Re: [IRCA] [NRC-AM] "HD" DX?

[Barry McLarnon <bdm@xxxxxxxxxx>]

On Tuesday 09 January 2007 20:21, Tom Ray wrote:
> At 50KW, the average power is about 1,500 Watts.  I highly doubt it's a
> power saving issue.  The regulations say you MUST turn it off at sunset or
> 6PM, whichever is later, providing you are licensed to be on the air at
> that time.  And yes, we shut off this month at 6PM..we're not leaving it
> on.  We follow the regulations.

You're about 3 dB down there, Tom - according to the iBiquity specs, a 50 kW 
station would have an average digital power of about 2940 Watts.  See
http://topazdesigns.com/iboc/AM-IBOC-Parameters.html for the gory details.

That said, I'm sure you're right that early digital shutdowns are not done to 
save a few bucks on the power bills.

I checked around earlier, and found that a surprising number of the IBOC 
stations that I can hear (only by skywave, of course) are shutting off the 
digital signal earlier than they need to.  When I first checked at 1615, I 
found that WCBS, WABC and WGY already had their IBOC off, nearly two hours 
before they're required to shut it down.  I have no way of knowing whether 
they had it on earlier in the day, but they've all been observed with IBOC on 
recently.  WFAN shut theirs off at 1700, an hour earlier than necessary.  WJR 
and WHAS also did not run IBOC until 1800 - both had it off when I checked at 
1745.  And the Chicago clears (WGN, WSCR, WBBM) all appeared to shut their 
IBOC off at 1745 (all times are EST), which is an hour and 15 minutes early.
All of these stations are NDA and have no sunset pattern change, so it's not a 
matter of the IBOC control being tied to that.  I can only surmise that they 
are choosing to shut down early in order to limit interference to other 
stations (some of which, of course, would be under the same ownership as 
these IBOC biggies).  Another reason might be to hide the fact that digital 
coverage can take a big hit after dark.  Anybody got a different theory?

Barry

-- 
Barry McLarnon  VE3JF  Ottawa, ON
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