DTV antennas?

On Jul 13, 7:39=EF=BF=BDam, Jan Panteltje wrote= :

V_MOB...

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Oh yeah, like that's really going to help!?!

After Hurricane Katrina slammed the Louisiana Coast, one carrier (I won't mention their name), had nearly 200 cell sites out of commission. I suspect the others were equally affected, particularily since many share the same towers due to restrictive zoning and other concerns.

These outages ranged from no-power, to no circuits (T1, etc..), to no antenna & tower!!

And to add, that same carrier called me later that day to ask about resources for refueling their diesel & propane emergency standby generators. Evidently, they foolishly believed their sites were "good" because they were originally constructed with standby power generation. Unfortunately, they hadn't given all that much thought to the need to continuously re-fuel these things on a wide-spread basis under emergency conditions....

The result: Sure, the cell sites that survived the hurricane remained on the air -- until their generators died from lack of fuel, and the cell site batteries gave out. (Note: Same effect as not having any of this stuff in the first place.)

On Jul 13, 1:13=EF=BF=BDpm, Jan Panteltje wrote= :

T_TV_MOB...

=EF=BF=BDextra

one.

d.

But it would translator stations, not repeaters in any event. I'm not sure where we are at licensing those. Presumably, all the top markets got their analog translator & booster stations licensed for DTV already. The rest, including the low power stuff (that's a guess), might have to wait until DTV maximization is complete?? For example, some of this MediaFLO stuff on Ch-55 that's tied into the 700 MHz auction is really difficult to follow. If I had more interest in it, I guess I would commit the cycles to understanding it bettter.

In any event, it will be very interesting to see how much fallout there is in 2009 from the switchover -- or will this just be like another Year-2000 hype issue?

And _all_ of it was W's fault ;-)

...Jim Thompson

I'm not conversant in OTA DTV since I'm on cable, but I see a local station (ABC, ch15) advertising their OTA HD is on ch15.2

What's that ".2" all about?

...Jim Thompson

On a sunny day (Sun, 13 Jul 2008 11:18:32 -0700 (PDT)) it happened mpm wrote in :

Well DVB-T does _not_ go via the cellphone towers. It goes via some big transmitters covering a huge area. Unless much of Netherlands floods, something will be on the air,

Sure those things are designed to keep going for maybe 24 or 48 hours.. Old POTS was that way here anyways, with big 48V batteries.

As to my personal situation I have a 150 W shortwave and battery power to send SOS for an hour, or normal CB for 12 Hours 'we are on the roof, please send a boat' sort of thing. Radios no problem, TV? who cares in an emergency,

Carriers, do not get me started, just found Vodafne's name servers failed, I could only reach sites by typing the IP address... After nnnn reconnects the log shows they changed name servers.

Well the US is a bit more wild then this part of Europe I think. But nothing lasts forever, we will have to know how to survive with as only food source a little garden, and daylight to see by. As in Russia. Now, if the infrastructures fail, people in the world will die thousands at the time, especially in the cities.

Summaries like this aren't too accurate. I believe they do not take into account topograhical issues such as mountain ridges. Some like Ch 3, 10,

Again, multipath is the big issue with ATSC.

Yes, a BIG yagi plus mast amp, head distribution amp, the works.

They usually do not publish detailed coverage maps but they should. The only way to find out is aksk around who uses which carrier and how it works. That's what I did.

Here is another blunder of the TV set designers: They ignored the fact that you do not have any means of optimizing an antenna with DTV. The signal is either fairly good or gone. IOW digital. No field strength indicators, no signal quality bars, nada. IMHO a design blunder. Oh man, if we did that in medical they'd have us all over the barrel.

The DTV channel bandwidth is the same as analog TV. However, since DTV is compressed, the station can cram up to about 5 program channels into the same bandwidth. So, you get 15.1, 15.2 ... 15.5, each with their own seperate programming. Looking at:

it appears that 15.1 is just a clone of the current analog content. It doesn't look like they have seperate programming on the other DTV "channels". Some (not all) of the digital channels are in HDTV.

In Europe, COFDM works well with mobile video. In the US, 8VSB is close to useless. There were several parking lot demos of "enhancements" to 8VSB at NAB in April (I wasn't there), that were not very impressive. The OMVC:

is trying to put something workable together for the ATSC to look at. Several big companies are working on the problem, each with their own patent pending enhancements. Final approval is allegedly due in Feb

Note the mobile TV will be on a different digital sub-channel as regular programming, mostly because the required screen resolution is much less than that of a typical home TV. If you're planning on watching 1080p on your PDA or cell phone, forget it.

There seems to be quite a bit of interest among the major manufacturers. My guess(tm) is that the spectacular sucess of the iPod and iPhone may be the driving force behind selling mobile video.

There are some samples on YouTube. Search for "mobile TV".

Ok, I lied. KNXV has two digital channels. See:

If you wanna go cheap, get a USB ATSC TV tuner and plug it into your computah. Then, you can watch TV as you umm.... work.

We'll probably buy a bunch of tape soon before it's extinct. The VCR got a converter box so it'll keep working until its head assembly falls off.

Out here it seems to be so. Kids spend an incredible amount of their parent's money on communication.

Well, yeah, but it does get old. I even had to get the glasses to be able to set the thermostat or the irrigation timer.

No, its only 15 miles. But anything past that ridge is a problem.

That's what nearly all of them do. Some have five channels and the upper two are often in Spanish. Once in a while you can catch a classy old movie. Really old John Wayne and stuff. But it's hit and miss because there is no reliable source for programming info.

Once when we just got the converter boxes I checked it again in the evening after setting it up. Sure enough, a super Western on 65-4 or whatever. In Spanish but I could understand enough to follow. Man was I tired the next moring.

News and stuff can also be viewed online. I think there is a serious chance that all this DTV is just a phase and it'll be all via IP some day.

Sorry. I mis-spelled your name.

Yep, major goof. However, it's not universal. Some hidden TV diagnostics show signal strength, error rate, SNR, etc. Also, some PC based receivers have signal strength:

There are also independent signal strength meters which might be useful:

I use an ancient Texscan 7272 meter and some CATV equipment for measuring signal strength.

BITE (built in test equipment) is a mixed bag. I've included it in several products, only to have marketing demand that it be removed because they didn't want to supply calibration data or argue over the numbers. However, production loved it because it makes final test and QA very easy.

"Nothing beats line-of-sight" for coverage!! Which is a good thing for deep space telemetry!

I have to admit I am surprised that the US DTV system is quite so sensitive to multipath. Or do you really live in a very challenging reception environment where analogue signals show massive ghosting too?

My parents analogue signal is terrible - football shows two blokes for every player on the field, and a deep flyback rectangle and yet their (UK) DTV works fine. They don't like it because the old familiar Ceefax data service isn't supported but that is a different matter.

I have noticed a weaker signal in midsummer with wet leaves on the trees after a rainstorm. Humidity never really a problem here.

So what sort of signal levels are you seeing after the pre-amp ?

And the Yagi and preamp combo is good to cover the entire band and not overloaded by some local strong signal causing intermodulation.

Are you sure about that? The European set top boxes and digital TVs show a signal quality 0..10 that indicates a crude measure of the raw bit error rate. Or at least all the ones I have seen and played with do.

The nicer ones also do signal strength and quality for a channel in realtime. It will only do it in tuning or engineer mode in the setup/tuning/DVB signal quality menu path. First generation hardware only shows the "quality" (with no idication of signal strength).

Mostly they show 10/10 where I live since I have line of sight on a powerful transmitter - wet string would probably get me enough signal.

If it really is multipath from fixed objects and you are prepared to mess around with more complex aerial configurations then you might be able to make some progress by having 2 (or more) identical aerials in an equal interferometer configuration. That way you should with a suitable choice of spacing be able to place a null on the strongest most damaging multipath reflection. Unfortunately it will be wavelength dependent.

If you have the patience then spacings that work well with small numbers of aerials as a simple phased array are

All of these populate every integer multiple of baseline upto and including the longest.

I suspect if you cost your time it would be much cheaper ot get a satellite feed, but if you are doing it for the challenge of making the thing work despite the technology defects then this might give you a sporting chance of nulling out some of the multipath interference.

Good luck!

Regards, Martin Brown

On a sunny day (Sun, 13 Jul 2008 13:27:28 -0700) it happened Joerg wrote in :

That is why I designed my tuning soft so it looks like this: ftp://panteltje.com/pub/xdipo2.jpg Note the 4 green squares. 'L' for lock, 'V' for Viterbi, etc.. The pie chart is dynamic, almost like the old 'green eye' EM34? tuning indicator on the AM radio from my youth. Also there is a 'BEEP" button, when pressed it creates a beep with frequency related to signal strength, put speaker in window, align dish. It can run without GUI from a script, and it shows free disk space too. I see a lot lot downloads for 'xdipo', it is here (Linux GPL):

:-)

On a sunny day (Sun, 13 Jul 2008 14:05:06 -0700) it happened Jeff Liebermann wrote in :

I think one more reason that system may not gain acceptance. Here DVB-T will give full resolution (about the same a the display you use), and that is needed too, as for example the Dutch use subtitles (text along the bottom side of the screen) for all foreign movies / languages, and that text needs to be readable. If the subtitle is tranmitted on a different PID it would be digital, and would probably work, but if it is 'embedded' in a movie then you need good resolution.

Apple, and Steve Jobs: I see it like this: If Steve Jobs started selling frozen s*it one of these days as the latest thing with an Apple logo on it, then his apple-devoties would buy it and say: 'Actually tastes different, but it is APPLE.'

I do not have an ipod, iphone, whatever, and do not want or need one, I prefer buttons to rubbing a screeen.

And his latest iphone does not even have DVB-T !

Not that challenging. Analog works fine out here. I guess ATSC was never thoroughly field tested. They surely did not afford the same diligence we are used to in medical.

Same here, Humidity rolls in, DTV channels keel over one by one.

Don't remember but plenty for analog. Had to notch down Ch19 and Ch29 because TV set designers seem to be unable to grasp what dynamic range means.

Not here. Unless there is a secret code like hit button x four times when the black cat crosses the street etc.

Plus we are in the approach path of the Mather freight hub plus we have a local runway pretty much next to the house. Airplanes change multipath drastically.

Or we might just give up TV ;-)

I'd prefer what some analog TVs had, a big huge bar on the screen. You can easily see that while on the ladder turning the antenna.

The lack of a signal indicator in TV sets seems to be epidemic. However, I didn't think about the add-on boxes. All satellite receivers have signal indicators allegedly for dish alignment (which is useless because of the long response time). CATV converters have on screen signal level indications. A few boxes have more detailed diagnostics.

ATSC converter boxes require some manner of signal quality indicator:

See: Section 4.7 Consumer Interface Received Signal Quality Indicator I read it to indicate that while a detailed signal quality indicator would be nice, a really crude like a "good/bad" indicator will suffice.

Section 4.2 and 4.5 cover multipath tests and issues.

It kinda makes sense to have the signal level and quality indicator in the receiver (downconverter) section. However, why the same feature is absent in OTA DTV's seems rather odd.