to a couple of ball games on WFAN and another station out of Philly. Last night I tuned into 740 AM out of Toronto, playing oldies.

I'm familiar with the typical signal drops due to fading, also the flutter often heard on signals. But what is the correct term for the distortion/overload when the signal builds back up and comes rushing in? Seems I knew this at one time, damned if I can remember now.

Also curious to know the station someone mentioned in Canada that plays Big Band music? Maybe the same 740? Listened for over an hour last night and never heard their callsign. Sure do miss good ol' WOWO from Jack's area, Fort Wayne.

[k4kyv]

I'm familiar with the typical signal drops due to fading, also the flutter often heard on signals. But what is the correct term for the distortion/overload when the signal builds back up and comes rushing in? Seems I knew this at one time, damned if I can remember now.

Selective fading.

[W1GFH]

But what is the correct term for the distortion/overload when the signal builds back up and comes rushing in?

Do you have distortion and overload on strapping local signals also? Sounds like an AVC problem. If not, maybe you are talking about a skywave signal being rec'd together with a ground wave component which is out of phase.

[Todd, KA1KAQ]

Joe, local signals are strong, but not distorted. This is more of a 'to and fro' situation where the band is unsettled and the stations fade out, sometimes down to being barely heard, then build back in to the point of overload, then back down to average, 'normal' audio.

I bet you're on the money about multi-path/out of phase. Don suggests selective fading, which is interestingling similar in description. From Wikipedia:

Selective fading or frequency selective fading is a radio propagation anomaly caused by partial cancellation of a radio signal by itself — the signal arrives at the receiver by two different paths, and at least one of the paths is changing (lengthening or shortening). This typically happens in the early evening or early morning as the various layers in the ionosphere move, separate, and combine. The two paths can both be skywave or one be groundwave.

Selective fading manifests as a slow, cyclic disturbance; the cancellation effect, or "null", is deepest at one particular frequency, which changes constantly, sweeping through the received audio.

The effect can be counteracted by applying some diversity scheme, for example OFDM modulation, or by using two receivers with separate antennas spaced a quarter-wavelength apart, or a specially-designed diversity receiver with two antennas. Such a receiver continuously compares the signals arriving at the two antennas and presents the better signal.

It doesn't specifically address the overload component which, to me seems like the opposite of fading. Otherwise the description is right on the mark.

BTW, AM 740 out of Toronto had Big Band music on last night, so I think I may have answered my own question there.

[Ralph W3GL]

Todd,


" C K W O"

740 AM... Toronto...

Ralph

[Bacon, WA3WDR]

Why did the station on 740 from Toronto change callsigns?  Back in the 60s they were CBL, then they just called themselves CBC, and now it's something else.

[ve6pg]

...the cbc has sold off alot of it's mw transmitting sites. they have gone to the fm band, and have two types of programs. cbc1, and cbc2.
 at the transmitter site, the old cbl transmitter, antennas, etc are now owned by the group that is am740. at the same site are the antennas and transmitter for cjbc, 860,cbc radio canada french network.
 before the move to 740, the station was located in oakville, west of toronto, abt 20 miles. as i recall, that station had the same call, but was in the graveyard, around 1400kc....sk..

[k4kyv]

I can remember in the 60's listening to CJBC 860 on the car radio.  I  had it on one of the mechanical presets, along with WLS in Chicago.  Now, I can rarely hear CJBC on any AM radio, because all the power line noise and the little toy radio stations all over the country that the FCC allowed to operate post-sunset completely obliterate them, and WLS is nothing but a bunch of talk radio windbags spouting political propaganda.

I can still get CJBC via streaming audio on the computer, and the audio quality is better than I ever could get on the AM broadcast band, but somehow the magic is not there.

On the AMBC band the "fading wall" occurs where the groundwave is attenuated just to the point that the skywave begins to interfere, and most of the time the signal sounds like slopbucket on a diode detector.  That is what defines the outer limit of useful nighttime coverage, called the "primary" coverage contour.  With what's left of the clear channel stations, you may get a solid skywave signal a few hundred miles out, in what is called the "secondary" coverage area.  The gap between the beginning of the fading wall and the secondary coverage area is called the "skip zone".

The same phenomenon may occur on 160m.

[KI4VEO]

I was listening to 740 around 4am this past Sunday morning on my way home.  I too noticed the "fluttering" just as they were giving their callsign.  I had to wait until the next ID to find out who they were.

As I was driving along I could hear the fade, and then it picked up rather quickly - almost as if it was because I was driving through one wave front to the next, which I was, to some extent.  No distortion...just down almost into the noise floor, and then back up like a local.

BTW - I am about 25 miles SW of Washington, D.C.

Just my 2 cents....

[flintstone mop]

You can thank some urban hokey station in New York for silencing WOWO or reducing the nighttime to 10KW directional (I think)
fred

[KI4VEO]

I miss, "The BIG 8,"  CKLW.

Now THAT was a station !

[k4kyv]

You can thank some urban hokey station in New York for silencing WOWO or reducing the nighttime to 10KW directional (I think)
fred

The corporation that owns that hokey station in New York (maybe ClearChannel but I'm not positive), bought WOWO specifically for the purpose of reducing its coverage area to avoid interfering with the New York station, which the FCC had just allowed to go from daytime-only to full time.

One of the things that has about killed the AMBC band is that too many radio stations are licensed.  Almost every little one-horse town with population of no more than 5000 people has one or two local radio stations.  There simply isn't enough advertising revenue to go around, so they just barely break even, even if that, while they pay their employees just a little over minimum wage.  To save money, they subscribe to satellite feeds to avoid hiring real announcers and PD's.  The result is that the band is jam packed with signals on every channel and only the 50 kw blowtorches have any chance of getting out beyond the city limits at night.  And the stations you can hear are 90% talk radio, with a bunch of windbags screaming out the same old bogus political propaganda night after night.  No wonder most people now listen only to FM. 

I asked a group of about 25 high school kids a few months ago to show their hands if they ever listened to AM radio.  Not a single kid raised his or her hand.  Then I asked how many  listened to FM.  Nearly all raised their hand.  About a half dozen indicated that they listened to streaming audio over the internet or listened to satellite radio.  Maybe a third of  the group said they listened to iPods.

My conclusion:  most kids still listen to the radio, but hardly anyone ever listens to AM, and the majority don't regularly listen to iPod, satellite or streaming audio.

Almost comically, AM broadcasters are now lobbying the FCC to allow them to  run FM translators to fill in the holes in their coverage area.  They call this a plan to "save" AM radio.  If the translators are on FM, they are NOT running AM, so what is that, other than a partial conversion to FM?  Once listeners become accustomed to hearing the FM translator at night when the AM signal fades out, are they really going to switch back to the primary AM frequency during daylight hours?

[Steve - WB3HUZ]

WOWO is owned by Federated Media, not Clear Channel.

http://www.federatedmedia.com/

[Sam KS2AM]

I miss, "The BIG 8,"  CKLW.

CKLW is still there but I think its the old format you miss and not the syndicated talk shows that they run now.  Me too.

But I really miss the 500 KW Transworld Radio signal on 800 kc from Bonaire that would occasionally strap CKLW during the evenings ... on my car radio ... or walkman.





http://www.fybush.com/sites/2006/site-060526.html


Sam

[ve6pg]

..interesting topic...i remember PJB, Bonaire...but i thought there was enough interest in the mw band, and that is why it was expanded to 1700kc, and down to 530kc....they should really rethink the mess that is approx. 1300-1500kc...too many low powered stations, creating a real mess at night....sk..

[K3ZS]

AM 740 is one of my favorite stations, not overblown with commercials, with good old buzzard music.    When the radio can't pick it up you can listen live at www.am740.ca.

[Todd, KA1KAQ]

" C K W O"

740 AM... Toronto...

Thanks, Ralph -

Of course, I finally caught their callsign last Thursday or Friday night. One night this weekend they were playing 70s disco-sounding music, so after tuning around and finding not much else, I switched to one of the shortwave bands. Radio Ukraine was booming in until midnight, when they left the air. They were reading viewer reports for QSL cards, complete with the thick accents reminiscent of the Radio Moscow/Cold War days. What a hoot!

WQEW in NY used to play Big Band music exclusively. They were bought out by Disney and now play kid's music. WCRN in the Worcestor/Framingham Mass area also played Big Band and 'American Standards' like Sinatra etc. They changed to a Moldy Oldies format a year or so back. I guess they figure the folks who like Big Band are getting scarce, so it's time to program for the next generation of Fudds?