B96 boosted HD power by 4X

[briankay]

I just realized B96 had boosted their digital power by 6 dB (4 times) according to the FCC application search. http://licensing.fcc.gov/prod/cdbs/pubacc/prod/app_sear.htm
Their digital ERP from the Sears tower is 131.4 watts according to their May 19th FCC filing. The transmitter output power for analog and digital is 9600 W and 384 Watts respectively, which is presumably, then reduced by the antenna system, probably a single bay, circular polarization, which usually reduces the ERP, but with overall improvement in mobile and indoor reception. From what I can gather, they also made their antenna pattern fully omni-directional which meant a reduction to 3300 watts analog to protect nearby first adjacents. I definitely see the improvement in HD digital reception, 40 miles west of Chicago amongst other places.

 

[JeremyAndrews]

I know I sound like an idiot here, but what should I put in that search form to look that up?

On a side note, if any station needed a power increase on their IBOC, it was B96. Horrible, even in downtown Chicago.

 

[briankay]

It's well buried in there. In fact I could find it when I tried the second time. Here's the direct link to the B96 digital notification

http://licensing.fcc.gov/cgi-bin/prod/cdbs/forms/prod/getimportletter_exh.cgi?import_letter_id=18902

Note you change the last digits in the link above to see perouse through other recent digital notifications as it seems to be difficult to find them through the FCC search system.

 

[radiotower40]

That was a good question, thanks for the answer Brian. I had trouble finding that too.

I have another question if you have an answer. Is there anywhere you can find the coverage
maps for the digital signals on either band?

 

[briankay]

Here's a estimate of best case HD coverage with the 6 dB increase (B 96 is only 3000 W analog/120 W digital after digital increase) in the absence of first adjacent stations of which there are a few in the region. Blue or darker should be relatively good. Light Blue = probable intermittent HD reception
http://i765.photobucket.com/albums/xx297/briank101101/Tech1/B96_HDcoverageEstimate.jpg

Other Chicago stations should have better digital coverage after digital power increases due to their high power allowance compared to B96.

Predicting HD coverage just like analog would be relatively straight forward in the absence of co-channel and adjacent channel interference from other FM stations which can vary considerably due to various weather conditions for example. (e.g. troposhperic ducting) however this is a great FM coverage prediction site http://lrcov.crc.ca/main/ (free registration) with which you can derive the HD FM coverage given the fact that HD reception can received with as low as 40 dBu of FM signal in the absence of at least 1 first adjacent. So for B96 if 96.1 and 96.5 have no receivable signal at your location, the 45 dBu signal level should apply with a good HD tuner. Remember signal level can vary dramatically even by moving a few yards.

Remember the FCC 54 dBu or 60 dBu (50/50) signal contours assume an antenna at 30 feet (9 meters) above ground, which can drop as much as 20 dBu at the average height of a car antenna (1.5 meters above ground) with a 31" vertical whip. If you have a short or cosmetic car antenna, you can take quite a few more dBu off the signal level that will reach your FM tuner.

 

[briankay]

Just to add, in an all digital world the high power first adjacent analog signals would no longer interfere with the digital carrier and HD reception would greatly improve. The area where the analog signal resided would be replaced with lower power digital carriers much lower in absolute level which would greatly reduce 1st adjacent interference. This is where HD radio would really shine. They would also probably further bump up the HD power significantly in the absence of analog thus further improving reception quality. Most of HD radios bad rap as reception goes has to do with trying to coexist in the analog band. Put it this way if digital was first, analog would never be allowed after the fact due to its big interference impacts on the IBOC digital carriers.