"HD Radio Digital Carrier Power Calculations"

[700WLW]

"HD Radio Digital Carrier Power Calculations"

http://www.am-dx.com/iboc_power.htm

I am a software, not broadcast engineer - maybe, some of you could spell this out in layman's terms. Sorry, I just noticed, that this was written by Clear Channel, so is probably BS...

 

[radioskeptic]

I just checked the above link, and there's no date. Can you tell us when it was written?

 

[700WLW]

I just checked the above link, and there's no date. Can you tell us when it was written?

http://groups.google.com/group/ba.b...st&q=iboc_power&rnum=1&hl=en#3f3d7c8f5a01aeda

 

[SUPERCASTER]

"HD Radio Digital Carrier Power Calculations"

http://www.am-dx.com/iboc_power.htm

I am a software, not broadcast engineer - maybe, some of you could spell this out in layman's terms. Sorry, I just noticed, that this was written by Clear Channel, so is probably BS...

What all this means is that not only does HD AM on the host station cut the analog fidelity in half, it also adds 2400 watts of iBuzz (for a 50kw station) or -13 db iBuzz noise to the parent HD stations analog audio, and severely jams other adjacent channel stations.

Self interference to the host analog station is 3 dB worse, since both
sidebands are present within the host envelope. The total RMS energy in
the two digital sidebands, combined, is 13.2 dB below unmodulated
carrier within the host channel envelope, or 2400 watts for the 50 kW AM
example.

 

[dumber than a box of hair]

What all this means is that not only does HD AM on the host station cut the analog fidelity in half, it also adds 2400 watts of iBuzz (for a 50kw station) or -13 db iBuzz noise to the parent HD stations analog audio, and severely jams other adjacent channel stations.

Self interference to the host analog station is 3 dB worse, since both
sidebands are present within the host envelope. The total RMS energy in
the two digital sidebands, combined, is 13.2 dB below unmodulated
carrier within the host channel envelope, or 2400 watts for the 50 kW AM
example.

They took the emissions mask, designed to keep stations from interfering with each other and never meant to contain substantial RF energy more than about 10 kHz from the center frequency, and stuck the digital carriers inside it. The result, in today's crowded and noisy AM band, was quite predictable.

 

[Tom Wells]

A good layman's analogy is the elevator. The design max is for 12 people, let's say.
Most of the time the elevator carries 2,3,or 4 people. Once in a great while, 14 people crowd in, and not all of them are at the
theorectical weight, so the elevator works fine. It is briefly at its limit. This is analogous to the occcaisional once every 10 minutes
overmodulation event. The average occupancy is 3.
If the manufacturer had wanted to design an elevator for 14 people, it's max limit would need to be 20 people.
The IBOC equivalent is that the elevator that normally carries 3 people is filled with 14 people ALL THE TIME, EVERY TRIP.
Even during the time when there would be no people (no modulation), the IBOC load of 14 people is ALWAYS there.
This means that the amount of power used must be calculated with the 14-person load, not the theoretical middle-ground
of a 6 person load. Ibiquity basically said that they never expected the integrated average of the power spectral distrubution was
so "full" as it really is, so they had to redefine the stated power present in the sidebands.
Sorry if you can't hear favorite station as well anymore. Our bad, have a nice day. Sorry about the hiss, too.
real sorry....

 

[700WLW]

Thanks guys - hope this gave you some new data !

 

[SUPERCASTER]

I just checked the above link, and there's no date. Can you tell us when it was written?

http://groups.google.com/group/ba.b...st&q=iboc_power&rnum=1&hl=en#3f3d7c8f5a01aeda

The article mentions an exellent engineer, Barry McLarnen, who wrote the only comprehensive independent engineering study of HD AM and FM. It was serialized in "Radio World" magazine in 2005.