Without HD - Improving FM (Stereo)

[iyiyi]

Yeah... But...

Every method used to "improve analog FM" results in a trade off for audio quality. Blending to mono, narrowing bandwidth, pre distorting the audio (equalizing), fooling with de-emphasis adjustments, trying to hang digital subcarriers on (and in lieu of) the SCA portion the signal... Every 'improvement' - including analog DSP - compromises the audio in some manner.

I used to think that, and even had some negative things to say about the analog performance of the venerable Sony XDRF1-HD (somewhat revered by FM enthusiasts these days). But we bought one of those BW Broadcast receivers to use at a translator site that is receiving severe HD interference from an adjacent-channel station. All I can say is you should take a listen for yourself. You'll be a believer. Doing an A/B comparison between over-the-air HD and over-the-air analog with the RBRX1 we chose the analog receiver for the translator input. In either case the preamps and/or source material in the studio were the limiting factor in the S/N ratio, and the analog signal didn't have the digital artifacts.

There may be some compromise of the analog audio, but it's not as bad as HD encoding/decoding.

Dave B.

We are talking about completely different things.

You are discussing a legitimate, application specific and customized solution to a very complex, real-world broadcast engineering problem.

There should be no reason for a properly programmed, installed and set up HD to HD link to have objectionable artifacts. Is the HD equipment from the importer to transmitter of factory design or is it an ad hoc assemblage? Something is incorrectly set. I suggest that you seek professional HD guidance because your HD should easily make this link. 1st adjacent HD digital/ HD digital sideband interference is not an issue. The upper/ lower adjacent sidebands have a net 90 degree differential and have reasonable rejection in the QAM detector. A knowledgeable person should comb and correct your HD. Otherwise you are not getting the performance from your system that you have paid such a goodly sum for!

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[diymedia]

Is the HD equipment from the importer to transmitter of factory design or is it an ad hoc assemblage? Something is incorrectly set. I suggest that you seek professional HD guidance because your HD should easily make this link.

Yep, so easy that they're still sussing it out in the pages of RW Engineering Extra:

http://www.nxtbook.com/nxtbooks/newbay/rwee_20130417/#/4

 

[iyiyi]

Is the HD equipment from the importer to transmitter of factory design or is it an ad hoc assemblage? Something is incorrectly set. I suggest that you seek professional HD guidance because your HD should easily make this link.

Yep, so easy that they're still sussing it out in the pages of RW Engineering Extra:

http://www.nxtbook.com/nxtbooks/newbay/rwee_20130417/#/4

Good article! Thanks for turning me on to this great info!

Main points to be gleaned here are: There's far too many opportunities for big audio processing setup gaffes. There's far too few people with proper understanding and knowledge of HD technology. HD radio is strictly radiotelegraphy. Many radio people just flat out do not, cannot or will not understand that radiotelephone and radiotelegraph are two completely different animals. This mentality will persist on the FM band for quite some time. Soon the MW band will get a whiff of that success HD radio is capable of delivering to it; AND the HD-capable MW set penetration will reach HD's event horizon. AM broadcasters will jump to HD like lemmings.

HD radio just will not lend itself easily to a hack or a 0.5 assed set-up or installation. It can turn around and bite you quickly for that error!

iBiquity could help things by issuing simple, easy to comprehend guidelines of various transmitter and processing schemes that work, don't work or can serve as a contingency. HD radio's three big problems, IMHO, is: Under powered (needs at least -10 dBc and -6 dBc would be almost ideal); HD set market penetration is currently way below HD's event horizon; insufficient equipment, knowledge and guidance is available for many techs to properly set up and process a HD audio chain.

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[xmtrland]

So the problem with HD radio is that the majority of Broadcast Engineers are too uneducated to implement it correctly. And until that bread of engineer is gone this problem will persist. Also the Public is too uneducated to by HD radios??

iBiquity made a system that is so superior and cutting edge that Broadcast engineers just don't get it. That shows some screwed up marketing and education on how to use the product....by iBiquity

Sounds like we were wrong to compare the audio quality of HD radio to analog radio (radiotelephone). What we need to do is compare the HD quality to a radiotelegraph, yup that makes perfect sense. But even then I don't hear Digital artifacts in the regular Radiotelegraph, but do in the Ibiquity version. Obviously that can be blamed on the stupid stupid engineers that no longer understands the medium of radio.

Just one question. Why does the Ibiquity system require so much bandwidth if it is so much like Radiotelegraph? How much bandwidth is used for radiotelegraph?

I'm an uneducated broadcast engineer with poor understanding and knowledge of HD radio technology. To better myself I'm dusting off my old radio telegraph key. Maybe for the cost of broadcasting HD iBiquity could throw in a telegraph key and code book, obviously what they are doing now is not connecting with the engineer to install the system correctly.

 

[diymedia]

I haven't keep track of the number of times I've heard this particular exchange:

Broadcast engineer to iBiquity: "We have a problem with the system."

iBiquity to broadcast engineer: "You need to talk to the transmitter manufacturer."

Broadcast engineer to transmitter manufacturer: "We have a problem with the system."

Transmitter manufacturer to broadcast engineer: "You need to talk to iBiquity."

...repeat ad infinitum.

 

[iyiyi]

I haven't keep track of the number of times I've heard this particular exchange:

Broadcast engineer to iBiquity: "We have a problem with the system."

iBiquity to broadcast engineer: "You need to talk to the transmitter manufacturer."

Broadcast engineer to transmitter manufacturer: "We have a problem with the system."

Transmitter manufacturer to broadcast engineer: "You need to talk to iBiquity."

...repeat ad infinitum.

Broadcast engineer to broadcast engineer: "You get paid to 'fix' the problem. Not whine over the telephone that it is 'broken'.".

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[audioguy]

You can't fix something that isn't designed properly in the first place. It's time to give up on HD Radio and look for a better solution!

 

[xmtrland]

I stand corrected and better educated. iyiyi is correct, HD Radio is very much more like radiotelegraphy or just telegraphy versus Radiotelephone. Radiotelegraphy is just Telegraphy carried via radio. Telegraphy requires that the method used for encoding the message be known to both sender and receiver (kind of like HD radio, encoder/decoder). If you drill down to the basic examples of telegraphy you get Refelcted light, Flag semaphore and Smoke Signals. With Radiotelegraphy it would be Morse code and the ibiquity HD radio system which is a much improved Smoke signal.

Obviously understanding this early Smoke signal technology will help every broadcast engineer better understand HD Radio. And understanding the reflected light technology especially using mirrors is vital in making a system work built around Smoke and Mirrors technology.

 

[DaveBayArea]

We are talking about completely different things.

Not really. I'm talking about a serious effort to improve FM reception quality - the topic of this thread. A run-of-the-mill translator system was WAAAAY too noisy because of adjacent-channel HD radio interference on the input (not self-interference, I'm speaking of the HD carriers from 89.3 landing on 89.5). Legally we're required to receive the primary station off-air. So we went looking for another method. The two choices were:

1. Receive and rebroadcast the HD transmission.
2. Try to eliminate the noise on the received analog signal

Option number two provided better quality audio, and that's what we chose to do.

There should be no reason for a properly programmed, installed and set up HD to HD link to have objectionable artifacts. Is the HD equipment from the importer to transmitter of factory design or is it an ad hoc assemblage? Something is incorrectly set. I suggest that you seek professional HD guidance because your HD should easily make this link. 1st adjacent HD digital/ HD digital sideband interference is not an issue. The upper/ lower adjacent sidebands have a net 90 degree differential and have reasonable rejection in the QAM detector. A knowledgeable person should comb and correct your HD. Otherwise you are not getting the performance from your system that you have paid such a goodly sum for!

When the interfering signal is that of another station the upper-lower sideband problem is a big one indeed. That's our issue, and in fact that is the entire reason we secured this translator. It brought back thousands of listeners that were lost with the implementation of HD Radio. While I wasn't part of the original implementation, it was done as a turnkey by Harris with an Omnia and it's all reasonable.

Your definition of "objectionable artifacts" is certainly up to the individual listener. I know I can hear the clanky-swooshy sound of an AAC codec that I first became familiar with on XM - especially when airing cell phone calls. Whether 1%, 5%, or zero listeners would notice if we used the HD signal for the translator rebroadcast, I'm not sure. But why should we retransmit a compromised signal when a better one exists by simply taking the analog broadcast from the primary station?

Dave B.

 

[kfbkfb]

Perhaps something like the Carver TX-11b FM tuner,
but implemented with digital methods.

A more complex option would be to use something
like the NoNoise process on the L-R subcarrier to try to
reduce the noise before the L and R matrix process.

Kirk Bayne

 

[KB1OKL]

I suggest that you seek professional HD guidance because your HD should easily make this link.

You mean like an HD radio psychologist?

AM Radio station owner: "You mean we spent every last penny on a system that nobody likes or listens to... and no one can even receive outside of a 5 mile radius around the towers???"

Psychologist: "Now now, don't cry, it's not that bad, when this whole thing blows over at least you got C Quam on the equipment."

Owner: " But you don't understand!! This was our great last hope, we were told it was going to be the next big thing in radio, it was going to save the AM band from becoming the 300M ham band!"

Psychologist: "Well look at it this way, if all else fails you can always sell the junk for scrap"

Owner: "Boo hoo! woe is me! I should have never trusted that long faced weasel"

 

[DaveBayArea]

Perhaps something like the Carver TX-11b FM tuner,
but implemented with digital methods.

A more complex option would be to use something
like the NoNoise process on the L-R subcarrier to try to
reduce the noise before the L and R matrix process.

Kirk Bayne

There's also the SSB-SC method described here:

http://omniaaudio.com/mpx-ssb-white-paper

Several stations are testing it right now under STA.

Dave B.

 

[iyiyi]

We are talking about completely different things.

Not really. I'm talking about a serious effort to improve FM reception quality - the topic of this thread. A run-of-the-mill translator system was WAAAAY too noisy because of adjacent-channel HD radio interference on the input (not self-interference, I'm speaking of the HD carriers from 89.3 landing on 89.5). Legally we're required to receive the primary station off-air. So we went looking for another method. The two choices were:

1. Receive and rebroadcast the HD transmission.
2. Try to eliminate the noise on the received analog signal

Option number two provided better quality audio, and that's what we chose to do.

There should be no reason for a properly programmed, installed and set up HD to HD link to have objectionable artifacts. Is the HD equipment from the importer to transmitter of factory design or is it an ad hoc assemblage? Something is incorrectly set. I suggest that you seek professional HD guidance because your HD should easily make this link. 1st adjacent HD digital/ HD digital sideband interference is not an issue. The upper/ lower adjacent sidebands have a net 90 degree differential and have reasonable rejection in the QAM detector. A knowledgeable person should comb and correct your HD. Otherwise you are not getting the performance from your system that you have paid such a goodly sum for!

When the interfering signal is that of another station the upper-lower sideband problem is a big one indeed. That's our issue, and in fact that is the entire reason we secured this translator. It brought back thousands of listeners that were lost with the implementation of HD Radio. While I wasn't part of the original implementation, it was done as a turnkey by Harris with an Omnia and it's all reasonable.

Your definition of "objectionable artifacts" is certainly up to the individual listener. I know I can hear the clanky-swooshy sound of an AAC codec that I first became familiar with on XM - especially when airing cell phone calls. Whether 1%, 5%, or zero listeners would notice if we used the HD signal for the translator rebroadcast, I'm not sure. But why should we retransmit a compromised signal when a better one exists by simply taking the analog broadcast from the primary station?

Dave B.

Let me try it from this angle: We now know that Harris installed a turnkey HD operation for your station. We can safely assume that your HD equipment is properly chosen, compatible and correctly installed. I agree with you that it is all reasonable. The Omnia of and by itself is not an issue whatsoever in the HD sound quality. The Omnia's SETTINGS OTOH... I am certain that a phone call to Omnia would provide a default setting to start and the counsel needed to advise you on it's correct setup for your operation. It sounds to me that your HD "artifact" problems could be as simple as a level that is slightly too high. You were presented two options. One involved using a HD signal that needs little more than a tweak for a quality feed to the translator. The other option was to settle for an expensive, jury-rigged analog feed. It appears that you decided to settle. I would have performed all tweaks possible and gone with the superior digital HD feed. My question to you is: Why should you hack and retransmit a compromised analog signal when a better one exists by simply taking the superior HD digital broadcast from the primary station?

You and I approach the situation differently. 1st thing I would do is get the HD tweaked for clean audio. Good equipment and install here so there is no reason for less than 100% HD quality audio. 2nd I would discuss the signal issues at the next station meeting and request a morning to kill 88.5 for a couple or three hours. With 88.5 off-air I would drive the 88.3 signal and - using garden variety radios - determine just exactly what extent both 88.3's "directional" analog AND digital signals encroach 88.5's 60 dBu contour. I would drive the 88.3 contour areas where 88.5 allegedly interferes to see how 88.3 does on its own. I would then activate the 88.5 signal in analog mode only and replicate the first drive and observe 88.3's hybrid signal's effect on 88.5's analog only signal and vice versa. Finally I would kill the 88.5 analog, fire up 88.5's HD and again redrive the route. This time you determine the 88.3 hybrid/88.5 pure digital interplay over their respective coverage areas. You now know exactly what you have and where you stand on this issue.

The 88.3 upper HD sideband interferes with the 88.5 analog signal in 88.5's weaker signal areas. 88.5's lower HD sideband interferes with 88.3's analog signal in 88.3's weaker signal areas. 88.3's upper HD and 88.5's lower HD digital sidebands do not affect each other in that manner. Find a spot where 88.3 and 88.5 both provide strong signals. Both stations should lock on HD and provide perfect HD digital sound.

I understand that 88.3 and 88.5 both run HD at -14 dBc. I believe that 88.3 and 88.5 can lower their adjacent HD sidebands to -20 dBc. How did that work out?

Mechanical beam tilt for both 88.3 and 88.5 as compensation for the unique terrain between the 2 stations is another possible option.

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[DaveBayArea]

You and I approach the situation differently.

In many ways, yes. In some ways, no. We've done the tests and have determined that two sets of RF carriers cannot occupy the same spectrum at the same time. That would be the RF version of Newton's 1st law of motion. It's useless for me to lobby for anything like a Neural audio processor for the HD when there might be only one or two HD radios active in the market at any time, and of those, they will constantly be falling back to Analog because of adjacent-channel interference to the HD carriers. I don't think I've mentioned it here, but there's also an 89.7 licensed to Lodi that bothers the other set of HD carriers. The result is no reliable HD reception six miles from our class B-1 transmitter.

I looked upon the HD receiver as a kluge - not the analog one built for Translator service. To the best of my knowledge there is no off-the-shelf HD receiver suitably set up to drive a translator (with RF muting when the receive signal is lost). So not only does the analog receiver have better audio quality, it integrates into the translator setup nicely.

Dave B.

 

[iyiyi]

You and I approach the situation differently.

I looked upon the HD receiver as a kluge - not the analog one built for Translator service. To the best of my knowledge there is no off-the-shelf HD receiver suitably set up to drive a translator (with RF muting when the receive signal is lost). So not only does the analog receiver have better audio quality, it integrates into the translator setup nicely.

Dave B.

Sorry for the 88s instead of 89s in the last post.

$2k for a top shelf analog receiver designed to plug and play rebroadcasts over a translator! Certainly a good investment and should provide years of excellent service.

I would exchange that unit for one with RBRX1 style analog features and the foresight to have also included HD reception capabilities. This also provides an excellent analog backup signal if the HD goes down. You currently have all the analog "whistles", but none of HD's "bells".

Receivers without HD capabilities are no longer "tomorrow's technology".

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[KB1OKL]

Receivers without HD capabilities are no longer "tomorrow's technology".

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You're right they're yesterday's.

 

[iyiyi]

Receivers without HD capabilities are no longer "tomorrow's technology".

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You're right they're yesterday's.

Exactly!

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[iyiyi]

$2k for a top shelf analog receiver designed to plug and play rebroadcasts over a translator! Certainly a good investment and should provide years of excellent service.

I would exchange that unit for one with RBRX1 style analog features and the foresight to have also included HD reception capabilities. This also provides an excellent analog backup signal if the HD goes down. You currently have all the analog "whistles", but none of HD's "bells".

Receivers without HD capabilities are no longer "tomorrow's technology".

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Sorry for not following through! An excellent example of what I'm trying to say is the DaySequerra M4.2S. Rack mountable, XLR outputs. Internet accessable controls. $990. More options, less coin, more versatile. Gives opportunity to easily A/B analog/HD signal translator feeds under real operating conditions.

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[KB1OKL]

Sorry for not following through! An excellent example of what I'm trying to say is the DaySequerra M4.2S. Rack mountable, XLR outputs. Internet accessable controls. $990. More options, less coin, more versatile. Gives opportunity to easily A/B analog/HD signal translator feeds under real operating conditions.

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Looks like Dab in Europe will be yesterday's technology, see post on "Radio in Smartphones will kill DAB". Can IBOC be far behind?

 

[DaveBayArea]

Sorry for not following through! An excellent example of what I'm trying to say is the DaySequerra M4.2S. Rack mountable, XLR outputs. Internet accessable controls. $990. More options, less coin, more versatile. Gives opportunity to easily A/B analog/HD signal translator feeds under real operating conditions.

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Not sure if you're on the pubtech mailing list or not, but there's a lot of discussion about that unit right now. Some of it not so good. But I am curious as to how it does in the midst of HD interference and how it adapts to fading signals - two areas where the BWBroadcast unit really excels. We may try one for one of our new sites if any of our pending translator apps are actually granted.

Dave B.