Dumbed down consumer electronics: Adding DTV channels

[Joerg]

I seem to recall that you're on the left coast and don't get
thunderstorms
and the like, but I have noticed that here in the Mid-Atlantic, that
very wet weather (not necessarily thunderstorms) can render even
the strongest local DTV channels unwatchable. With the exact same
antenna on analog stations there was no noticeable degredation
(except for nearby lightning) at all in the same weather conditions.

My pet theory is some sort of multipath from wet tree leaves but I
have no
scientific evidence at all!

Yup, you got it. When clouds roll in it's all over with DTV while analog
was just fine. I guess this is called progress :-(

 

[Paul Keinanen]

I seem to recall that you're on the left coast and don't get
thunderstorms
and the like, but I have noticed that here in the Mid-Atlantic, that
very wet weather (not necessarily thunderstorms) can render even
the strongest local DTV channels unwatchable.

Digital television is typically operated only a few dB above
threshold, producing a "perfect" image. However, if the signal level
drops only 2-5 dB, the signal can be below thresholds for extended
period of times and the picture is useless.

With the exact same
antenna on analog stations there was no noticeable degredation
(except for nearby lightning) at all in the same weather conditions.

If the normal signal to noise ratio is say 50 dB, you would hardly
notice, if it drops to 45-48 dB.

At least in Europe, the digital transmitter ERP power was initially
10-20 dB below the analog TV synch tip ERP power, however, in order to
maintain sufficient fade margin, the -20 dB settings are now out of
the question.

My pet theory is some sort of multipath from wet tree leaves but I
have no
scientific evidence at all!

The refractive index for vacuum is by definition n=1 and for air
n=1.0003xx. In propagation calculations, the relative refractive index
N is often used and it is the number of ppms above 1.0. At sea level
N=300 is quite common.

The relative refractive index depends on the "dry term", which depends
of air pressure, temperature and height and the "wet term" depending
on temperature and amount of humidity.

The relative reflective index in general drops at higher altitudes and
reaching N=0 in space. The globally annual average gradient is -40/km,
while at some places it can be -30 /km and others up to -150/km (in
desert areas in particular). For a particular place and a particular
altitude layer, the instant gradient can vary even more than this
during the year.

The reflective gradient is responsible for slightly bending the radio
waves towards the ground and hence, the radio horizon is slightly
further away than the optical horizon. For N=-40/km, the radio horizon
is about 15 % further away than the optical horizon. For N=-157/km,
the radio waves exactly follow the curvature of the earth and the
signals could travel thousands of kilometers as long as the gradient
remains stable.

In practice any layer of warm/cold and/or wet/dry masses at some
altitude along the signal path will alter the gradient, sometimes
bending the signal slightly upwards above the receiver and into the
space. Sometimes it is bent slightly more downwards than normally and
strong signals are available just behind the horizon.

With a strong gradient, the transmitter signal hits the ground in
front of the receiver and is reflected from ground up to the space and
is lost. With very strong gradients (N<-157/km), ducting will occur,
the signal reflected from ground will be bent back towards ground at
some other place to be reflected again from the ground. Depending on
the location of the receiving station, it might be just were the
ground reflection occurs and a strong signal is obtained or it might
be between the location of two ground reflections and the signal
passes over the receiver station.

Since the atmospheric conditions vary constantly, so will the signal
strength vary with a typical rate of some hours "slow fade". This kind
of fade affects all frequencies equally (at least the whole UHF TV
band) as is known as "flat fade".

However, if the receiving antenna also gets local reflections from
ground and nearby buildings, there are also going to be multipath
(fast frequency selective) fading atop of the slow fading, since even
minute variation in the gradient will cause variations in the
amplitude and phase of both the direct and reflected multipath signal,
causing fast variations in the frequency selective fading, when those
are combined in th receiver antenna.

The fading that took out all channels for an hour or two was clearly
slow flat fading due to variation in the refractive gradient.

Failing to find all channels at once in a program scan looks very much
like a fast frequency selective multipath fading.

In general, the signal from a distant station are often strongest very
early in the morning, when the ground is still very cold and some
inversion layers have been formed. Try to scan for the channels early
in the morning, when the average signal levels are higher than during
a hot evening.

 

[David Lesher]

I seem to recall that you're on the left coast and don't get
thunderstorms and the like, but I have noticed that here in
the Mid-Atlantic, that very wet weather (not necessarily
thunderstorms) can render even the strongest local DTV channels
unwatchable. With the exact same antenna on analog stations
there was no noticeable degredation (except for nearby
lightning) at all in the same weather conditions.

Note that many DTV channels are a) on different frequencies
b) from different transmitter sites/antennas with c) different
power levels than with NTSC.

That said, in DC "7" and "9" DTV are on RF 7 & 9. But there's
been a major effort to understand why VHF freq's have
delivered so much worse ASTC propagation than was there under
NTSC. Multiple stations have gotten temporary FCC authority to
raise power levels. One suspect is the cheap CECB {couponed
converters} suffer from front-end desensitization by FM
broadcasters.

 

[JosephKK]

How do you know? Hint: We have no HOA whatsoever. That would have been a
reason for me not to buy a house here. I told our realtor back then: No
HOA, no Mello-Roos taxes, and I don't want furniture to rock when I jump
on the floors (the "Joerg" test, as she called it).

Sorry, must have confued you with another living in the hills with
ATSC reception problems and an ugly HOA.

Besides, the mast won't help. If I had four masts half a mile apart,
maybe. Yesterday the usual happened, none of the news channels made into
into this area, they all pixelated out shortly before 10:00pm. Meaning
lots of people in a middle-class neighborhood haven't seen any of the
ads, meaning ...

Kind of wierd to have AM/PM type fading in VHF and UHF bands. The
multiple antennas would point in very different directions. Not
single channel path diversity but per channel group separated antennas
pointed at the best signal (usually right at the transmit antenna but
not always).

Kids out here would respond that TV is so last week, get on the Internet
and watch news there because it always works.

And Internet TV has total tracking (no privacy) and many times the
ads.

 

[Joerg]

[...]

Besides, the mast won't help. If I had four masts half a mile apart,
maybe. Yesterday the usual happened, none of the news channels made into
into this area, they all pixelated out shortly before 10:00pm. Meaning
lots of people in a middle-class neighborhood haven't seen any of the
ads, meaning ...

Kind of wierd to have AM/PM type fading in VHF and UHF bands. The
multiple antennas would point in very different directions. Not
single channel path diversity but per channel group separated antennas
pointed at the best signal (usually right at the transmit antenna but
not always).

Ok, the next step would be to buy a motorhome and drive 100ft farther,
see if it works there. Then back up again when the clouds have passed

There comes a point when the effort to obtain a signal just ain't worth
it anymore.

And Internet TV has total tracking (no privacy) and many times the
ads.

Kids are pretty smart these days. They can tune out any ad they want and
if tracking would ever be a concern there's proxy servers, anonymizers
and all that. But I don't need that stuff.

 

[JosephKK]

Content is what it's all about. I know next to nothing about HD. Does
it work in tunnels and underpasses? If so, subscription HD might be a
viable answer.

...Jim Thompson

In long tunnels there are often AM and FM repeeater systems, as well a
repeater systems for local emergency responder channels. Simple
underpass are not so equipped.

http://www.gl.com/consulting_masstransitletter.html

 

[JosephKK]

Content is what it's all about. I know next to nothing about HD. Does
it work in tunnels and underpasses? If so, subscription HD might be a
viable answer.

...Jim Thompson

Oops, forgot to mention, while rebroadcast systems are possible for XM
and Sirius; State agencies often refrain from providing them because
of the propritary modulation and fee for service aspects. They may
allow the statellite providers to install and maintain their own
systems. In case you are intersted they operate from 2160 to 2180
MHz.

 

[Paul Keinanen]

This is a typical flat (broadband) fading case caused by varying
refractive index.

Kind of wierd to have AM/PM type fading in VHF and UHF bands.

Never heard of AM/PM fading, what is that ?

The
multiple antennas would point in very different directions. Not
single channel path diversity but per channel group separated antennas
pointed at the best signal (usually right at the transmit antenna but
not always).

While a few meters or some hundred MHz might be sufficient diversity
distance against frequency selective multipath problems, in order to
combat flat fading, the separation would have to be tens or hundreds
kilometers.

 

[JosephKK]

I would have loved to have had movies and a *large*, randomly accessible music
collection as I do today...

Now i gotta ask, how many albums/CDs or tracks is your large randomly
accessable (presumably on hard disk) music collection?

 

[JosephKK]

[email protected] wrote:

[...]

<snip>

I found that 56k connections only work very locally. When I did data
transfers across the pond a couple decades ago the most I could reliably
work at was 4800bd, sometimes 1200bd was required.
That makes no sense. The connection rate only depends on your "last mile".

This was in the days of point to point data transfer. Modules specs,
manuscripts, et cetera. Some of those connections went over "singing
wires" where the last mile could actually be more like 30 miles. You've
seen them, where the wires basically keep the poles from falling over.
Add in a crackling transatlantic connection with no SNR to write home about.

How did you get a cross-pond analog line at a time when there were 56K modems?

It wasn't a 56k modem. It was a 9600bd modem and later a 14.4k. But even
at that the connection would immediately error out unless I forced it to
start at 4800bd. It wouldn't have been any different with a 56k modem
unless it couldn't ratchet down to 2400 and 1200 (then you wouldn't be
able to connect). You can't beat Shannons theorem, when the channel is
weak there is nothing you can do except throttling down.

It depended a bit on the country. Germany-US would often hold 4800
through the whole session, but no more. For Germany-Canada it was
sometimes better to start even lower so it wouldn't cut out on me. Same
to Korea and places like that. But every reduction by a factor of two
meant a doubling of the costs of the call. Also, it was really important
to have a speaker run at least for the first 1/4 of the transmission.
That is because phone costs per minute were high back then and sometimes
it was smarter to cut it all loose after 5min and start over. Some
connections would gradually deteriorate for some reason and then you had
to try until you got one that didn't. After so many transmissions you
could almost predict whether a connection would stick or not.

We also split stuff up so partial reads would be useful and someone
could piece it back together at the other end. Sometimes when I hear
kids bemoan that the 5Mb/sec broadband at their parents' house is
sluggish I wish they could experience that old modem stuff just once.

If you had a >100k file and it wasn't super urgent it was cheaper to
spool it onto a floppy and airmail it.

Oldsters remember when bandwidth was expensive, like i "dimed up" and
downloaded the the packet drivers for early Ethernet cards from
Clarkson Uni to the Lost Angles area ar 2400 baud over a few nights,
cost me about $100 long distance for a little less than a MB. Now
that would be a few seconds and included (and would dissapear) in my
monthly. Today, a sloppy webpage will eat up a MB or more, and an
overnight DL would be about 5 GB; over 5 thousand times the data
volume. Just about 20 years difference.

 

[Joerg]

How about this news? A well known AM radio station lost all three
towers a few days ago. It was a well know country music station, with
its Wheeling Jamboree.

<http://www.wtrf.com/story.cfm?func=viewstory&storyid=83934>

<http://www.bing.com/search?q=+WWVA+tower+collapse&FORM=RCRE>

Very sad to look at those pictures. This could be the financial end of
WWVA :-(

 

[Joerg]

On a sunny day (Mon, 02 Aug 2010 15:08:20 -0700) it happened Joerg


Jan Panteltje wrote:
On a sunny day (Mon, 02 Aug 2010 13:36:19 -0700) it happened
<[email protected]>:
[...]

[...]

Right, do not pay for the advertising!

No, we fast forward through it. One box even has an advertising
FFW button that hops it 30sec at a time.
Good,. There exists soft with scene change detection too, IIRC.

Yeah, but it works well enough by hand. I am also rather good in
tuning it out in my head, reading up on stuff during the news when
the ads play.
Once I made the mistake to actually edit it out. Those are the
commercials I still remember, as I had to see them many times to get
start, and end, and audio, right in the editior

Very few ads remained in my gray cells. The only one I remember from the
six years I lived in NL is from Douwe Egberts "En dan is er koffie".

And also the source material counts, garbage in garbage out.

Dancing with the Stars from BBC is super material, you really
see a difference.
Now I am confused. If it was from BBC, then it must have been
original 25 fps . that reminds me of dropped frames and fast
pulldown, big problem with motion in a 30 fps country. Here the
movies just play 25 fps, no dropped frames, but they are slightly
shorter (original film was 24). The pitch of the audio is higher
too. http://www.24p.com/conversion.htm

Oh, Jan, we live in the 21st century. The times when such major
events were recorded in an analog format are long gone.
Cannot follow you here, BBC was recorded at 25 fps (tape) or 24 fps
(film). You play at 30 fps (or 60), so you have to interpolate frames
and add those at irregular intervals. I have some Linux soft for
that, it works, but the motion is not as smooth as at the original
speed I think. Do you think digital does not know about frame rate?
The problem we had here with LCD TVs (seems to go away with better
sets) was that many sets were HD compatible but displayed the 25 fps
material at 30 fps, causing horrible horizontal irregular jumping of
the picture.

This is what's cooking these days:

http://www.ikegami.com/br/products/hdtv/pdf/HDK77EX0401s.pdf

Most modern cameras can be switched so you can record in several native
frame rate standards:

http://www.ikegami.com/br/products/hdtv/hdtv_camera_frame1.html

I don't know how they do it but there is no interpolation at all. I
believe they record in US format because the participants are mostly
American, so it's for our market. The judges are one American, one
British and one (rather hot-blooded ...) Italian.

It's the level of the nerd factor. A big honking PC in the living
room requires one almost not to be married. A small one is ok, but
only if freshly married or close to the 50th anniversary
I think you still do not get the concept. I am not a fan of VDR, but
have a look at Klaus his website: http://www.tvdr.de/ It does not
have to be a 'big honking PC'. ...

It is pretty big. Anyhow, ours has the described features as well or
pretty close:

http://www.tvdr.de/software.htm

Except we have to swap out the disk after x hours. Ok, no big deal.

... My media centre PC is not in the
living room. There is no need for that, most modern TVs can access
files on the media server, via a menu (and ethernet). There are cheap
interface boxes available these days with HD output and ethernet
connection for any room you want. In fact, with all those standards
constantly changing, the best bet is to split everything up, monitor,
receiver, disks, DVD burner. At least something will be of use a bit
longer then the 2 to 5 years we now have between a system change, 3D
is here hoopla, we just had HD . Do you have your 3D set yet?

No, and no need to. Same with BlueRay. Since we are into older movies
and don't like games or scifi there would be no use for that here. We
rather spend that money at the Japanese restaurant, like today

Do you watch any TV on http://www.hulu.com

Not yet. Since the switch to DTV our TV consumption has gone down
significantly. And maybe that's a good thing

 

[Joerg]

[email protected] wrote:

[...]

<snip>

I found that 56k connections only work very locally. When I did data
transfers across the pond a couple decades ago the most I could reliably
work at was 4800bd, sometimes 1200bd was required.
That makes no sense. The connection rate only depends on your "last mile".
This was in the days of point to point data transfer. Modules specs,
manuscripts, et cetera. Some of those connections went over "singing
wires" where the last mile could actually be more like 30 miles. You've
seen them, where the wires basically keep the poles from falling over.
Add in a crackling transatlantic connection with no SNR to write home about.
How did you get a cross-pond analog line at a time when there were 56K modems?

It wasn't a 56k modem. It was a 9600bd modem and later a 14.4k. But even
at that the connection would immediately error out unless I forced it to
start at 4800bd. It wouldn't have been any different with a 56k modem
unless it couldn't ratchet down to 2400 and 1200 (then you wouldn't be
able to connect). You can't beat Shannons theorem, when the channel is
weak there is nothing you can do except throttling down.

It depended a bit on the country. Germany-US would often hold 4800
through the whole session, but no more. For Germany-Canada it was
sometimes better to start even lower so it wouldn't cut out on me. Same
to Korea and places like that. But every reduction by a factor of two
meant a doubling of the costs of the call. Also, it was really important
to have a speaker run at least for the first 1/4 of the transmission.
That is because phone costs per minute were high back then and sometimes
it was smarter to cut it all loose after 5min and start over. Some
connections would gradually deteriorate for some reason and then you had
to try until you got one that didn't. After so many transmissions you
could almost predict whether a connection would stick or not.

We also split stuff up so partial reads would be useful and someone
could piece it back together at the other end. Sometimes when I hear
kids bemoan that the 5Mb/sec broadband at their parents' house is
sluggish I wish they could experience that old modem stuff just once.

If you had a >100k file and it wasn't super urgent it was cheaper to
spool it onto a floppy and airmail it.

Oldsters remember when bandwidth was expensive, like i "dimed up" and
downloaded the the packet drivers for early Ethernet cards from
Clarkson Uni to the Lost Angles area ar 2400 baud over a few nights,

^^^^^^^^

Pun intended?

cost me about $100 long distance for a little less than a MB. Now
that would be a few seconds and included (and would dissapear) in my
monthly. Today, a sloppy webpage will eat up a MB or more, and an
overnight DL would be about 5 GB; over 5 thousand times the data
volume. Just about 20 years difference.

In those cases I'd rather send them a SASE envelope, a blank diskette
and $20 for the effoert to copy and the walk by the mail room. Then use
the remaining $80 for a nice dinner with the wife.

 

[Paul Keinanen]

How about this news? A well known AM radio station lost all three
towers a few days ago. It was a well know country music station, with
its Wheeling Jamboree.

Are you really saying that some radio broadcasting companies in the US
are still using medium wave AM as their main distribution channel ??

 

[Paul Keinanen]

Some? There are probably 10's of thousands of AM stations in the USA.
Your country is smaller than many/most of our states, so you don't
appreciate the need for "medium wave" to cover large areas.

Alaska, Texas and California have a larger land area than Finland, as
expected. However, I did not expect Montana to be also slightly
larger.

FM started here in the early 1950's and only a few people relied on AM
in the 1960's. In the 1990's medium wave AM was used to send news to
Finnish speaking emigrants in Sweden and to the Finnish speaking
minority in NE Russia.

Since those days, only hobby based low power (0.1 kW) AM transmitters
have been used during some selected weekends, mainly to support
DX-listeners.

To me, it is a surprise that medium wave AM is still actually used for
commercial broadcasting.

 

[Joerg]

Alaska, Texas and California have a larger land area than Finland, as
expected. However, I did not expect Montana to be also slightly
larger.

FM started here in the early 1950's and only a few people relied on AM
in the 1960's. In the 1990's medium wave AM was used to send news to
Finnish speaking emigrants in Sweden and to the Finnish speaking
minority in NE Russia.

Since those days, only hobby based low power (0.1 kW) AM transmitters
have been used during some selected weekends, mainly to support
DX-listeners.

To me, it is a surprise that medium wave AM is still actually used for
commercial broadcasting.

On long drives I listen to AM a lot. The reason is quite simple. The US
is such a large country and there are long stretches of land with very
sparse population. IOW not enough market for FM stations with their low
range. You can always find this or that local station but if their
programming is boring, well, then you must switch to the AM band. Also,
the smaller FM station tend to drift into the noise after only a few
country songs while AM stations usually stay around for hundreds of miles.

 

[[email protected]]

Jan Panteltje wrote:
On a sunny day (Mon, 02 Aug 2010 15:08:20 -0700) it happened Joerg


Jan Panteltje wrote:
On a sunny day (Mon, 02 Aug 2010 13:36:19 -0700) it happened
<[email protected]>:

[...]

[...]

Right, do not pay for the advertising!

No, we fast forward through it. One box even has an advertising
FFW button that hops it 30sec at a time.
Good,. There exists soft with scene change detection too, IIRC.

Yeah, but it works well enough by hand. I am also rather good in
tuning it out in my head, reading up on stuff during the news when
the ads play.
Once I made the mistake to actually edit it out. Those are the
commercials I still remember, as I had to see them many times to get
start, and end, and audio, right in the editior

Very few ads remained in my gray cells. The only one I remember from the
six years I lived in NL is from Douwe Egberts "En dan is er koffie".

And also the source material counts, garbage in garbage out.

Dancing with the Stars from BBC is super material, you really
see a difference.
Now I am confused. If it was from BBC, then it must have been
original 25 fps . that reminds me of dropped frames and fast
pulldown, big problem with motion in a 30 fps country. Here the
movies just play 25 fps, no dropped frames, but they are slightly
shorter (original film was 24). The pitch of the audio is higher
too. http://www.24p.com/conversion.htm

Oh, Jan, we live in the 21st century. The times when such major
events were recorded in an analog format are long gone.
Cannot follow you here, BBC was recorded at 25 fps (tape) or 24 fps
(film). You play at 30 fps (or 60), so you have to interpolate frames
and add those at irregular intervals. I have some Linux soft for
that, it works, but the motion is not as smooth as at the original
speed I think. Do you think digital does not know about frame rate?
The problem we had here with LCD TVs (seems to go away with better
sets) was that many sets were HD compatible but displayed the 25 fps
material at 30 fps, causing horrible horizontal irregular jumping of
the picture.

This is what's cooking these days:

http://www.ikegami.com/br/products/hdtv/pdf/HDK77EX0401s.pdf

Most modern cameras can be switched so you can record in several native
frame rate standards:

http://www.ikegami.com/br/products/hdtv/hdtv_camera_frame1.html

I don't know how they do it but there is no interpolation at all. I
believe they record in US format because the participants are mostly
American, so it's for our market. The judges are one American, one
British and one (rather hot-blooded ...) Italian.

It's the level of the nerd factor. A big honking PC in the living
room requires one almost not to be married. A small one is ok, but
only if freshly married or close to the 50th anniversary
I think you still do not get the concept. I am not a fan of VDR, but
have a look at Klaus his website: http://www.tvdr.de/ It does not
have to be a 'big honking PC'. ...
It is pretty big. Anyhow, ours has the described features as well or
pretty close:

http://www.tvdr.de/software.htm

Except we have to swap out the disk after x hours. Ok, no big deal.

... My media centre PC is not in the
living room. There is no need for that, most modern TVs can access
files on the media server, via a menu (and ethernet). There are cheap
interface boxes available these days with HD output and ethernet
connection for any room you want. In fact, with all those standards
constantly changing, the best bet is to split everything up, monitor,
receiver, disks, DVD burner. At least something will be of use a bit
longer then the 2 to 5 years we now have between a system change, 3D
is here hoopla, we just had HD . Do you have your 3D set yet?

No, and no need to. Same with BlueRay. Since we are into older movies
and don't like games or scifi there would be no use for that here. We
rather spend that money at the Japanese restaurant, like today

Do you watch any TV on http://www.hulu.com

Not yet. Since the switch to DTV our TV consumption has gone down
significantly. And maybe that's a good thing

Since we switched to DISH Network, our TV consumption hasn't gone down (the
end of the world wouldn't do that), but our frustration level has skyrocketed.
The city is proposing a venture into the cable TV and Internet market (the
network would be useful to the power company) and as much as I don't like such
things, I'm leaning towards it.

 

[[email protected]]

Only because the Obama administration and local tree huggers will
oppose the reconstruction.

Too bad it didn't happen last year. They could have named them the "Byrd
Towers" and had the taxpayers fork over for them. Maybe they could slide it
in the appropriations bill for NIST, between WWV and WWVB.

Amusing... when I lived in WV I didn't listen to WWVA, I listened to
the rock-n-roll stations in Huntington.

As a married student at MIT, early every morning I drove my wife to
work at Honeywell Datamatic and played WWVA in the car... very loud to
keep awake

Didn't think country would be your style.

 

[Joerg]

That's why I like satellite radio. The stretch of I8 from Gila Bend
to Yuma is devoid of FM and has only Mexican AM... although some of
their oom-pah-pah bands can be pretty entertaining... and their ads
are hilarious... all that shrieking, hooting and hollering ;-)

Ahora escuchen YUMAAAAAH! Ven al partido de futiboooooool EL DOMINGOOOOO!

 

[Joerg]

[snip]
On long drives I listen to AM a lot. The reason is quite simple. The US
is such a large country and there are long stretches of land with very
sparse population. IOW not enough market for FM stations with their low
range. You can always find this or that local station but if their
programming is boring, well, then you must switch to the AM band. Also,
the smaller FM station tend to drift into the noise after only a few
country songs while AM stations usually stay around for hundreds of miles.
That's why I like satellite radio. The stretch of I8 from Gila Bend
to Yuma is devoid of FM and has only Mexican AM... although some of
their oom-pah-pah bands can be pretty entertaining... and their ads
are hilarious... all that shrieking, hooting and hollering ;-)

Ahora escuchen YUMAAAAAH! Ven al partido de futiboooooool EL DOMINGOOOOO!

OK. You have that down-pat. I'll see if I can get you an announcing
job with KPAZ ;-)

Isn't KPAZ a religious station? Can't recall any Espanol on there but
it's been a while.