Analog off, HD on, and it still decodes.

[tomservo]

OK, I know there's nothing special about this, but I happened to capture it on video just for giggles. Local Clear Channel country station "95 KSJ" went off air this morning, presumably to do maintenance or something, but left the HD on. So while most radios only heard static, the Insignia HD radio actually decoded the sidebands without the analog present. Kinda weird hearing it go from static to music! This is the second time I've heard WKSJ doing this on the weekends.

The video's on The Tube of Yous, and runs only one minute.

Strangely, the scan on both my Insignia and another analog only radio was suddenly stopping on both sidebands while the analog is off, like they were legit signals. But the Insignia wouldn't decode HD unless it was manually tuned to the center frequency 94.9. (And for the DX enthusiasts, you hear a faint hint of WFLF from Panama City on 94.5 and full signal WZNF from Biloxi on 95.3. Good little radio!)

 

[spunker88]

With the absence of a higher amplitude analog signal, the radio is seeing the two HD sidebands as separate signals and seeking to them individually.

Its weird that HD Radio was never designed to work in a non analog environment, maybe if the sidebands were brought in to the analog frequency, it would seek correctly. But would existing HD Radios be able to decode that? Also would they know to not play the analog noise and instead stay silent until HD locks? It seems on this radio in the absence of an analog signal, the radio still plays analog before locking in HD.

 

[iyiyi]

OK, I know there's nothing special about this, but I happened to capture it on video just for giggles. Local Clear Channel country station "95 KSJ" went off air this morning, presumably to do maintenance or something, but left the HD on. So while most radios only heard static, the Insignia HD radio actually decoded the sidebands without the analog present. Kinda weird hearing it go from static to music! This is the second time I've heard WKSJ doing this on the weekends.

The video's on The Tube of Yous, and runs only one minute.

Strangely, the scan on both my Insignia and another analog only radio was suddenly stopping on both sidebands while the analog is off, like they were legit signals. But the Insignia wouldn't decode HD unless it was manually tuned to the center frequency 94.9. (And for the DX enthusiasts, you hear a faint hint of WFLF from Panama City on 94.5 and full signal WZNF from Biloxi on 95.3. Good little radio!)

Real question here is: What does 94.9 sound like when tuning through the frequency on an analog radio with 94.9 HD operating and 94.9 analog off the air?

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[w9wi]

With the absence of a higher amplitude analog signal, the radio is seeing the two HD sidebands as separate signals and seeking to them individually.

Its weird that HD Radio was never designed to work in a non analog environment, maybe if the sidebands were brought in to the analog frequency, it would seek correctly. But would existing HD Radios be able to decode that? Also would they know to not play the analog noise and instead stay silent until HD locks? It seems on this radio in the absence of an analog signal, the radio still plays analog before locking in HD.

There is a full-digital (with no analog) mode defined; indeed, there are hot discussions elsewhere on the site about a planned test of the *AM* full-digital mode. *I believe* pilot tests have been made of full-digital *FM* at low power.

Whether existing HD receivers would receive a full-digital signal I don't know, but I'd be VERY surprised if they didn't.

There are a number of examples of DXers receiving the digital signal of a distant station on the same frequency as an analog-only local station.

 

[tomservo]

Real question here is: What does 94.9 sound like when tuning through the frequency on an analog radio with 94.9 HD operating and 94.9 analog off the air?

I can answer that as well, since I first stumbled upon it with an analog radio. 94.7 and 95.1 both sounded like really strong, uniform static (ha, oxymoron!) and pegged the meter out signal wise. 94.9 actually sounded like much quieter static, and the signal meter went back to 0 when turned right in the center. But it quickly sloped back up with the slightest mid-tune, with an accompanying louder woosh of the sidebands.

 

[iyiyi]

Real question here is: What does 94.9 sound like when tuning through the frequency on an analog radio with 94.9 HD operating and 94.9 analog off the air?

I can answer that as well, since I first stumbled upon it with an analog radio. 94.7 and 95.1 both sounded like really strong, uniform static (ha, oxymoron!) and pegged the meter out signal wise. 94.9 actually sounded like much quieter static, and the signal meter went back to 0 when turned right in the center. But it quickly sloped back up with the slightest mid-tune, with an accompanying louder woosh of the sidebands.

Excellent! You heard an HD operating in hybrid mode sans analog carrier. The "uniform static" is no oxymoron but is a deliberate randomization of the digital data to ensure no heterodyne of data occurs.

The zero center tune on the analog demonstrates why digital carriers are run in hybrid mode and how they cancel their interference to the analog signal. A pure digital HD would be one continuous (but much lower) increase in background noise that shouldn't peg the meter.

I believe that HD also now has the capability to actually run completely different digital data on the individual sidebands. I haven't seen anything in NRSC-5-C that currently authorizes this, however.

You will know a pure digital HD signal when you hear one!

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