DTV antennas?

See the data sheet at:

Units with antenna: % of the standard, V/m, A/m, W/m2, mW/cm2, dBVm, dBmV/m, dBA/m, dBµV/m Units without antenna: dBV/m, dBmV/m, dBµV/m, dBm Isotropic Measurements (etc...). Kinda looks like field strength and power density.

Ok. There was no way to determine that from the pattern.

I see. So if I'm inside the 41dBu contour, I get great reception but if I'm just outside the 41dBu contour, I get lousy reception. A single line isn't very useful.

Personally, I prefer a series of contours, complete with shadows and local detail. Here's a really awful example of the wide area coverage for a propose ham radio VHF repeater:

(I'll post some better stuff there when I find where I buried my work disk). Also, for cell sites (near bottom of page):

That's my recommendation. No TV for me for almost 20 years and I'm not at all inclined to change it. And I live in a house where my wife _does_ watch. I'm never even tempted to sit by her at those times and watch. Other things perhaps, while she is occupied, yes. But not watch the TV.

Jon

On a sunny day (Sat, 12 Jul 2008 06:47:22 -0700) it happened Joerg wrote in :

Actually I wonder about all those DTV problems. I would have though that you, Joerg, with all your RF experience and radio amateur experience?, would have dealt with that issue long time ago. I mean, with all respect, one can measure field strength, shield reflections, find a suitable antenna etc. If it then is clear there is a true problem and reception is not possible, write to your representative...

As to the search and find no more channels, that is why I use an USB DVB-T receiver and the PC (disk) for recording, It is easy to scan, and of course I made a backup of the best scan list I got, Also easy to port that list to an other PC, and easy to stream over the net around the house, or around the world wherever you are, so you do not have to miss you pet programs, Of course this did not all occur to me on the first day I received a digital signal. But I can even steer the satellite dish from anywhere in the world. It is nice, this afternoon ITV1 had one of those old Cliff Richard movies, 'Summer Holiday', just recorded it remotely and streamed it via TCP/IP.

Maybe take these remarks as hints, also for the others, complaining sucks, solutions are much better,

Analog degrades very gracefully. But we had situations where analog was nearly perfect yet almost all digital channels croaked.

BTDT. You can get Ch40 to come in perfectly but then you lose Ch13. Get Ch13 perfect and you lose Ch29. And so on. With analog that was not the case.

I'll wait until Feb 2009 when all the frequencies are re-assigned and (hopefully) the DTV signal of the main stations scoot over to VHF. If it's still the pits I will sure write.

The missus won't like a PC in the living room :-)

What is your boom length Jorge?

Cheers

Jeff, I've spent a career creating, reviewing, and analyzing RF propagation maps. I agree the one you posted (of the amateur station) is pretty hard to read.

As for the single contour, you can't say with certainty that past the line there will no reception. In fact, there will be. And, inside the lines there will also be places with no coverage. But 41dBu of signal is sufficient for adequate coverage - absent any weird stuff.

Also, the dBu requirement changes slightly by frequency. Keep that in mind.

What you might need is a full study, using the tighest topo data and calculation grids you can live with - but even that won't give you indoor reception. For that, you'd need extensive ray-tracing models, etc..., and frankly by that point, you're more likely to invest in an outdoor antenna on a pole, or cable / satellite, etc...

For cell sites, remember they are more concerned about adjacent channel re-use (and interference with CDMA systems, etc..) , not maximum RF coverage. So generally, cell site plots much more resolution than broadcast to be of any practical use.

tions,

le,

B-T

Another piece of potential fall-out from all this DTV switchover:

I wonder how much attention is being given to hurricane prone coastlines and the need to receive news and weather updates while the power is out??

How many of us own portable DTV's? Probably well below 1%. If the power goes out, (and you dont' have a generator), the cable, satellite and DTV converter boxes all stop working. After 2009, turn on your portable TV and you'll find it doesn't work either.

I spoke to a Chief Engineer at a Miami station a month or so ago, and he claims that after 2009, they won't even have the exciter equipment available to switch back to analog during a hurricane disaster (assuming the FCC would permit it, which they probably would?) It all boils down to economics. They don't want to pay extra tower antenna space for anything related to analog after they turn it off. So the transmitter goes, the antenna and transmission line goes, etc...

And presumably, they will have stopped upconversion by then and be digital end-to-end, though I seriously doubt it!

Exactly. When (not if) cable and power go away for a week or so, it's all-the-way with OTA. I guess it's back to radio days.

Amazon lists a couple but they're "currently unavailable."

Remind me to bug you when I have a propogation problem. No good deed is every left unpunished.

Yep. My study sucks, but it's is the only one that I could find on my PC that covers a wide area. The others are worse. The non-perspective version is somewhat easier to read. I did some fast cleanup, shrank the files a bit, and reposted them at:

Incidentally, KG6NRI had just entered high skool at the time when he moved to Prundale and wanted to know the coverage from his new house. I cranked out those propagation studies for him. However, he also thought they stunk and did his own. See:

I'll post some more examples as I find them.

However, this isn't about me. It's about Jeorg and his DTV problem. A bit of digging shows that he lives in Cameron Park, CA.

which shows a lat-long of 38.676389N -120.989444W. Plugging into:

at a range of 75 miles, there are DTV stations on 18, 21, 26, 35, 43,

A few are losers because their antenna patterns are in the wrong direction. The eliminates 26 and 43. Look at the "Transmitter Antenna" column for how it works.

Jeorg... which channels do you want to watch?

My point exactly.

Sitting behind a small hill or obstruction is not "weird stuff". I run into it every day. That's why I use the SRTM digital topo maps and such to get as much detail and accuracy as possible. I dunno if the 41dBu contour are sufficient to determine if one can use rabbit ears or if one requires an outside directional antenna and rotator. I kinda prefer to know the approximate signal strength in the vicintiy. However, I will agree that the 41dBu contours are sufficient demonstrate to advertisers that they can reliably cover the included area. Also for defining the protected area for cochannel, adjacent channel, and alternate channel protection.

Yep. They're F(50/90) noise limited contours. 41dBu UHF 36dBu VHF-H 28dBu VHF-L

Yep. However, Jeorg is not doing indoor reception. He's doing outdoor, presumeably with a directional yagi or log periodic, possibly with an amplifier.

I think he's already made the investment. I've never tried the ray tracing models, mostly because I've never needed that level of accuracy. For a rooftop DTV antenna, methinks the SRTM 1 arc second topo maps are good enough.

From my limited experience, the cellular companies seem to be more interested in minimizing the number of cell sites and fudging the results to make it look like they coverage in areas where it's marginal. The propagation prediction programs are able to generate detailed levels of signal strength. The junk I posted has 12 levels of signal strength. Yet the posted cellular coverage maps frequently have much less granularity with perhaps 3 levels being most common.

I hear you, Joerg. I haven't been totally happy with digital. In May I bought one o' them thar "boxes" to keep my 1983 Sony TV useful. I can see the transmitter towers (4 TV, several AM and FM) from the sidewalk, about 3 miles up the valley, so I never used an outdoor or attic antenna for analog, and I don't now that I'm digital either. I get the Picasso thing from time to time (appropriate description; thanks!). Be interesting to see what happens when the seasons change, trees become bare. In analog days fierce wind storms during leaf seasons messed up reception... thrashing trees between transmitter hill and my UHF loop.

I heard someone cheerfully say that, with digital, there's no ghosting and no snow as with analog, that you either receive it or you don't. Which is true, but .... misleading.

I've never had cable nor satellite, always freebie TV via loop/rabbit ears, so upon seeing my first (stable) digital proggie on the old TV I felt like doing a Snoopy dance.

On a sunny day (Sat, 12 Jul 2008 16:32:39 -0700 (PDT)) it happened mpm wrote in :

Not to worry, few more years and you will all have cell phones with DVB-T (terrestrial). It is the latest thing in Europe, or maybe 'outside the US':

The local telco has them for free with 10 Euro / month (15 $) or so extra on the cellphone subscription IIRC. For the rest the programs are free, but then you py in full for the phone.

etc.

There is also the DVB-H standard (for broadcasting to Hand-held devices) that has found some favour in trials in the UK.

As far as I was aware, there has been no take up of the standards of the DVB consortium in the USA (different needs or NIH).

Chris

On a sunny day (Sun, 13 Jul 2008 16:40:34 +0100) it happened "christofire" wrote in :

Yes, DVB-H is recommended by the European Union, however with free DVB-T and things like football available on DVB-T, DVB-H may well die because of lack of investor interest. (DVB-H would be a pay service).

Yes, but once Europe buys the US for 1$ that may well change ;-)

You can buy that here. It's called TiVo box and neighbors who have one said it'll automatically adjust record times if, for example, a football game runs into overtime and the movie is delayed. We are fine with ye olde VCR. When it dies we prbably buy a DVD recorder but only if there isn't too much DRM stuff to render it useless. IOW as long as it does what the VCR does, record movie we missed because we aren't home.

It's here as well. But only for kids. The eyes at 40+ aren't up to snuff for such small screens anymore.

It'll be a shift towards cell phone and POTS. Reverse 911 and all that. Anyhow, in a disaster I wouldn't trust anything but my old AM radio. What good does it do to have a portable analog TV, DTV or cell phone if the batteries quit after a very short time?

Sounds like the converter boxes. Out here the drill is: Call the stores every day and when one has supply be ready for a mad dash.

Now wait a minute, that is a rather personal ... oh, you mean the yagi? That is about 10ft, the first five being the UHF part and the rear 5ft is the log periodic for VHF I/III. ChannelMaster, biggest honking antenna money could buy back then.

Yawn. You couldn't scrape up a dollar, anywhere in Europe, because all of Europe isn't worth two cents.