Hi all, I often use my radio as a noise/sleep machine by tuning it to the HD sidebands. What I've noticed is that not all HD sidebands sound the same. For a given station, sometimes the upper sideband sounds low pitched, more pink noise like hash, while the lower sideband sounds like a raspy white noise with picket fencing dah dah dah within the noise itself or vice versa. Some stations' upper and lower sidebands they do all sound the same like mosquito buzzing, some not so much. Can anyone tell what's causing the sounding difference between the sidebands for FM or even AM? Thanks all.
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Upper and lower sidebands sound different
- Thread starter billy2047
- Start date
Yes you have heard correctly, Asymmetrical Sideband operation for HD Radio now is a reality.
There are situations where the power of the digital signal can be increased on one side of the analog carrier frequency, depending on FM stations adjacent to the HD station analog frequency. However, the nominal power of the sideband that is not Increased in digital power may not be decreased below the minimum, which is 1% of analog ERP. The sideband that can be increased, can be increased to up to 10% of analog ERP.
No mention if Asymmetrical operation would be allowed on AM, though that would seem to be desirable for that band as well.
I'm only guessing that the reason one carrier may sound different is possibly that the stronger sideband allows you to hear more of the multiple carriers.
www.radioworld.com
There are situations where the power of the digital signal can be increased on one side of the analog carrier frequency, depending on FM stations adjacent to the HD station analog frequency. However, the nominal power of the sideband that is not Increased in digital power may not be decreased below the minimum, which is 1% of analog ERP. The sideband that can be increased, can be increased to up to 10% of analog ERP.
No mention if Asymmetrical operation would be allowed on AM, though that would seem to be desirable for that band as well.
I'm only guessing that the reason one carrier may sound different is possibly that the stronger sideband allows you to hear more of the multiple carriers.
FCC Now Accepting Asymmetric Digital FM Sidebands - Radio World
The FCC has announced that asymmetric FM HD Radio operation may now be initiated through a simple form notification.
www.radioworld.com
I'll take it this also explains the reason some analog AMs sound crispier when tuned off-frequency in one direction versus the other? I have noticed this with digitally tuned receivers, for what it's worth, that permit 1 kHz tuning steps.
For example, 636 kHz and 644 kHz will exhibit equal boosts in highs relative to 640 kHz, but with another station, 1016 kHz and 1024 kHz will have very different audio frequency response curves -- one might even be slightly duller sounding than 1020 kHz itself. I have always assumed that an antenna Q that wasn't centered directly on the station's frequency, or with one shoulder that was steeper than the other, had to be the reason for this, but have never known for sure.
Another reason is audio when mixed with a carrier (that is what AM basically is) produces a product that is off-set from the carrier. For instance, a 1 kHz tone modulating a carrier will produce a product of the carrier frequency + and - the 1 kHz tone. Therefore, if you are tuning slightly above or below the carrier frequency you will hear higher, crisper audio.
They have adjustable white/pink noise makers for sleep now. I have one and it gives me flashbacks of waking up at 2am to the white noise of the TV after the station signed off for the night.
I live in an problematic area where HD sidebands often clash with first-adjacent Canadian signals. So I don't have the luxury of just using the HD sidebands on an analog radio like you do for your white noise.
I live in an problematic area where HD sidebands often clash with first-adjacent Canadian signals. So I don't have the luxury of just using the HD sidebands on an analog radio like you do for your white noise.
And the reactance at equal distances from the carrier will not be symmetrical. So to the "left" of the carrier on AM, you may have a considerably different j than to the right of the carrier frequency. Add in receiver bandwidth and all kinds of stuff can happen.