[opendtv] Re: FCC on revitalizing the AM band

  • From: Cliff Benham <flyback1@xxxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Sun, 25 Oct 2015 22:13:22 -0400

Bert, I completely disagree with all you say below.

You probably don't know much about the technicalities of radio broadcasting.
I've been doing it since around 1964. To learn about HD radio read the following:
https://en.wikipedia.org/wiki/HD_Radio

See interspersed replies...

On 10/25/2015 8:33 PM, Manfredi, Albert E wrote:

Cliff Benham wrote:

The addition of HD radio signals to the AM band has rendered it
practically useless. I can no longer listen to WLW, Cincinnati,
and other power house and previously CLEAR CHANNEL stations
because the HD digital noise from adjacent frequencies blankets
the clear channel frequencies.

At night? I thought use of HD Radio in the AM band was banned at night,
although maybe that decision got reversed while I wasn't looking.

HD radio is 24 hours a day.


Why not turn off analog AM, replace it with HD Radio in that band, and retain
all the clear channel stations with HD Radio. Then you can do your DXing in
digital, and listen without the 10 KHz squeals, the abysmal sound quality, and
all the rest. Longwire antennas would work for HD Radio too.

HD radio is limited to 17% of the radiated power of standard AM. You cannot pick up an AM HD signal much farther than the local footprint, certainly not from a state or half the couotnry away. HD requires a 20 KHz channel bandwidth which encroches into the two adjacent AM channels making their reception practically impossible because of the digital noise that interferes with them.


The FCC wants only to get rid of standard AM broadcasting so it
won't have to deal with the technicalities involved in
directional signals [because there are more lawyers at the FCC
than there are competent RF engineers] and AM broadcasters want
to make the coverage of AM stations smaller so there is no way
listeners can hear a signal outside of their local markets.

The FCC is only talking about minor tweaks, while retaining oldfashioned AM.

Bert THESE ARE NOT MINOR TWEEKS!

I would expect that AM broadcasters would want their signal to travel as far as
possible, unless, like you suggest, ratings companies and/or advertizers get on
their case. I wouldn't know.

If you think about market protection in terms of satellite TV you will recall that one time it was possible to watch the NBC affiliate in San Francisco here in PA, or the Chicago ABC affiliate here in PA as well. Then things changed. The FCC passed rules preventing me from watching any network affiliate that wasn't from the market where my sat receiver was located.
[I wonder what factions lobbied and influenced the voting on THAT?]


I own several HD radios both AM and FM and although I live no
more that 20 miles from the edge of the Philadelphia market, I
cannot receive but one or two weak crappy signals, even with a
roof mounted antenna.

Well, IIRC, in the FM band, the HD Radio signal has to be 23 dB below the
analog. And in the AM band, something more preposterous, like 35 dB below the
analog. Plus, a problem with HD Radio reception from far away, during this
hybrid mode operation, is that all of the digital signal is in the guardbands.
So it could easily be interfering with some other FM or AM stations in other
nearby markets.

Yes, the HD signals are intended only to be received within the markets they are located, hence the lower power alloted to the HD signals.

Regardless, the HD signals interfere with adjacent channel stations and preclude their reception.


In the AM band, if analog AM goes off the air, the HD Radio signal would be
back down to 10 or 9 KHz channel width, so the result should be the same kind
of channel discipline as there was previously.

Again, read the link above.


AM is just too primitive, Cliff.

That's your opinion, with which I violently disagree.


It's time to either make effective use of that frequency band for radio,

Bert, it is already AM radio that can be heard across the country without doing anything to it.

or assign it to something totally different, like time signals.

Time signals are already available at 2.5, 5, 10,15 and 20MHz from WWV in Ft. Collins, CO.

And hobbyists can always use low power HD Radio to AM converter boxes, which
would most likely appear on the market for them?

Bert

I'm a hobbyist but also a FCC licensed engineer from 1965 forward.

Do you realize that at one time WLW Cincinnati broadcast at a power of one-half a Megawatt?

500,000 watts, a signal that blanketed the lower 48 with good reception for news and current events. During WWII and the cold war the government paid WLW to keep that 500,000 watt 'RIG'
operational, ready to go on the air momentarily in case of a national emergency.

I have 28 radios, all of which receive AM and many of which also receive longwave, shortwave and FM transmissions.

The proliferation of HD radio has decimated regular AM and FM reception with most of them, and as I have mentioned previously the HD radio receivers don't begin to receive nearly as well as
they do.

HD radio is not doing the job it was promoted as being capable of. Many stations that installed HD equipment have removed it and returned to standard AM and FM transmission because of the poor
sound quality, reduced signal coverage it causes as well as interference to adjacent stations.

I hope HD radio goes away and that AM and FM broadcasting will continue on as they were prior to 2002.

Cliff Benham

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