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Why aren't stations allowed to broadcast a higher-powered HD signal?

J

JM_pstar

Guest
In cases where the HD signal might not cover all of a station's coverage area, why are they not allowed to increase the station's HD power? When HD Radio becomes more common or all stations broadcast in HD, might this change?

-JM<P ID="signature">______________
16-year-old radio geek.</P>
 
> In cases where the HD signal might not cover all of a
> station's coverage area, why are they not allowed to
> increase the station's HD power? When HD Radio becomes more
> common or all stations broadcast in HD, might this change?
>
> -JM

I've been curious myself. I figured the lower power was in some way an admission that the IBOC sidebands would interfere too much with adjacent channels if they were cranked up to full power.

But once HD Radio stations shut off the analog - surely they would then be allowed to broadcast a digital stream at full power (since they would be relocating it to the center of their assigned frequency)?
 
> In cases where the HD signal might not cover all of a
> station's coverage area, why are they not allowed to
> increase the station's HD power? When HD Radio becomes more
> common or all stations broadcast in HD, might this change?

Here’s the answer

iBiquity Digital’s HD Radio system specifications call for the transmission of digital carriers at a combined power of -20 dB relative to the total power output of the analog signal. This equates to a relative digital power of one percent of the analog power. This value was selected to minimize digital-to-analog interference while maximizing the coverage of the digital signal. Thus, a station broadcasting with 10 kW of analog power need only transmit 100 watts of digital power to cover a similar area.

<a target="_blank" href=http://www.broadcastpapers.com/ibc2004/IBC04iBiguityIBOC03.htm>http://www.broadcastpapers.com/ibc2004/IBC04iBiguityIBOC03.htm</a>
 
Because

there are no receivers to hear it...
Sorry, was just to easy. I even slept on it and still had to post. LOL
 
You are partially right

The digital signal is almost completely on the adjacent frequency. There are already interference problems now that cause harmful interference to the neighbors station. Notice AM cannot use digital at nite for that reason. The only was digital power will increase is when analog goes away. Dont hold your breath for that....Your grandkids will have assumed room temp before that will ever happen.
 
Re: You are partially right

> ...when analog goes away. Dont
> hold your breath for that...

Exactly.

HD Radio is not mandatory. There will probably be some radio stations that won’t convert to HD, due to the expense and / or other reasons.
 
> iBiquity Digital’s HD Radio system specifications call for
> the transmission of digital carriers at a combined power of
> -20 dB relative to the total power output of the analog
> signal. This equates to a relative digital power of one
> percent of the analog power. This value was selected to
> minimize digital-to-analog interference while maximizing the
> coverage of the digital signal. Thus, a station broadcasting
> with 10 kW of analog power need only transmit 100 watts of
> digital power to cover a similar area.

Hmm. When I had my loaner IBUZ receiver there wasn't a single station that had a digital signal that covered the same area as the analog. The receiver switched out of digital well before the analog signal became noisy enough to be annoying.

Real life doesn't seem to agree with the specs.

Rich
 
Re: You are partially right

I wonder if any near-border FM (or AM) stations have been prevented from running IBUZ by complaints from the CRTC (Canada) of adjacent channel interference.
<P ID="signature">______________
Proud 2 B a pioneering satellite radio subs¢riber
Ai4i is always on the trailing edge of technology
______________</P>
 
> > iBiquity Digital’s HD Radio system specifications call for
>
> > the transmission of digital carriers at a combined power
> of
> > -20 dB relative to the total power output of the analog
> > signal. This equates to a relative digital power of one
> > percent of the analog power. This value was selected to
> > minimize digital-to-analog interference while maximizing
> the
> > coverage of the digital signal. Thus, a station
> broadcasting
> > with 10 kW of analog power need only transmit 100 watts of
>
> > digital power to cover a similar area.
>
> Hmm. When I had my loaner IBUZ receiver there wasn't a
> single station that had a digital signal that covered the
> same area as the analog. The receiver switched out of
> digital well before the analog signal became noisy enough to
> be annoying.
>
> Real life doesn't seem to agree with the specs.
>
> Rich

The key word here is "similar"... It's not going to be "exactly identical".
 
> > Hmm. When I had my loaner IBUZ receiver there wasn't a
> > single station that had a digital signal that covered the
> > same area as the analog. The receiver switched out of
> > digital well before the analog signal became noisy enough
> > to be annoying.
> >
> > Real life doesn't seem to agree with the specs.

> The key word here is "similar"... It's not going to be
> "exactly identical".

The FM digital reverted to analog between 7-10 miles before the analog became annoying in nearly every case. This was in Boston, Worcester, MA, Springfield, MA, Hartford, CT and Albany, NY.

I can receive WBZ in Springfield, MA. I lost its digital at about Worcester, MA, easily 40 miles from Springfield on the Mass Turnpike. At the lookout tower on the Mt. Tom reservation WBZ's digital would come back at various points.

Rich
 
Re: You are partially right

> I wonder if any near-border FM (or AM) stations have been
> prevented from running IBUZ by complaints from the CRTC
> (Canada) of adjacent channel interference.

I recall that Canada filed a complaint a while back. Since Canada doesn't have the bomb, I think they were ignored.

Rich
 
> > > Hmm. When I had my loaner IBUZ receiver there wasn't a
> > > single station that had a digital signal that covered
> the
> > > same area as the analog. The receiver switched out of
> > > digital well before the analog signal became noisy
> enough
> > > to be annoying.
> > >
> > > Real life doesn't seem to agree with the specs.
>
> > The key word here is "similar"... It's not going to be
> > "exactly identical".
>
> The FM digital reverted to analog between 7-10 miles before
> the analog became annoying in nearly every case. This was in
> Boston, Worcester, MA, Springfield, MA, Hartford, CT and
> Albany, NY.
>
> I can receive WBZ in Springfield, MA. I lost its digital at
> about Worcester, MA, easily 40 miles from Springfield on the
> Mass Turnpike. At the lookout tower on the Mt. Tom
> reservation WBZ's digital would come back at various points.
>
>
> Rich
>

My experience is far different!

For example, Chicagos WJMK which runs 4.1kW at 480M (which means that the HD signal is just 41 watts at 480M), I can receive from Kenosha, WI (60 kiles or so) was pretty much solid. I held the WJMK HD2 signal until I got the the Indiana/Michigan state line (sorry I dont know the distance). It gave me over 2 hours of listening time driving through Chicago.

In regards to AM, I am presently in Lafayette, IN and was picking up WSCR 670 in HD. Thats a distance of about 110 miles.

Scott Fybush was getting the WBZ HD ID in Syracuse (265 miles) but was not switching over to the digital signal.

I have found the switch from digital to analog to be quite smooth.

Rich perhaps you need to check your antenna.

My equipment is the Kenwood with the stock Ford Expedition antenna. Nothing fancy.
 
Re: You are partially right

> > I wonder if any near-border FM (or AM) stations have been
> > prevented from running IBUZ by complaints from the CRTC
> > (Canada) of adjacent channel interference.
>
> I recall that Canada filed a complaint a while back. Since
> Canada doesn't have the bomb, I think they were ignored.
>
> Rich
>


I beleive the discussion was about AM HD.

When I first turned on one of my HD FM stations, no one noticed any additional noise from the HD signal. I had to tell the local DXers that I had the signal on, they didnt realize it was on.
 
Re: You are partially right

> When I first turned on one of my HD FM stations, no one
> noticed any additional noise from the HD signal. I had to
> tell the local DXers that I had the signal on, they didnt
> realize it was on.

Here in the Northeast where there are adjacent channels from adjacent markets all over the place and any good car radio can pick up a listenable signal on nearly FM frequency, believe me, we CAN hear the difference when a station's hash generator is on and turns the adjacent channels to hisssss.

Just ask the NYC FM stations why their ratings in Trenton, NJ are going down the tubes -- it's because of IBUZ interference from neighboring Philly signals, which has turned their formerly clean-and-clear stereo signals into barely listenable hissy mono signals.
<P ID="signature">______________
It's a common mistake to not use punctuation in its proper form.
<a target="_blank" href=http://www.cgl.uwaterloo.ca/~csk/its.html>Be kind to your friend, the apostrophe.</a></P>
 
> My experience is far different!
>
> For example, Chicagos WJMK which runs 4.1kW at 480M (which
> means that the HD signal is just 41 watts at 480M), I can
> receive from Kenosha, WI (60 kiles or so) was pretty much
> solid. I held the WJMK HD2 signal until I got the the
> Indiana/Michigan state line (sorry I dont know the
> distance). It gave me over 2 hours of listening time driving
> through Chicago.
>
> In regards to AM, I am presently in Lafayette, IN and was
> picking up WSCR 670 in HD. Thats a distance of about 110
> miles.
>
> Scott Fybush was getting the WBZ HD ID in Syracuse (265
> miles) but was not switching over to the digital signal.
>
> I have found the switch from digital to analog to be quite
> smooth.
>
> Rich perhaps you need to check your antenna.
>
> My equipment is the Kenwood with the stock Ford Expedition
> antenna. Nothing fancy.

My antenna was a mag mount supplied by Kenwood mounted on the center of the roof. Kenwood loaned me a tuner and controller.

Analog reception with this setup was terrific, so I doubt I had any antenna problem. Stations appeared that I'm unable to receive with any other receiver I own. I'd buy the Kenwood if it were less expensive based on its analog performance, alone. Essentially, we're using the same equipment. My antenna might even have been better. As recommended by Kenwood, the tuner was physically grounded to the car body to enable the AM reception the tuner is capable of.

It appears that terrain is an issue. I'm in mountainous New England. Western MA, to be exact.

I'm about 125 miles from WBZ's antenna. I always got an HD indication. I'm about the same distance from WOR in air miles. I didn't get an HD signal, though the tuner indicated HD. I get a moderately listenable signal in analog from WOR even though I have a station (once owned by George Poppele - Telemeasurements) at 730. I worked there as a kid. Monster 5Kw signal from a riverside site in Chicopee, MA.

With the exception of analog vs. digital coverage, our experiences appear to be very similar. When stations begin to process separately we'll have a better handle on how listeners will handle mode switching.

During the time I had the receiver the area's only HD2 signal was off the air due to HD technical problems. I was unable to do any traveling to test secondaries. I returned the equipment a day after their HD2 came back. The engineer hadn't had time to adjust processing, so I don't feel it's fair to comment on the HD2 quality.

In this case, our mileage does vary.

Rich
 
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