ANOTHER BIG HD-AM PLUS: IT COULD BLOW UP YOUR TRANSMITTER!

[Savage]

Obnoxious, fatiguing artifact-laden codec. High costs. Self-interference and analog noise. Adjacent-channel interference. Encoding delay. Limited digital coverage. Necessitates drastically reduced analog bandwidth. Won't work with a large percentage of existing directional arrays. Engineers hate it; listeners couldn't care less.

To these well-known HD-AM features we can now add: IBOC-AM can damage power modules in the latest generation Harris 50kw transmitter, the 3DX-50.

There have now surfaced an increasing number of accounts - of course, in typical HD fashion, being forcibly hushed by IBOC powers-that-be - that the HD encoding and COFDM system can cause transient drive failure to MOSFETS in the PA modules of the popular high-power Harris AM transmitter being used by a large number of HD-equipped stations. Result: PAs shut down, forcing reduced-power operation until an engineer can make repairs.

There is at least one account of a 50kw midwest station that operates its older-generation transmitter - that's right, a BACKUP - because it's less susceptible to PA damage from HD encoding. Which of course means that the shiny new 3DX-50 is relegated to the status of being an expensive standby TX!

An unnamed source in the tech-support department at Broadcast Electronics stated that he was truly thankful for HD Radio. Without HD, the number of employees required to deal with technical problems and issues would likely be halved.

 

[rbrucecarter5]

I'd sure love to read the technical reports about exactly how the damage occurred. I am assuming that maintaining flat phase in a transmitter array over 50 kHz of spectrum would be difficult. But with the digital sidebands only operating at 500 W, I'm a little curious about how any realistic SWR mismatch at the extremes of the bandwidth could return any more than a few watts back into the MOSFETs.

If this can be documented, we should hear a lot more about it if they boost the sideband power on AM! This could really turn the tide against a return of investment on IBOC. I am wondering if it is the reason why analog coverage is also lost, engineers are quietly reducing the transmitter power just so they don't blow output stages ---

 

[JohnnyElectron]

I've noticed that WWJ Detroit has their HD off - both day and night the past month - and their analog audio is much better now too! Wonder if their HD smoked their new 50KW unit too?

 

[radiotower40]

Obnoxious, fatiguing artifact-laden codec. High costs. Self-interference and analog noise. Adjacent-channel interference. Encoding delay. Limited digital coverage. Necessitates drastically reduced analog bandwidth. Won't work with a large percentage of existing directional arrays. Engineers hate it; listeners couldn't care less.

To these well-known HD-AM features we can now add: IBOC-AM can damage power modules in the latest generation Harris 50kw transmitter, the 3DX-50.

There have now surfaced an increasing number of accounts - of course, in typical HD fashion, being forcibly hushed by IBOC powers-that-be - that the HD encoding and COFDM system can cause transient drive failure to MOSFETS in the PA modules of the popular high-power Harris AM transmitter being used by a large number of HD-equipped stations. Result: PAs shut down, forcing reduced-power operation until an engineer can make repairs.

There is at least one account of a 50kw midwest station that operates its older-generation transmitter - that's right, a BACKUP - because it's less susceptible to PA damage from HD encoding. Which of course means that the shiny new 3DX-50 is relegated to the status of being an expensive standby TX!

An unnamed source in the tech-support department at Broadcast Electronics stated that he was truly thankful for HD Radio. Without HD, the number of employees required to deal with technical problems and issues would likely be halved.

Savage, Is there anyway you can disclose which station that is using the backup TX, I think I know which one it is but, I'm not
positive. If you can't disclose who it is I understand. Thanks, TR

 

[LinoNYC]

Obnoxious, fatiguing artifact-laden codec. High costs. Self-interference and analog noise. Adjacent-channel interference. Encoding delay. Limited digital coverage. Necessitates drastically reduced analog bandwidth. Won't work with a large percentage of existing directional arrays. Engineers hate it; listeners couldn't care less.

To these well-known HD-AM features we can now add: IBOC-AM can damage power modules in the latest generation Harris 50kw transmitter, the 3DX-50.

There have now surfaced an increasing number of accounts - of course, in typical HD fashion, being forcibly hushed by IBOC powers-that-be - that the HD encoding and COFDM system can cause transient drive failure to MOSFETS in the PA modules of the popular high-power Harris AM transmitter being used by a large number of HD-equipped stations. Result: PAs shut down, forcing reduced-power operation until an engineer can make repairs.

There is at least one account of a 50kw midwest station that operates its older-generation transmitter - that's right, a BACKUP - because it's less susceptible to PA damage from HD encoding. Which of course means that the shiny new 3DX-50 is relegated to the status of being an expensive standby TX!

An unnamed source in the tech-support department at Broadcast Electronics stated that he was truly thankful for HD Radio. Without HD, the number of employees required to deal with technical problems and issues would likely be halved.

"There have now surfaced an increasing number of accounts - of course, in typical HD fashion, being forcibly hushed by IBOC powers-that-be"

How convienient.

"An unnamed source"

Leave it to ol' Bob Savage to find the "Deep Throat" in the HD radio scandal.

I know the spec's and the power levels even at the duty cycle involved would be unlikely to cause failure in even a grossly mis-designed install.

Without stations calls and/or personell on-record it's just ol' Bob creating mischief as usual.

Lino

 

[Kelly]

This post is just silly. The claims are undocumented, and whenever conspiricy claims are made too, I discount the claim.

If the station were operating with a mis-adjusted, or faulty antenna system causing excessive sideband VSWR, my bet is they would have a higher failure rate of MOSFETS whether transmitting digital sidebands or not.

 

[Tom Wells]

The post is not silly. HD sidebands, as far as an AM transmitter is concerned, are very much like a strong parasitic oscillation running 100%,
along with the analog at some variable level. Any "uncontrolled" parasitic oscillation is likely to take out output devices.
The HD sidebands may be "controlled", but the poor gates of the MOSfets don't know it's intentional.

I'll bet the ibiquity people have never had to tame an unstable transmitter with parasitics, or they'd know how easy it is to smoke
outputs. Well, it sounds like they're learning about radio as they go. Why didn't they avail themselves of experienced radio engineers?

Digital efficiency at its best.

 

[LinoNYC]

The post is not silly. HD sidebands, as far as an AM transmitter is concerned, are very much like a strong parasitic oscillation running 100%,
along with the analog at some variable level. Any "uncontrolled" parasitic oscillation is likely to take out output devices.
The HD sidebands may be "controlled", but the poor gates of the MOSfets don't know it's intentional.

I'll bet the ibiquity people have never had to tame an unstable transmitter with parasitics, or they'd know how easy it is to smoke
outputs. Well, it sounds like they're learning about radio as they go. Why didn't they avail themselves of experienced radio engineers?

Digital efficiency at its best.

Tom, forgive me but you are out of your element here and need to do some reading about the iboc system and the sort of transmitters that are designed for it.

I'am not in the business either but have read and researched enough to know that we are not talking about a neutralization here. The injection level is slightly more than 1/100th of the quiescent carrier power, even an ancient 1950s tx w/rated average mod of only 30-40% could handle this..if it had the bandwidth and phase characteristics.

Add to that the fact modern tx' all have continual status monitoring and automatic protection...you'll realize that the original post was full of ..it.

Lino

 

[KB1OKL]

Lots of new cool selling points for iBlock every day, don't you love it? I wonder if I can blow up my 6293 final tubes in my DX-100 with iBlock?

 

[Savage]

First of all, it's not a single station which has reported MOSFET failures from IBOC operation. There are several. If you survey CEs at major 50kw stations you will find just about everyone is familiar with the 3DX-50 failures. I would suspect a number of them have experienced the problem themselves.

Tom Wells is right. The encoding algorithm under some conditions apparently causes a very brief - probably, in nanoseconds - loss of biasing which fries the MOSFET junction. Harris is very clear in its tech data that drive must never be lost to prevent damage to PA transistors. A circuit in the PA provides the MOSFET drive and the HD encoding can interfere with this drive if conditions are just right.

The failures are NOT related to antenna or load conditions.

I can't give the callsign of the station which has relegated its 3DX-50 to standby because I promised not to go public with it to the source, who is a well-known consulting engineer and regular RW advertiser (and I guess you would describe him as a member of the vast "naysayer" conspiracy.) But the station involved might be in a couple of cities kinda near a big river somewhere.

 

[4dude]

I hope this whole IBOC garbage blows up right in thier faces!!!!

HD is garbage and just and excuse to mock up our analog airwaves!!

 

[LinoNYC]

First of all, it's not a single station which has reported MOSFET failures from IBOC operation. There are several. If you survey CEs at major 50kw stations you will find just about everyone is familiar with the 3DX-50 failures. I would suspect a number of them have experienced the problem themselves.

Well, ok, discounting that last sentence which is supposition the fact is that these tx' have been on the market for 10-11 years ?, they are the dominant brand for full power AM iboc and with 240 AM hd stations on-air if this were a notable problem, wouldn't we have read something...credable?

from Harris' blurb:


The 50 kW DX Destiny uses 62 main
and six binary solid-state RF power
amplifiers. These modules protect
themselves from over-temperature,
loss of RF drive, loss of power and
shorted RF output conditions, and are
hot-pluggable for on-air servicing.
These modules are of simple
construction with easy access to the
individual MOSFET transistors.

Tom Wells is right. The encoding algorithm under some conditions apparently causes a very brief - probably, in nanoseconds - loss of biasing which fries the MOSFET junction.

As I read it, Tom compares this to a case of parasitic oscillation, saturating and causing punch-through of the junctions. BTW: I have wide and long experience with mosfet devices and his contention is valid, but not in this case.

and I guess you would describe him as a member of the vast "naysayer" conspiracy

Conspiracies are your dept. Come on Bob, radio engineering is very fraternal, if this were an issue, no one, not even the "iboc powers that be" could "forcibly hush this bunch.

Lino

PS: I sent the WADO file to a Mexican friend who manages one of my locations and listens to the station on his drive home each night. He just wrote back that "it sounding super...really good" and wants to buy a radio for his car. You and I may not think AM iboc sounds that great (I don't) but to average, non-critical people it's a revelation for AM to sound like that and offers the band hope for a future.

 

[Savage]

No problem. I understand people want sources for info cited. Let me see if I can get someone to go on the record about this. But I can state: it's not an isolated or single-station phenomenon.

Wait: breaking news. This from a well-known consultant in Birmingham, Alabama who e-mailed me:

"...my thoughts about what is going on at Crawford's 850 kHz WXJC. It appears they are running on their backup Tx....power is down but it is in full (glorious) analog mode.

"...about a month ago, their IBOC exciter went nuts, no analog and pure digital pulsing over 300 kHz. Could it be that yet another Tx has been fried?"

He then goes on to theorize that Crawford may be negotiating with iBiquity over a settlement to repair the station's damaged 50kw Tx. (Memo to Don Crawford: Remember the parable of "throwing the first stone?" Your broadcasting organization purports to embrace Christian principles of tolerance and humility. Maybe this would be a good juncture to advise your engineering people that publishing arrogant, mean-spirited letters about HD Radio in industry trades, insulting IBOC critics and calling them names like "naysayers" (as opposed to defending HD Radio) might not be the best reflection on your company. Just a thought.)

 

[Kelly]

You know this whole issue could be settled by just having a requirement that stations turn off their analog AM modulation by say..January 2012. Digital modulation is superior anyway, so why keep trying to save analog?? Oh that's right, for DX'ers! What was I thinking??

Remember, everytime you see a funeral procession, AM loses another AM listener!

 

[Savage]

Very glib, Kelly. Haw haw haw the funeral thing. The all-digital proposal would be so groooovy...except....nobody cares. Nobody's going to trash his analog radio. If listeners want to listen to digital audio entertainment they'll get it from the internet.

Please, with the "DXers" argument. IBOC boosters maintain that everyone outside the 70 dBu (FM) or NIF (AM) is by definition a "DXer" and thereby subject to derision and outright hostility. This is denial of real-world listening conditions rejected by 99.99% of the industry.

HD isn't a cure for radio's ills. It's corporate-injected laetrile which is endangering the life of the patient.

You want to talk 2012? In 2012, the HD exciter will be gathering dust in that transmitter site backroom where discarded equipment gathers dust - your iBiquity Decepticon will be sitting on a shelf next to the dented Modulimiter with the missing output meter, the busted QRK turntable with no pickup arm, and your Ampex Cue-Mat.

 

[Savage]

Generally speaking, Lino, I ignore your posts which include insults and other inappropriate comments. But I don't mind responding to your observation about the "fraternal" nature of radio broadcast engineers.

How right you are. And approximately 160 registrants, almost entirely engineers - station and consulting type - have joined the Stop IBOC Alliance at www.stopiboc.com. When I get a spare moment I'm going to construct a new page including location by state and post some quotes. The "fraternity" of engineers have spoken on HD. And they hate it.

The stopIBOC data is a devastating condemnation of HD Radio from professionals in the field. Some are observations in the "Confessional" and some are just e-mails describing unfortunate experiences with HD Radio. Read with the ongoing negative press about HD in trades and audiophile pubs and blogs, the evidence is overwhelming: HD-FM is fast becoming the disaster HD-AM has already proven to be.

If the dwindling herd of IBOC enthusiasts thinks that loyal radio engineers are the last line of defense for HD Radio, they're going to be disappointed in most cases - unless those engineers happen to work for Crawford.

 

[LinoNYC]

Generally speaking, Lino, I ignore your posts which include insults and other inappropriate comments. But I don't mind responding to your observation about the "fraternal" nature of radio broadcast engineers.

How right you are. And approximately 160 registrants, almost entirely engineers - station and consulting type - have joined the Stop IBOC Alliance at www.stopiboc.com. The "fraternity" of engineers have spoken on HD. And they hate it.

Regarding "insults and inappropriate" comments, I believe you have, as usual, ignored your own mocking, derisive and sometimes bigoted remarks. Look in the mirror.

Now we have the "And approximately 160 registrants, almost entirely engineers - station and consulting type" the FCC lists 13486 radio stations in the USA. Even if all your signers were engineers and all contracted for an appalling 10 stations each...well.. not exactly a plurality, especially given that you've been pounding this drum for over a year.

_And as usual: no documentation. Given your record I would not believe anything on your website, Sorry.

A case-in-point from one of your other responses:

"Essentially, you need a 50kw NDA signal to get even "acceptable" HD operation. "

In my daily experience this is not true. WNYC-am 10K WADO 50Kd-7Kn, WQEW (when iboc is on) are all directional as is WOR and all decode reliably given just the loop supplied with the Acurian.

"And that assumes your listening environment is free of noise or other types of LOCAL interference. As has been repeatedly noted here, that isn't a practical assumption either."

This is a legitimate point although it pertains only to AM and in my experience, it's not difficult to achieve decent AM as long as you keep the antenna a few feet away from local noise sources. If you receive clean AM from a local station, you should get iboc to decode.

"With consumer products you don't get a second bite of the apple. If the product isn't ready, and doesn't capture the imagination and desire of the target market consumer, it's dead. You don't get another chance. "

This is the sort of statement that you often make and given your background and experience it's really duplicitous.

We had over twenty years of green and magenta faces on ntsc color tv, FM has gone from problematic to great (Alford era) and now poor again with all the obstructions causing multipath (something FM iboc deals with well btw). There are so many products released within our lifetimes that performed poorly at first, you simply aren't credible when making a statement like that.

Another unsubstantiated claim:

"The likely first adopters for HD Radio have bought their first units, and a huge proportion - according to some sources, most of them - have been returned as "defective." "

Not according to the dealer I spoke to at one of my local Radio Shack stores, only the BA was a problem (for reasons we a well aware of) and the Acurian did receive some reception complaints that were answered with a rabbit ears. Unfortunately this probably means no one cared about the AM. These same salesmen's remarks about ota astc reception were totally different ie: forget it.

That's why the BA Receptor HD is history. So on the purchaser and manufacturer ends HD had its shot, and blew i

Again use your historical perspective and be honest.

Lino

 

[Kelly]

Very glib, Kelly. Haw haw haw the funeral thing. The all-digital proposal would be so groooovy...except....nobody cares. Nobody's going to trash his analog radio. If listeners want to listen to digital audio entertainment they'll get it from the internet.

Please, with the "DXers" argument. IBOC boosters maintain that everyone outside the 70 dBu (FM) or NIF (AM) is by definition a "DXer" and thereby subject to derision and outright hostility. This is denial of real-world listening conditions rejected by 99.99% of the industry.

HD isn't a cure for radio's ills. It's corporate-injected laetrile which is endangering the life of the patient.

You want to talk 2012? In 2012, the HD exciter will be gathering dust in that transmitter site backroom where discarded equipment gathers dust - your iBiquity Decepticon will be sitting on a shelf next to the dented Modulimiter with the missing output meter, the busted QRK turntable with no pickup arm, and your Ampex Cue-Mat.

You know Savage, you are SO wound up about the IBOC-HD radio issue, that you don't even read the posts before you start typing. So, read my post..

I'm not a proponent for IBOC. I'm for doing away with amplititude modulation on the MW band completely. A few years ago I suggested to the NAB, that stations be allowed to apply for an experimental license in the "expanded band" that would allow stations to broadcast at 1kW, ND, full digital modulation. As with TV, then stations would be required to convert to full digital modulation and receiver producers would need to have digtal capable demods in all car radios and all tuners by 2010. By January 2012 traditional amplititude modulation would be eliminated on the Medium Wave band.

Not only would that end this stupid bickering among broadcast engineers over 40 years old, but it would potentially create a re-birth for a "new" form of radio for the youth that doesn't know AM exists, nor would they care if they did.

 

[RadioMan203]

It seems like the only folks making out on this is iBiquity. I wish I could develop a codec and then rape my client audience with those kind of licensing fees!

In comparison, I don't hear (no pun intended) computer software folks like Real, M$ or Apple raping people of the use of their streaming codec technologies. I guess the folks at iBiquity need to guarantee their kids' college education somehow!

So now you have to worry about the HD stressing your transmitter? At least it gives more folks good reason to toss that HD stuff in the dumpster! I hear more and more buzz about AMs pulling the plug on HD from interference issues. It sounds like HD has no business on AM at all now.

Could you imagine if iBiquity started to sell the same bill of goods to shortwave broadcasters? As an engineer I'd just love to have my big ol' shortwave "soil the linen" thanks to HD-sw.

Let's all pull our C-Quam exciters out of mothballs and put those back on the air!

 

[Savage]

Well, Kelly, this IS the HD Radio board, and the sentiment often expressed here by IBOC proponents is that the interference issues could be eliminated by quickly morphing AM (and FM) service in-band to all-digital, and dumping analog. While you're right that your post didn't specifically reference that, it's easy to infer.

Your post didn't propose all-digital operation in the expanded band. You simply said AM should be all-digital by 2012. And my responses here and earlier are equally true: it's not going to happen via either avenue, HD or not, with an analog receiver population variously estimated between 500,000,000 and 800,000,000.

If terrestrial radio's going to go digital, the only sane way to do it is through interim dual operation on existing and new allocations, with a transition to the new frequencies a la broadcast TV. Since there isn't the industry interest or political will to get this done, it won't happen. So terrestrial radio is going to remain largely analog with digital simulcasts available via alternate delivery methods: the internet, and possibly through an alliance with what's left of XM and Sirius once they burn through all the remaining capital in the free world.