HD Radio signal question

[Oscar]

I read the story on rwonline.com about the quality of music on AM radio with HD. But, does the signal improve?

If you have a small 500 or 1000 watt station with a bad signal in analog, is the signal just as bad in digital? Will HD help to increase range at all?

Thanks!

 

[Chuck]

> I read the story on rwonline.com about the quality of music
> on AM radio with HD. But, does the signal improve?
>
> If you have a small 500 or 1000 watt station with a bad
> signal in analog, is the signal just as bad in digital?
> Will HD help to increase range at all?

No, as I understand it, the signal strenght will be about the same, or even less with the Ibiquity digital scheme. When you get to the edge of the digital signal, the radio is supposed to "blend" back to analog.

At last week's Texas Association of Broadcasters Convention, there were several seminars about the transition, from people in the trenches of digital radio. It seems that not everything is going well.

One presenter was the owner of a pair of small AM stations that has recently adopted the Kahn digital system. It can run at night, and does not produce interfering sidebands with your near adjacent neighbors. This was a big deal to them, because their sister station would be the one getting the interference!

The GM/owner reported that adopting this system radically improved their analog coverage, as well as frequency response. His conclusion was that it was worth the investment to get the improvement in his analog AM and if anyone ever buys a receiver that could decode the digital part, that was icing on the cake.


YMMV

 

[tpt]

A digital signal should be more immune to environmental noise, so inside the normal coverage area (let's say the 1 mv for an example) the signal will be much cleared in those areas now subject to electrical noise.

On the other hand, if an adjacent channel station lights up an IBOC signal it's not clear how much effect this will have on the coverage of either station.

 

[Len14043]

> A digital signal should be more immune to environmental
> noise, so inside the normal coverage area (let's say the 1
> mv for an example) the signal will be much cleared in those
> areas now subject to electrical noise.
WLW ran IBOC tests in 2003. The digital signal blended to analog at signal strenghts ranging from 2.5 to 6.3 mv/m, about 100 and 50 miles from their tower, respectively. The digital should be much better in the all digital mode - if we ever get there!

> On the other hand, if an adjacent channel station lights up
> an IBOC signal it's not clear how much effect this will have
> on the coverage of either station.
I'm curious how well hybrid IBOC will work at night. For instance, WOR's digital reportedly works fine during the day. However, what will happen to their digital signal at night when the skywave from WLW and WGN occasionally muscles in on 700 and 720. Will the receiver be able to descriminate between WOR's digital hash and the analog audio on 700 and 720?!

 

[CW]

> One presenter was the owner of a pair of small AM stations
> that has recently adopted the Kahn digital system. It can
> run at night, and does not produce interfering sidebands
> with your near adjacent neighbors. This was a big deal to
> them, because their sister station would be the one getting
> the interference!
>
> The GM/owner reported that adopting this system radically
> improved their analog coverage, as well as frequency
> response. His conclusion was that it was worth the
> investment to get the improvement in his analog AM and if
> anyone ever buys a receiver that could decode the digital
> part, that was icing on the cake.

This presenter would be Ralph Mcbride, right?? KOLE and KRCM in the Golden Triangle are the stations in question....1380 (KRCM)'s audio sometimes is highly distorted and clipped....1340 (KOLE)'s is not bad.......but WHO has KAHN Cam-D receivers? (NOONE!) I have NOT personally seen a "radical" improvement on either signal, much less ANY improvement....and I travel SE TX and SW LA quite a bit and tune the AM band on a regular basis....Cam-D uses the same basic equipment as Powerside and Kahn's ISB AM stereo system...but Leonard Kahn refuses to give out any technical details on his system or license receivers (which is why his ISB Stereo system died....NOONE could build a rcvr to work on his system well)...

IBOC is a true digital system....Cam-D is a hybrid.....the analog carrier is used in the L+R audio....but noone really knows WHAT the digital does since Kahn doesnt give out details....but IBOC is a debacle itself....and it cannot be used at night (yet and I hope it never is!)

 

[k9ez]

> I read the story on rwonline.com about the quality of music
> on AM radio with HD. But, does the signal improve?
>
> If you have a small 500 or 1000 watt station with a bad
> signal in analog, is the signal just as bad in digital?
> Will HD help to increase range at all?
>
> Thanks!
>


I have an HD receiver. I have found that the HD indicator will light in some marginal areas, but the receiver will not kick over to digital until the signal gets stronger. Basically any areas that have some noise for analog probably will not have digital coverage.

Yes the HD receiver does a nice job at fading from digital to analog, but the difference in audio quality is quite marked and it is a surpise when it fades back to analog.

I have been TOLD that for directional stations, that HD will help increase coverage in the nulls. The two AM HD stations I have in the area are omni, so I dont have first hand knowledge.

 

[w9wi]

> details on his system or license receivers (which is why his
> ISB Stereo system died....NOONE could build a rcvr to work
> on his system well)...

The construction of an ISB receiver is no huge secret. (heck, one could get noticable stereo separation by simply using two regular radios, carefully tuned...)

 

[tpt]

> I have been TOLD that for directional stations, that HD will
> help increase coverage in the nulls. The two AM HD stations
> I have in the area are omni, so I dont have first hand
> knowledge.
>

Saw a presentation by one of Iniquity's shills on this very point. He used the example of WWJ's (950--Detroit) coverage of Toledo as his example. WWJ used to be 5 kw, with a transmitter site north of downtown Detroit. Now they use a comnplex array to saturate Detroit and the northern suburbs with 50 kw. The pattern must protect a daytime station on 940 in Lima, Ohio, some 100 miles to the south. Hence, there is very little signal over Toledo, which is maybe 20 miles off the back of the array. IBOC, claimed the Iniquity spokesman, fills in these nulls (as he flashed a map showing test results of the IBOC signal reception in the deep nulls over Toledo).

What this Iniquity clown didn't understand is this coverage was obtained at the price of interference to this daytimer. As anyone with a DA knows, the pattern +/-10 kc off the carrier frequency can be different than on carrier. The lower the frequency, the more complex the array, the more pronounced departures from the modeled pattern.

So, for WWJ, at the point where their signal hit the protected daytime .5 of the Lima station (near Findlay, Ohio), the 950 signal was just a whisper. As the designers of the array intended. On 940, however, the 950 IBAC sidebands completely covered the 940 signal from Lima.

But, as this Iniquity spokesman stated, we all must make sacrifices for digital radio. It seems, though, that it's the other stations that must sacrifice.

 

[Chuck]

> This presenter would be Ralph Mcbride, right?? KOLE and KRCM
> in the Golden Triangle are the stations in question....1380
> (KRCM)'s audio sometimes is highly distorted and
> clipped....1340 (KOLE)'s is not bad.......but WHO has KAHN
> Cam-D receivers? (NOONE!) I have NOT personally seen a
> "radical" improvement on either signal, much less ANY
> improvement....and I travel SE TX and SW LA quite a bit and
> tune the AM band on a regular basis....

Yes, it was. I hope I accurately reported what he said.


Cam-D uses the same
> basic equipment as Powerside and Kahn's ISB AM stereo
> system...but Leonard Kahn refuses to give out any technical
> details on his system or license receivers (which is why his
> ISB Stereo system died....NOONE could build a rcvr to work
> on his system well)...
>

Not telling people what you have to do to receive the signal is a huge problem. It seems Leonard Kahn has had PR problems in the past which continue today. Some folks report that these problems are self inflicted on Mr. Kahn's part. Maybe so. I've never met the man.

> IBOC is a true digital system....Cam-D is a hybrid.....the
> analog carrier is used in the L+R audio....but noone really
> knows WHAT the digital does since Kahn doesnt give out
> details....but IBOC is a debacle itself....and it cannot be
> used at night (yet and I hope it never is!)

Yes, as I understand it, you are listening to a "baseband" analog signal, with the high frequency part derived by some digital means. If that is indeed true, it would indicate to me that the signal would still be susceptable to outside interference, much like AM is right now.

On the other hand, IBOC does not look like a good idea to me, either on AM of FM, because of the sidebands it generates. I can see how it would work very nicely in some areas, but in many parts of the US, the FM band is as crowded as the AM side can be at night. There is going to be interference. The only way I can see it working at night on AM, would involve turning off about 2/3 of the existing stations at night. Likewise, it would work better in the daytime if about half the stations went away. Maybe that's what the backers of IBOC have in mind.

DRM, anybody?

 

[k9ez]

> > I have been TOLD that for directional stations, that HD
> will
> > help increase coverage in the nulls. The two AM HD
> stations
> > I have in the area are omni, so I dont have first hand
> > knowledge.
> >
>
> Saw a presentation by one of Iniquity's shills on this very
> point. He used the example of WWJ's (950--Detroit)
> coverage of Toledo as his example. WWJ used to be 5 kw,
> with a transmitter site north of downtown Detroit. Now they
> use a comnplex array to saturate Detroit and the northern
> suburbs with 50 kw. The pattern must protect a daytime
> station on 940 in Lima, Ohio, some 100 miles to the south.
> Hence, there is very little signal over Toledo, which is
> maybe 20 miles off the back of the array. IBOC, claimed the
> Iniquity spokesman, fills in these nulls (as he flashed a
> map showing test results of the IBOC signal reception in the
> deep nulls over Toledo).
>
> What this Iniquity clown didn't understand is this coverage
> was obtained at the price of interference to this daytimer.
> As anyone with a DA knows, the pattern +/-10 kc off the
> carrier frequency can be different than on carrier. The
> lower the frequency, the more complex the array, the more
> pronounced departures from the modeled pattern.
>
> So, for WWJ, at the point where their signal hit the
> protected daytime .5 of the Lima station (near Findlay,
> Ohio), the 950 signal was just a whisper. As the designers
> of the array intended. On 940, however, the 950 IBAC
> sidebands completely covered the 940 signal from Lima.
>
> But, as this Iniquity spokesman stated, we all must make
> sacrifices for digital radio. It seems, though, that it's
> the other stations that must sacrifice.
>


No argument from me.

It seems that the arrays of the past are really going to need a good look over if they are going to be useful for HD.

BTW has anyone seen the 950 array?? Looks like a bunch of towers sprinkled about willy nilly. LOL

 

[pianoplayer88key]

Here's some of my criteria for a digital AM transmitting system that's used on the 510 to 1715 kHz band:

NO AUDIBLE HASH ON SIDEBANDS ON ANALOG RADIOS, EVEN IF YOU'RE CLIMBING THE DIGITAL STATION'S TRANSMITTING TOWER!!!
For example, if a station is digital only, you should be able to be on their tower with a radio, and be able to pick up a distant co-channel station just as clearly as if the digital station was off the air.

Also, the digital coverage should be much more efficient than the equivalent analog signal.
Take an analog CW signal, a high end $5+digit radio, and a properly tuned full wavelength or longer longwire antenna. When the analog signal is S1-12dB (yes, that's MINUS), or the CW signal using that equipment is basically pretty much almost unreadable, but you can still tell that there's something on the air, you just don't know WHAT it is, you should still be able to get at LEAST a 20kHz audio response, 5.1 channels, at least as compression artifact free as LAME encoded 320kbps MP3, and a 144dB signal to noise ratio, on a $1-digit to low 2-digit-teens walkman.
Also, you should be able to short space digital stations - for example even having stations just a few kHz apart diplexing from the same tower/array.

So, what would be the closest we could come to that?

What I could probably be satisfied with is:
CD quality sound that takes up the same bandwidth as a current 10kHz response C-Quam channel, with brick wall filters on the sides so that even radios with virtually NO selectivity will NOT, unless you're right under the tower, pick up a signal more than about 30 kHz off channel
when the analog is COMPLETELY gone on a good quality analog radio and antenna (for example SRF-42 and select-a-tenna), the digital is still completely clear on a cheap digital radio
digital does not interfere with analog - you can be at digital's tower and hear distant analog co-channel as clearly as if digital was off the air.

 

[rbrucecarter]

Everybody fails to mention self-jamming.

A radio has to be perfectly tuned to the frequency, or phase modulation of the 5 to 10 kHz sidebands makes no difference. They become amplitude modulated. Only digitally tuned radios have a chance to get interference free analog audio. Every IBOC AM station I have tuned with an analog tuned radio has substantial hash in the analog audio - except if I take the time to tune really carefully. That is assuming the radio I am using has sufficiently good mechanics to even let me tune carefully. The little "dial on the shaft of the tuning capacitor" type of radios are nearly impossible to tune for interference free audio. The further you get off center frequency, the worse the self-jamming becomes. As bad as it is on music formats, talk formats are worse. You can hear self-jamming between each word.

 

[CW]

> > details on his system or license receivers (which is why
> his
> > ISB Stereo system died....NOONE could build a rcvr to work
>
> > on his system well)...
>
> The construction of an ISB receiver is no huge secret.
> (heck, one could get noticable stereo separation by simply
> using two regular radios, carefully tuned...)
>
Yes, but there is some extra information in the Kahn signal as well that may be helpful in better reception or seperation...
Using two radios to pick up Kahn AMS is possible (listened to one station using that method!) but to get full effect, a REAL AMS rcvr designed for Kahn from the ground up was needed...and Leonard is such an idiot for not allowing others to see his technical details, none were really built...I have a Sony rcvr that could decode Kahn fairly well but I understand it was a compromise....

 

[PhilJSmith67]

Re: Everybody fails to mention self-jamming.

> A radio has to be perfectly tuned to the frequency, or phase
> modulation of the 5 to 10 kHz sidebands makes no difference.
> They become amplitude modulated. Only digitally tuned
> radios have a chance to get interference free analog audio.
> Every IBOC AM station I have tuned with an analog tuned
> radio has substantial hash in the analog audio - except if I
> take the time to tune really carefully. That is assuming
> the radio I am using has sufficiently good mechanics to even
> let me tune carefully. The little "dial on the shaft of the
> tuning capacitor" type of radios are nearly impossible to
> tune for interference free audio. The further you get off
> center frequency, the worse the self-jamming becomes. As
> bad as it is on music formats, talk formats are worse. You
> can hear self-jamming between each word.

This is very much the case with one of my local powerhouse stations. In fact, an engineer from the station wrote back to me confirming that "phase changes" caused by external structures, powerlines, conduit in walls, etc. could make the analog signal sound considerably worse than it did before the station implemented IBOC. I almost get the feeling that the engineer is not a big fan of iBiquity's implementation of IBOC, but peddles the company line because it's vital to job retention at that station.

This station sounds amazingly awful as I travel below underpasses, near small power lines or high-tension lines, or on portable radios in certain locations inside the house, where other stations fare much better. Not only the primary and secondary ensembles of the HD Radio signal become audible on wider-bandwidth receivers, but it seems as if the tertiary ensemble underneath the analog audio rises to the surface, even on narrow-IF radios. Driving down the road, it's as if someone turns on a blender every time I go under a bridge. Most other stations either remain stable, or simply lose volume in those situations.

All of this is in addition to the normal "open road" fidelity for the station, which is muffled like an old telephone, with a hint of a rushing noise in the background.

Of course, many people say that this is a technology that can deliver great fidelity plus data. That may be so. But, to compare it with Internet connections, the DSL and Cable providers didn't make Broadband successful by concocting a technology that artificially handicaps existing 56k dialups to operate at 20k. Perhaps this is why Eureka-147 is doing well in the rest of the world, because it is a completely *parallel* technology.<P ID="edit"><FONT class="small">Edited by PhilJSmith67 on 08/16/05 12:27 AM.</FONT></P>