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Tighter AM iboc sidebands?

T

Tom Wells

Last weekend both WSCR and WBBM Chicago turned off iboc. 2 days ago, WSCR came back with iboc, now today WBBM is back on with iboc. There was no obvious difference at first, and in extended listening to the host signals, there is nothing new to report as regards the decoded analog of the host. Still has hiss, still critical to center tune, no improvement in "density" or purity of their analog audio.

BUT, when tuning off to the side of WBBM, it seems the sidebands didn't extend as far off to the sides.
So I tuned over to 650 to see how WSM is doing up against WSCRs hash, and I'll be darned if
it doesn't sound like ibiquity pulled the sidebands in a little bit.

COULD be the relative signal levels alone, but I don't think so. Upper side of WSM is still hissed, but center -to-lower sideband
of WSM seems somewhat cleaner, I don't have to tune to the way-lower side of WSM and still hear the hash from WSCR.
Anyone else hear a difference Or have a spectrum analyzer see what this looks like? 'Cuz it sounds narrower.....
 
Sounds to me like "slightly pregnant." Or "a little bit more or less dead."

If it's in my local passband, I don't want it. At ALL. The only acceptable "reduction" is to "zero." Just like the allocations tables call for. Broadcasters have been fined tens of thousands of dollars when their ANALOG signals invade adjacent channels. But when the digital HD signals inflict interference of a magnitude several times worse, it gets ignored by the lawyer-riddled, iBiquity-lobbied FCC.

Politics and special interests win out once again - to the detriment of just about everyone.

Less government, please. Out with the policy nitwits and patronage appointments of non-broadcast industry dummocks.
 
Yes, "slightly pregnant" describes it to a tee, my local WTAG 580 is off today though but of course WBZ is hashing it up like always, like the perennial noise maker it is.
 
Just think... what if the Communists had these IBOC transmitters back in the cold war days? :)
 
Tom Wells said:
Last weekend both WSCR and WBBM Chicago turned off iboc. 2 days ago, WSCR came back with iboc, now today WBBM is back on with iboc. There was no obvious difference at first, and in extended listening to the host signals, there is nothing new to report as regards the decoded analog of the host. Still has hiss, still critical to center tune, no improvement in "density" or purity of their analog audio.

BUT, when tuning off to the side of WBBM, it seems the sidebands didn't extend as far off to the sides.
So I tuned over to 650 to see how WSM is doing up against WSCRs hash, and I'll be darned if
it doesn't sound like ibiquity pulled the sidebands in a little bit.

COULD be the relative signal levels alone, but I don't think so. Upper side of WSM is still hissed, but center -to-lower sideband
of WSM seems somewhat cleaner, I don't have to tune to the way-lower side of WSM and still hear the hash from WSCR.
Anyone else hear a difference Or have a spectrum analyzer see what this looks like? 'Cuz it sounds narrower.....
Click to expand...

Perhaps WBBM is a bit tighter as I have been hearing WABC and WSGW easier now, I'm 17 miles NW of WBBM ("as the crow flies"). It could be that WSCR is a bit narrower with IBOC sidebands (25 miles away in a straight line, so a bit further away for me than WBBM) Certainly not WTMJ or WLW! They're still horribly wide!
 
audioguy said:
Just think... what if the Communists had these IBOC transmitters back in the cold war days? :)
Click to expand...

I bet Cuba would switch to them in a heartbeat if they didn't have to pay iBiquity. Im sure the idea of jamming multiple AM stations with only 1 station's transmitter would sell them on it.
 
audioguy said:
Just think... what if the Communists had these IBOC transmitters back in the cold war days? :)
Click to expand...

Interesting that the jamming transmitters used in those days emitted a combination of both amplitude and frequency modulation, in a way like the COFDM sidebands of IBOC but at a different rate.

On my most recent trip to Berlin, I visited the Post and Telecommunications museum which has an old "Störsender" on display. Here's a photo of a similar unit that was installed in East Berlin in an attempt to jam the western station RIAS - Rundfunk (Broadcasting) im amerikanischen Sektor -- during the Cold War:

http://www.hdg.de/stoersender-rias/

This article (in German) explains how these old transmitters functioned. You can get a fairly good translation to English with Google language tools, or in the Chrome browser:

http://www.radiomuseum.org/forum/stoersender_und_einsprechen.html

Incidentally, RIAS was phased out after the fall of the Berlin Wall, but the former "brand" of its second service RIAS 2 was modified into today's commercial Hot AC station RS2, which transmits with 25 kW on 94.3 from the Alexanderplatz tower in Berlin. It's ironic that this structure (the tallest in Germany) was constructed by the Communist government which never expected that privately-owned stations would someday use it:

http://en.wikipedia.org/wiki/Fernsehturm_Berlin

A few years ago, I recall that RS2 was also available on DAB -- but that feed has been dropped, probably due to lack of interest. However, the Internet stream from the station website is as popular as ever:

http://www.rs2.de/
 
audioguy said:
Just think... what if the Communists had these IBOC transmitters back in the cold war days? :)
Click to expand...

They seem to be more effective as signal jammers than some of the technologies
they were actually using.
 
It's real and for sure. Last night WSM was on long deep fades and I could still listen with a non-directional antenna just fine.
Tonight it was strong and HONKIN'. No problem tuning off just enough to miss the splat 99%.
In the mornings I can now listen to WLW which was utterly lost in the lost WSCR whoosh.

I believe WBBM and WSCR are now operating in compliance with the originally stated AM iboc spec.
It's still not pretty, but at least now it tunes on MY radio exactly the way it was written, as I understood it.

I haven't tried HD decode on them yet.
The audio on both seems improved, they've peaked up the 4khz, and the parasitic rasp on WSCR's analog audio is gone.

It's not time for a party, but I have to give credit to them for making a real change.
If only incremental, implementing this change can alleviate the severity of many instances of noise, or eliminate them all together.

Any station being hissed should be extremely interested in seeing that the " hissor" become upgraded as soon as possible, particularly in the case of a second adjacent hissor.

First adjacent victims are still the gored oxen of honor. :-[
 
Tom said,
It's real and for sure.
Click to expand...

Tom I hope you're right. Have you looked at the signal on a spectrum analyzer? Could it just be propagation effects (bringing up the station receiving interference) making it seem tighter?
 
I have no spectrum analyzer, but have filtered my statements through some time to see what this is.
The car radios of my preference use 262.5 IFs and have pretty steep cutoff skirt response, so when something like this
changes it's pretty easy to tune up and down a little and easily hear the new difference.

The stations still having older setups still have the same old bandwidth "Ponderosa" effect on the same radio.
They seem to have made a reduction in sideband-generated "secondary" images by 6-10 db.
As a result, there seems to be a bit more density in the host analog audio, without haing the sideband image response
reflecting back into the audio passband, and the same reduction in sidebands "beyond the sidebands" which
doesn't help the first adjacents at all, ( it might be even worse for firsts if all that energy is better focused now).
But it does clean things up for the second adjacents.
 
More goings-on... Sat Dec 4 8 AM both stations were back to former "full skirts" bandwidths.
670's whoosh hitting the Espanol in Miwaukee on 640 and hissing even nigh unto the audio sidebands of WGN on 720!

There's not a chance in H E double toothpicks that WLW could be heard through it, so thats a huge difference suddenly.

780's whoosh reaching into the upper audio of WNDZ 750, and extending up to , and into the sidebands of whatever they
call 820 these days.

Checking other adjacent responses WTMJ/WMT etc, found these all unchanged, so the radio's not crazy.

Slept all day so no idea what went on....

Then tonight Sat 10 PM on the way to work, they both seem back to be back in sharp and narrow mode.
There must some testing going on. I really must dig out that Accurian tomorrow. Hope I can find the power supply
as I have been using it for various temporary functions. :D
 
Tom Wells said:
More goings-on... Sat Dec 4 8 AM both stations were back to former "full skirts" bandwidths.
670's whoosh hitting the Espanol in Miwaukee on 640 and hissing even nigh unto the audio sidebands of WGN on 720!

There's not a chance in H E double toothpicks that WLW could be heard through it, so thats a huge difference suddenly.

780's whoosh reaching into the upper audio of WNDZ 750, and extending up to , and into the sidebands of whatever they
call 820 these days.

Checking other adjacent responses WTMJ/WMT etc, found these all unchanged, so the radio's not crazy.

Slept all day so no idea what went on....

Then tonight Sat 10 PM on the way to work, they both seem back to be back in sharp and narrow mode.
There must some testing going on. I really must dig out that Accurian tomorrow. Hope I can find the power supply
as I have been using it for various temporary functions. :D
Click to expand...

My local WTAG 580 has been off and on several times for week long periods lately but there very wide when on, luckily for MA there are off at night. I do know they tested the whoosh maker at night for several days and found it unworkable probably because of their wide sidebands, I heard somewhere they may have had antenna problems with the iBlock also.
 
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