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WEBE 108 HD Signal Observations

N

nd2023

Banned
I was going west on I95 today coming from Providence, RI, and going back home before the big snowstorm hit. I noticed that WEBE 108's IBOC hash was stronger west of the smokestack tower than east of it. While approaching WEBE from the east, the analog signal drowned out the IBOC hash when it was overloading. While going west away from the tower, the HD signal was very strong, and the IBOC hash even interfered with the analog signal. I also noticed that at a distance of 15 miles from WEBE's tower, the IBOC hash was more audible 15 miles west of the tower than 15 miles east. Is there an explanation for this? Is it done intentionally to lessen interference with Jammin' 107.7, or is it unintentional?<P ID="signature">______________
17-year-old radio geek
Location: Princeton Junction, NJ
AIM: KewlDude471
WWPH 107.9 FM: http://wwph1079fm.no-ip.org</P>
 
Are there second-adjacent issues with WBLS-FM 107.5 of New York City at all?<P ID="signature">______________
The 2006 New York Yankees...on to title #27!</P>
 
I know up at okemo and stratton I get kiss108 and not webe on my walkman on top of the mountain this weekend.
I can't wait t give my sangean a try when I get it in the mail this week...
you could have gotten a great dx due to the weather.
there was a lot of electrical energy in this storm.
(depending on where you were last night there was heavy thundersnow)
I noticed on my way from stratton on sat down to drop off a freind in benington VT and then passed bromly to okemo in ludlow sat night I was getting great radio out of boston and albany clearer than normal (depending on where I was and the terrain)
my question for you is when you come from boston to nyc where do you get the split of webe 108 and kiss 108 fm?

~OZ 91.5
myspace.com/theozno


> I was going west on I95 today coming from Providence, RI,
> and going back home before the big snowstorm hit. I noticed
> that WEBE 108's IBOC hash was stronger west of the
> smokestack tower than east of it. While approaching WEBE
> from the east, the analog signal drowned out the IBOC hash
> when it was overloading. While going west away from the
> tower, the HD signal was very strong, and the IBOC hash even
> interfered with the analog signal. I also noticed that at a
> distance of 15 miles from WEBE's tower, the IBOC hash was
> more audible 15 miles west of the tower than 15 miles east.
> Is there an explanation for this? Is it done intentionally
> to lessen interference with Jammin' 107.7, or is it
> unintentional?
>
 
> I was going west on I95 today coming from Providence, RI,
> and going back home before the big snowstorm hit. I noticed
> that WEBE 108's IBOC hash was stronger west of the
> smokestack tower than east of it. While approaching WEBE
> from the east, the analog signal drowned out the IBOC hash
> when it was overloading. While going west away from the
> tower, the HD signal was very strong, and the IBOC hash even
> interfered with the analog signal. I also noticed that at a
> distance of 15 miles from WEBE's tower, the IBOC hash was
> more audible 15 miles west of the tower than 15 miles east.
> Is there an explanation for this? Is it done intentionally
> to lessen interference with Jammin' 107.7, or is it
> unintentional?
>
For stations broadcasting on 107.9 FM using IBOC, isn't some of the hash going onto 108.1 FM, past the end of the FM band? Is any special clearance needed from the FCC for that?
 
> > Is there an explanation for this? Is it done
> intentionally
> > to lessen interference with Jammin' 107.7, or is it
> > unintentional?
> >

The IBOC carriers are supposed to be -20dB (100 times) below the analog carrier. Due to the same things that cause analog reception to be so variable, that ratio can change. Multipath, other interfering stations, atmospheric conditions, equipment failure...all things that can cause that -20dB ratio to get out of whack. Although admittedly under normal circumstances it isn't SUPPOSED to happen so it's possible there's something wrong with the WEBE facility.


> For stations broadcasting on 107.9 FM using IBOC, isn't some
> of the hash going onto 108.1 FM, past the end of the FM
> band? Is any special clearance needed from the FCC for
> that?
>

Just to nitpick...108.1MHz is not the end of the band. 108.0 is. All stations have a 200kHz channel, so naturally the center of the channel is where the analog carrier is strongest. Ergo, "107.9" is really 107.8 to 108.0MHz.

Regardless, the answer to your question is "no, no special clearance is needed" because there is no interfering signal...not unless something in their IBOC facility is malfunctioning, anyway. All IBOC transmissions are required to meet the spectral mask which prevents interference from channel to channel...even on the edges of the band.

That's not to say that a radio tuned to 108.1MHz won't hear IBOC white noise...although even that would be heavily dependent on the quality of the radio and antenna. For example, I can turn off the SHARX I.F. filter on my Blaupunkt car stereo and IBOC white noise does a number on 1st-adjacent stations I wish to listen to...but with the filter on, the white noise mostly goes away.
 
> Regardless, the answer to your question is "no, no special
> clearance is needed" because there is no interfering
> signal...not unless something in their IBOC facility is
> malfunctioning, anyway. All IBOC transmissions are required
> to meet the spectral mask which prevents interference from
> channel to channel...even on the edges of the band.

I don't know whether there's harmful interference above 108MHz, but there certainly is signal up there! Note the spectrum analyzer photos on http://users.tns.net/~bb/iboc.htm and the official IBOC specification on
http://www.ibiquity.com/technology/pdf/Waveforms_FM.pdf. The IBOC sidebands spread out to just shy of 200KHz either side of center channel.

Since the stations above 108MHz aren't FM broadcasters, I don't know exactly how they'll respond to IBOC interference. I suspect for self-preservation they've already avoided putting anything particularly sensitive too low in the 108-136MHz band! Still, it's surprising that a FCC that's been very sensitive to other potential sources of interference to airnav hasn't said anything about this...

> That's not to say that a radio tuned to 108.1MHz won't hear
> IBOC white noise...although even that would be heavily
> dependent on the quality of the radio and antenna.

Well, the IF filter would have to pass less than 2KHz below carrier to avoid the digital altogether, at which point it would make a pretty awful FM radio<grin>!
 
> I know up at okemo and stratton I get kiss108 and not webe
> on my walkman on top of the mountain this weekend.
> I can't wait t give my sangean a try when I get it in the
> mail this week...
> you could have gotten a great dx due to the weather.
> there was a lot of electrical energy in this storm.
> (depending on where you were last night there was heavy
> thundersnow)
> I noticed on my way from stratton on sat down to drop off a
> freind in benington VT and then passed bromly to okemo in
> ludlow sat night I was getting great radio out of boston and
> albany clearer than normal (depending on where I was and the
> terrain)
> my question for you is when you come from boston to nyc
> where do you get the split of webe 108 and kiss 108 fm?
>
> ~OZ 91.5
> myspace.com/theozno
>
>
> > I was going west on I95 today coming from Providence, RI,
> > and going back home before the big snowstorm hit. I
> noticed
> > that WEBE 108's IBOC hash was stronger west of the
> > smokestack tower than east of it. While approaching WEBE
> > from the east, the analog signal drowned out the IBOC hash
>
> > when it was overloading. While going west away from the
> > tower, the HD signal was very strong, and the IBOC hash
> even
> > interfered with the analog signal. I also noticed that at
> a
> > distance of 15 miles from WEBE's tower, the IBOC hash was
> > more audible 15 miles west of the tower than 15 miles
> east.
> > Is there an explanation for this? Is it done
> intentionally
> > to lessen interference with Jammin' 107.7, or is it
> > unintentional?
> >
>
WEBE 108 gets interference from Jammin' 107.7, and then Kiss 108 comes in when Jammin' 107.7 weakens in Rhode Island.<P ID="signature">______________
17-year-old radio geek
Location: Princeton Junction, NJ
AIM: KewlDude471
WWPH 107.9 FM: http://wwph1079fm.no-ip.org</P>
 
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