• Get involved.
    We want your input!
    Apply for Membership and join the conversations about everything related to broadcasting.

    After we receive your registration, a moderator will review it. After your registration is approved, you will be permitted to post.
    If you use a disposable or false email address, your registration will be rejected.

    After your membership is approved, please take a minute to tell us a little bit about yourself.
    https://www.radiodiscussions.com/forums/introduce-yourself.1088/

    Thanks in advance and have fun!
    RadioDiscussions Administrators

Clandestine testing or just another IBOC screw up?

K

KB1OKL

This is a long one and I apologize but the following is from an acquaintance who experienced a strange phenomenon the other day. I thought this may be very interesting to the engineers here. He encountered an HD station with the analog carrier completely off but the digital component was still working with audio and was able to be listened to on his radio, the hitch was that with the analog carrier off his HD radio couldn't detect the digital IBOC carrier in scan, his signal strength meter read zero and he had to manually tune it to the correct frequency, the radio went right by the digital only station when it was on scan. My question besides the obvious incompatibility issues with existing IBOC receivers was this just another in the myriads of times IBOC transmission has screwed up or was this a clandestine experiment and if so was it legal?

Part one of his post:

1. A local FM station stopped transmitting their hd signal for several
weeks and then, all of a sudden, the digital signal appeared and the
analog was gone! As far as I can tell the usual un-modulated FM
carrier was completely missing and signal strength went to zero but
the modulated hd signal was there.

The interesting thing about all this was that the SonyXDR-S3HD
completely ignored the hd signal in hd scan mode. You had to manually
tune the radio to the correct frequency so that the radio could
detect the hd component and produce an audible signal.


All this tells me that probably every HD radio in existence today, will
not work correctly if/when hd becomes the norm. The listener will
tune right past the signal without even knowing it.


Bottom line – There are so many unresolved issues concerning hd radio.
So many glitches and bugs not to mention the fact that no one is
listening and no one wants it.

Part two in response to my question: "Did you get audio or just a carrier? "

2. The modulated FM carrier and was completely gone, signal strength was zero, the analog signal was not present - as if the transmitter went off the air. It lasted for about 2 hours till they must have noticed and then the carrier went back, the analog signal re-appeared along with the signal strength meter.

With the analog signal gone the "HD" detection identifier on the radio was solid "on" with zero signal strength. The receiver was detecting only the digital component - playing away. I was using the Sony XDR-S3HD.

IBiquity's dirty little secret that they don't want consumers to know is that HD radios today will not work correctly in the future. Consumers will be "upgrading" which could kill radio altogether.
 
Guys, you know nobody is a more virulent opponent of HD than I am. It's hard to express which is more outrageous: the technical jerry-rigging and fudging, or the incessant lying about the system, its characteristics and negatives.

At the same time I have to state it's really a stretch to interpret this incident as some kind of sinister digital-only experiment. No station operator in his/her right mind would deliberately shut off the analog carrier. That's the only component of the signal that has any listeners. Suppose one or two analog listeners had Arbitron diaries in hand when the analog went off? Your little digital stunt just cost you trackable audience. If you wanted to perform a digital-only experiment you'd do it in the middle of the night when listeners are few or some other low-audience period, like 6am Sunday.

No, I'm certain this was just another in the endless parade of HD technical meltdowns that went undetected by an overworked, overextended engineering staff. Perhaps the station is dependent on a contract engineer who wasn't instantly available, or who may have been tending co-owned stations in the home or another market.

In 1955, this kind of technical problem would have been detected instantly by the duty First Phone Operator, a member of the staff which tended the transmitter site 24-7. It's 2009. There are many examples of five, six or nine signals and as many sites being maintained by one or two guys. So it's not surprising it took two hours to correct.

I respectfully suggest: we shouldn't invite criticism to the effect that IBOC opponents are paranoid bomb-throwers. That being said, the Sony radio's performance when confronted with a pure digital carrier does indeed seem instructive. And not in a good way, from the perspective of HD boosters.
 
Savage,

Thanks for the dose of sensibility (albeit backhanded) to this thread. And thanks to KB for not lacing his original post with the "iniquity, Stumble" slurs. Both are refreshing, unlike the Radio Racket's elementary school jokefest.

I suspect you encountered a separate hd/analog transmission system which had the analog go south. If you're familiar with the system, you know that Analog and Digital are often times NOT run through the same transmitter or antenna. Such probably occured here.

Just like two lights in your living room, at times, even if you want them both on all the time, occasionally one will not work right.

We've heard endless ridicule about this happening to Digital. I also happens to Analog. Occasionally EVERYTHING goes off the air...

A more interesting question might be...

Does the seek or scan fuinction of an HD radio require an analog carrier to work? It SHOULDN'T..

But I can see how Mickey Mouse design would allow it to work that way. TODAY, who would notice?

Tom Wells could probably speak to this better than me, but if I were a designer, I can see how the "Seek" and "Scan" would be a copy of today's analog methodology. And NOT work with HD.

Not very good design. Just like those $0.50 AM radio sections.

Bad idea all around...

Clouseau
 
clouseau said:
A more interesting question might be...

Does the seek or scan fuinction of an HD radio require an analog carrier to work? It SHOULDN'T..

But I can see how Mickey Mouse design would allow it to work that way. TODAY, who would notice?

Tom Wells could probably speak to this better than me, but if I were a designer, I can see how the "Seek" and "Scan" would be a copy of today's analog methodology. And NOT work with HD.

Not very good design. Just like those $0.50 AM radio sections.

Bad idea all around...

Clouseau
Click to expand...

Yes I also thought that that was what engineers would perhaps have an answer to, the fact that the HD radio did not "know" that the HD signal was still broadcast, very strange and I wonder if all HD radios are built like that, if they need the analog signal for the scan function.
 
It's cool to know at least that SONY unit (which is the only HD Radio I own now, since it's a pretty nice radio) can receive digital only stations, even if they have to tuned manually, a minor deal to me. Should radio ever become IBOC only (I hope not), at least I could still listen.
 
In the AM digital-only version, a small "vestigal" carrier is still necessary for the sidebands' to reference against.
I suspect SOMETHING still had to be present for the digital sidebands to reference in the FM version, but the frquency deviation may be so small as to show "no signal" in analog. In any case, the power in the sidebands must be so large by comparison that the scan fucntion is not going "slow" enough to notice the tiny carrier between the digital sidebands. D'oh!
 
I may be wrong because I dont work with IBOC, but it seems to me that early in the game several stations used a separate TX and antenna for the digital signal. In fact it seems I also recall some even transmit the digital from a different location. I may be all washed up and should be sent back to my 3 tower in line DA but it could be that the analog tx was off and the digital still on....
 
Here is another data point for thought. I've built a number of HD FM stations, starting a few years ago. One of them uses a dual transmitter setup with a 8db injector. Analog power is 4KW tpo, HD power is 215 watts tpo. We lost the analog transmitter from a tripped circuit breaker, and the HD stayed on, with the reject load absorbing a bit of the load. I lived about 90 minutes from the transmitter at the time, and drove in to investigate. On the way in, my JVC HD car radio had a perfect HD signal (as usual) all the way in. Because the radio was set with presets, I did not think to check (at first) if it would lock without an analog carrier. BUt within ten miles of the site, I though that it would be interesting to see if it locked on via the seek feature. And it did, just like normal.
I also had a Blaupunkt analog radio in the dash, and the seek function found the HD carriers as well. On the analog radio, I used the tune feature and IBOC noise was fairly quiet at center channel, and noisier on the adjacent, pretty much as expected.
I am fairly sure that the seek feature is radio-receiver dependent. At least according to my informal test.
 
Status
This thread has been closed due to inactivity. You can create a new thread to discuss this topic.


Back
Top Bottom