NBC Boston info

Paul B. Walker, Jr. walkerbroadcasting@gmail.com
Tue Nov 8 12:04:54 EST 2016

I've got an 18 watt digital signal on RF Channel 10 here and all I need to
see all 4 streams of programming is a paperclip on the back of my tv! :)

On Tue, Nov 8, 2016 at 12:01 PM, M.Casey <map@mapinternet.com> wrote:

> Agreed on the technical points.  A 3db difference in power ratings makes
> sense.
> The differences between digital and analog and a poorly designed FCC
> formula for a well designed digital system that over-rates digital signal
> expectation against old analog limits force us to deal with a so-called
> apple and orange comparison.
> ---The example:
> "WGBX's analog was at 1100 kW.  Its digital is now
> 500 kW.  That's slightly more than 3 dB of difference.  They're basically
> equivalent when you account for the difference between peak and average
> power."
> ---agrees with my point:
> "most digital TV stations should have 20-50% of their analog power to
> effectively duplicate their coverage on digital"
> 44's digital power is 45.4% of it's analog.
> Of course, there's the problem of VHF stations moving to UHF. After
> initial problems on VHF, and due to the looming repacking, and the FCC
> letting up on power limits as in the LA example below, we may be seeing a
> reversal to VHF to UHF migration to a UHF to VHF migration. Like LA, If
> Boston Channel 7 was allowed 115kw instead of 11.8kw on RF7, they might
> find it beneficial to move their digital signal back to RF7. And, if Boston
> stations moved back to both VHF hi-band and low-band allocations using
> 30-40% of analog power, then many of those folks in mountainous areas like
> Central & Western Worcester County would get back the OTA TV service they
> lost in 2009.
> Maybe when TV was new in the 1940's and 1950's it was a factor, but I
> disagree that any significant segment of analog viewers after the 1960's
> put up with poor signal. I don't know anyone that did. If they got a poor
> signal they either got a better antenna or an outside antenna or bought
> cable, if cable was available. There are thousands of viewers that have
> been dis-enfranchised from OTA TV because of the poorly designed FCC power
> limit scheme for channels 2-13.
> The bottom line is the question for the public:
> After the conversion to digital, can the viewers still receive most of the
> same stations using the same or similar antenna they had used with analog?
> In the cities and suburbs, probably so, farther out in the country,
> probably not.
> If not, then digital power needs to be increased, like the example of Ch
> 11 & 13 in the Los Angeles market, whose original digital allocated power
> was 5% of analog (11,800w), and have now been increased to more than 35% of
> analog (115,000-120,000w) in order to more closely duplicate their analog
> coverage.
> Mark
> -----Original Message----- From: Trip Ericson
> Sent: Monday, November 07, 2016 2:43 PM
> To: M.Casey
> Cc: A Joseph Ross ; Boston Radio Group
> Subject: Re: NBC Boston info
> As an engineer, I disagree because you're comparing apples and oranges.
> Analog power was peak power.  You only hit 5000 kW analog when a solid
> black picture was being transmitted; the rest of the time, the signal was
> lower than that.  ATSC digital power is average power.  Since ATSC's peak
> to average ratio is about 3-5 dB (with the maximum, very rarely, being 7
> dB), the typical peak power of a 1000 kW ATSC signal is closer to 2000-3000
> kW.  That's a 3 dB difference on UHF.
> And then that doesn't take into account the difference in receive
> thresholds.  A perfect digital decode requires an SNR of 15 dB, give or
> take a bit of margin to account for fading.  A decent analog picture
> required something like 30 dB SNR, and a perfect picture was closer to 50
> dB SNR.  So the power has gone down, at best, 6 dB on UHF, but the margin
> for reception has dropped at least 15 dB, depending on how clear you want
> to make the picture before calling it acceptable.
> The real difference is that people were willing to put up with very poor
> pictures in analog and low-VHF was more forgiving of rough terrain.  Even
> if you ramped up the power and put digital stations back on low-VHF, many
> of those people still wouldn't have service because the signal was never
> that great to start with.
> Here's a good example.  WGBX's analog was at 1100 kW.  Its digital is now
> 500 kW.  That's slightly more than 3 dB of difference.  They're basically
> equivalent when you account for the difference between peak and average
> power.  An outdoor antenna should receive WGBX, notwithstanding
> interference from other stations, out to at least Webster, Charlton,
> Rutland, and Ashburnham, notwithstanding a few really serious
> terrain-caused holes, and see increasing terrain blockages west of that.
> - Trip
> www.rabbitears.info
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