[BC] Re: IBOC secrets and my opinion

[WFIFeng@aol.com]

In a message dated 03/27/2007 10:27:43 PM Eastern Daylight Time, 
bdm at bdmcomm.ca writes:

> > 50Kw station on 1000 with IBUZ is transmitting 500 watts (average) of 
> white
>  > noise on 990 and on 1010. Stations on *those* frequencies are going to 
get
>  > trounced in their hometowns by the skywave coming from the 1000 station's
>  > IBUZ!
>  
>  Bzzzzzt!

Hello, Barry. :) I was thinking of what you said before, when I enclosed the 
word "average" in parentheses, above. Perhaps I should have said "approximate, 
measured"? ;)

Just as an example, WOR is a 50Kw station. They are a top-notch facility, so 
they make a good example of how the system can work when done right. With a 
calibrated FIM, I was getting their main carrier at 10mv/m in West Haven,CT. To
 
either side, I measured 1mv/m of "hash". That's 10% of the analog signal, IE: 
500 watts. That's where I got that figure.

>  Once again, I must point out that the 50 kW IBOC station puts, not 500 W, 
> but 1.3 kW of digital power on each first adjacent 

I remember you saying this the last time the power levels of the hash 
generators were being discussed, and you make the case very well. I'm certainly
 not 
"arguing" or even challenging your numbers, as I believe you 100%. :) I'm only 
saying "500 watts" because that was what I was able to actually observe with a 
fairly commonly-available and calibrated test instrument. Perhaps if the FIM 
had a wider bandwidth, it would have shown more than 1mv of "hash". 1.5mv, 
perhaps?

>  Experience with the DRM 
>  system has shown that, in terms of causing interference, an OFDM digital 
>  signal like IBOC is equivalent to an analog signal having carrier power at 
>  least 6 dB higher than the average digital power.

Effectively, then, 4mv/m of analog equivalent signal! Wow!

>  That means, in effect, 
> the 50 kW AM station is deploying two new 5 kW stations on its 1st adjacent 
>  channels. 

5Kw would have given me 3.16 mv/m, based on 10mv for a 50K signal.

> Stand back... it ain't gonna be pretty.

It already is not. I have heard the horrendous interference between winter 
sunset & 6pm, myself. I'm going to have to do some more tuning-around at night,
 
once the floodgate opens and the hash generators start running all night. 
Their skywave will be obliterating some local coverage areas, for sure. "Stay 
tuned..." (for as long as you can stand it.)

Willie...





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