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Receiver Sensitivity
PostPosted: Thu Mar 02, 2006 2:00 pm Reply with quote
laramie
 
Joined: 02 Mar 2006
Posts: 3
Location: Georgia, USA




What's the sensitivity of the receiver in the HD-3000? How strong of a signal is necessary to get a good bistream out of it?

Laramie

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HD-3000, Intel Pentium 4 3.2 GHz, 1 GB RAM
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PostPosted: Thu Apr 27, 2006 8:48 am Reply with quote
skow
 
Joined: 27 Apr 2006
Posts: 14




I'm not really qualified to answer the question since I haven't been using the card for very long, but I think I read somewhere that 70% is considered to give a consistent picture. I think if you use the dtvsignal the ascii image gives you an indication of what it thinks of your signal. You want to see a line of dollar signs ($$$$$) which means your signal is good.

Sorry I can't give you much more of an objective answer, but I figured some feedback is better than no feedback. I suspect, however, that after nearly 2 months you have given up on the question or found your answer.
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PostPosted: Thu Apr 27, 2006 12:03 pm Reply with quote
laramie
 
Joined: 02 Mar 2006
Posts: 3
Location: Georgia, USA




Thanks for the response. I had given up on getting an answer.

I'm really looking for a specific value in units such as milliwatts that the card needs in order to reliably decode a good stream of data from.

My goal is to be able to do link margin calculations, taking in all variables to include transmitter power, transmitter antenna gain, distance from transmitter to my antenna, my antenna gain, my cable loss, etc.

The point of that is to figure out which of the stations in my area I *should* be able to receive from my location with my given antenna and such, using standard engineering practices.

Laramie

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PostPosted: Thu Apr 27, 2006 12:31 pm Reply with quote
skow
 
Joined: 27 Apr 2006
Posts: 14




Ah, I see. I think the best one could do is get a 'theoretical' list of what you should be able to receive, which I think antennaweb.org sort of does. Other factors such as terrain (hills, plains, mountains, forest, etc), elevation, other buildings blocking or reflecting signals would become more of an influence.

Another factor to getting a stable stream is the signal to noise ratio. Regardless of how strong of a signal is needed, if you've got a lot of noise the picture quality will suffer or fail all together.

Since you are obviously technically inclined and I have done nothing above to further answer your question, one thing you might consider is finding some way to measure what the actual signal strength you are receiving on a particular station is measured in milliwatts. With that, you can then use dtvsignal to see what 'percent' signal the card sees. Those two numbers then provide you with the HD3000's percent/mw. So, for easy calculation, say 1%==1mw therefore the card would need 70mw to give a reliable picture assuming my initial information of 70 is correct.

Unfortunately, I'm not familiar enough with the equipment available for signal measurement and can not suggest a particular device that would allow you to hook it up to your antenna input, choose a frequency band, and see the exact milliwatts you are getting. Hopefully it at least gives you some ideas on what to try.

Ideally, the card or tuner manufacturer would be able to give you a 'real' technical specification on required signal power and acceptable S/N ratios...
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PostPosted: Fri Apr 28, 2006 7:46 pm Reply with quote
dieter
 
Joined: 20 Jan 2005
Posts: 43
Location: US




laramie wrote:
Thanks for the response. I had given up on getting an answer.

I'm really looking for a specific value in units such as milliwatts that the card needs in order to reliably decode a good stream of data from.

My goal is to be able to do link margin calculations, taking in all variables to include transmitter power, transmitter antenna gain, distance from transmitter to my antenna, my antenna gain, my cable loss, etc.

The point of that is to figure out which of the stations in my area I *should* be able to receive from my location with my given antenna and such, using standard engineering practices.

Laramie


Unless you are trying to pick up deep fringe stations, the signal level is unlikely to be a significant problem. If you don't have a strong enough signal, a preamp or distribution amp (Channel Master or Winegard, not RadioShack. For super deep fringe consider Research Communications) will likely give you plenty. If you have too much, an attenuator will throw some away. I have been experimenting with amps and attenuators and get the same performance from the HD-3000 over at least a 52 dB range. Instead, worry about the following:

1) multipath
2) multipath
3) multipath
4) interferrence
5) multipath
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Receiver Sensitivity
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