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Antenna choice
PostPosted: Sun Nov 21, 2004 3:03 pm Reply with quote
dcarr178
 
Joined: 18 Nov 2004
Posts: 12
Location: West Jordan, Utah




When I run dtvscan /dev/dtv then all the channels zoom past and nothing gets detected. When I run dtvsignal on specific channels I know should be working in my area I get no signal whatsoever.

I've had so many driver issues that it has hard for me to believe the real problem might be my antenna. My HD-3000 card is connected to an attic-mounted external vhf/uhf/fm antenna that is 58 inches long, has 25 elements, and is rated for at 35 miles. I've had it for 6 years so I have no idea if it's rated for hdtv, although I have no reason to suspect it won't work. I live less than 10 miles from the hdtv broadcast towers. The antenna is not powered and I have a coax cable that goes from my attic to the basement where my htpc is. When I unplug my HD-3000 from the antenna and plug into a tv set, the tv finds ntsc channels just fine.

Does anybody have experience with a setup like this and could tell me whether my antenna should work or whether I should replace it?

I can't seem to even get ntsc channels with my HD-3000. Can anybody give me exact steps to put the card in ntsc mode and then use scantv or some other utility to find ntsc channels?
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Re: Antenna choice
PostPosted: Sun Nov 21, 2004 9:40 pm Reply with quote
maestro
 
Joined: 10 Jul 2004
Posts: 18




My only suggestion would be to check the quality of your UHF reception (channels 14+), since this is how almost all DTV stations are broadcast. (See http://en.wikipedia.org/wiki/UHF for a little more background on UHF.)

If you have good quality UHF reception, you shouldn't have a problem getting digital broadcasts.
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Re: Antenna choice
PostPosted: Mon Nov 22, 2004 10:43 am Reply with quote
Scott Larson
 
Joined: 15 Oct 2003
Posts: 713
Location: Portland, OR




dcarr178 wrote:
My HD-3000 card is connected to an attic-mounted external vhf/uhf/fm antenna that is 58 inches long, has 25 elements, and is rated for at 35 miles.

And is extremely directional. If it's not pointed directly at the towers, you're probably not going to get any detectable signal. I would verify that your antenna is pointed in exactly the right direction. Even if it is, move it around a little and see if you suddenly get flashes of signals.

I live only a few miles away from my local towers and I had to remove almost all of the elements from my antenna to get reliable reception from all the stations. It only had eight elements yet stations would disappear if it was pointed only a couple degrees away from them! Surprised
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Try to pipe it into a file.
PostPosted: Mon Nov 22, 2004 8:32 pm Reply with quote
cmumford
 
Joined: 07 Nov 2004
Posts: 36




I would run:

Code:
dvtscan /dev/dtv > ~/.xine/channels.atsc


and then look at your ~/.xine/channels.atsc file. I suspect that this will contain some of the channel information for your area.

I have written a program that will essentially run dtvsignal on each channel listed in channels.atsc file and report its signal level. If there is any interest in this then I will post it for others to use.
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Antenna working great
PostPosted: Sat Nov 27, 2004 12:07 pm Reply with quote
dcarr178
 
Joined: 18 Nov 2004
Posts: 12
Location: West Jordan, Utah




I bought a little internal hdtv antenna with 45db gain from WalMart so I could test a liittle bit. I found out the right direction to point it in and ended up getting pretty good signals. Then I went back to my large outdoor antenna (mounted in my attic) and pointed it the right way. Now I get 21 channels with 95% or higher strength. I didn't even have to break off any antenna elements.

When dtvsignal says I have 95% or higher signal strength, any idea why mythtv sould say I only have 34%? From /var/log/mythtv/mythtvbackend.log:

2004-11-27 11:08:07 mythbackend: MythBackend started as master server
2004-11-27 11:08:08 Maximum signal strength detected: 34% after 5500 msec wait
2004-11-27 11:08:09 mythbackend version: 0.16.20040906-1 www.mythtv.org
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Problem found
PostPosted: Sat Nov 27, 2004 12:43 pm Reply with quote
dcarr178
 
Joined: 18 Nov 2004
Posts: 12
Location: West Jordan, Utah




Nevermind. I had my channels configured wrong iin mythsetup. By the way, this is the most convoluted setup channel setup ever but it's working. I found helpful hints at

http://www.mythtv.info/moin.cgi/ATSC
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Re: Antenna working great
PostPosted: Sun Nov 28, 2004 1:31 am Reply with quote
Scott Larson
 
Joined: 15 Oct 2003
Posts: 713
Location: Portland, OR




dcarr178 wrote:
Now I get 21 channels with 95% or higher strength. I didn't even have to break off any antenna elements.

Crazy how it sometimes helps to be farther away from stations. I could get all of my stations over 95% if I could aim my antenna at them but instead I have to aim the antenna right between two clusters of towers. Fortunately I still get them all 80%-90% which is still nearly flawless reception.
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PostPosted: Sun Nov 28, 2004 2:06 pm Reply with quote
bradtem
 
Joined: 18 Nov 2004
Posts: 6




Antenna choice is an interesting problem. Right now almost all HDTV is on UHF. In the Bay Area it's all UHF except for KNTV-NBC which is on VHF 12. However, since I am only about 12 miles from their tower I can get them fine on a UHF Yagi.

Those big giant antennas tend to be for VHF. They will have a small yagi at the front (with wings going up and down) which is their UHF antenna. Some people don't realize it but if you want just UHF you just need the Yagi at the front, so don't buy the rest if you don't need it. Radio Shack has a nice UHF Yagi for $22.

However, it is true that _eventually_, the stations are going to be told to give up their analog broadcasts. This is years away, and they want it to be even further away, so they keep lobbying for it. (The old standard would never have been reached but they didn't win the fight to keep it.)

When this happens they must choose one of their two channels. There are reasons to keep the digital one but other reasons to keep the VHF one (if they have one) and switch it to digital.

So when this happens you may wish you put up a giant VHF antenna or you may say, "I'll just swap then when it happens."

Another good UHF antenna is multiple bowties against a reflector. Some people put up as many as 16 bowties.

However, counter to all this is that cable companies are starting to offer digital HD stations in QAM format on the cable. My cable company does this though (illegally) they are not providing every digital station, just the majors. pchdtv has said they will offer QAM support in the 3000 card. If they do, you can just plug into the cable.

And let's face it, over the air stations are now only a small part of the TV picture, and any serious TV user is going to want cable or satellite on top of their Digital OTA TV. If you go cable, you probably won't need your antenna.

(Unfortunately, most of the QAM signals will be encrypted, only the ones you can get from antenna are required to be unencrypted. Right now however, Comcast is providing ESPN-HD unencrypted.)
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PostPosted: Mon Nov 29, 2004 10:13 am Reply with quote
Scott Larson
 
Joined: 15 Oct 2003
Posts: 713
Location: Portland, OR




OTA stations are a large part of the HDTV picture right now. If you don't subscribe to premium channels, you'll only get four or five more HD channels on most cable systems and they don't have a fraction of the original HD content that the networks have. I pay fifty bucks a month to get one more NFL game a week when I get at least three HD games OTA for free. The rest of my cable channels are recycled network reruns or low budget productions.

Plus who says cable companies are going to make it easy to receive anything on their systems? People are having tpns of trouble using QAM cards hooked up to cable right now. People are finding that even their local stations are encrypted (no comment from the companies) and many unencrypted streams change frequencies and subchannels every day. The hundreds of non-local digial channels you may subscribe to will be encrypted. They don't want you downloading this content to your computer.

My Comcast encrypts EPSN-HD and Discovery-HD.
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Antenna choice
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