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Old 14th June 2012, 16:42   #21  |  Link
Poutnik
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Quote:
Originally Posted by Ghitulescu View Post
I assume there are video errors as well
Yes, but the sound ones are more disturbing, if occurs.

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I'd rather spend some hours in adjusting the antenna, rather than in encoding the audio (and/or video) with editing.
The other hundredds of inhabitants could try to kill me if I would tweak antennas, not mentioning I would not be allowed to.

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DVB-T has anyway such a low bitrate that makes transcoding into a "more compact" format merely a waste of time.
I would not say so. Encoding mpeg2 to H264 with comparable quality has about 1/3 - 1/4 size, with reasonable resize even more than 8times smaller. I would be out of space soon, not mentioning ads cutting.
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Old 15th June 2012, 16:14   #22  |  Link
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That I think either. Or from microwave oven, magnetrons or klystrons or whatever is inside can be very powerful in side effects.
Probably not - microwave oven is made as a Faraday cage - also magnetron is relatively narrow band RF source and front-end attenuate everything above 1GHz so for 2.4GHz overall attenuation should be quite high.

Switching large electric power without proper decoupling create spikes which have high energy and very high bandwidth. This can be compared at some point to EMP.

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Rare error people would not almost notice, will forgot,
or if not forgot, not remember to mention.

It would have be much worse for case otherwise.

BTW vendor TV application shows 7/7 dots of signal power.
Signal power is less important than BER (or "quality") - there can be high power signal with BER over 1.0E-4 and this mean visible and audible glitches.
My advice - instead of building common antenna installation, use home antenna, passive, no amplifier.

And also seems that You should be able to raise this problem to government authority responsible for quality of the RF spectrum - it is forbidden to corrupt RF signal - they should help you - this is mandatory for them - usually there special agency in telecommunication ministry - they searching for illegal transmitters but also they search for sources of such spikes.
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Old 16th June 2012, 13:25   #23  |  Link
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Probably not - microwave oven is made as a Faraday cage - also magnetron is relatively narrow band RF source and front-end attenuate everything above 1GHz so for 2.4GHz overall attenuation should be quite high.

Switching large electric power without proper decoupling create spikes which have high energy and very high bandwidth. This can be compared at some point to EMP.
I have meant rather along the power lines noise.
E.g. using digital video output from videocard, to monitor picture is fine. But during temporal period I used integrated intel graphics with analog output. At that time monitor picture was very eye-disturbing, if my microwave oven was working.

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My advice - instead of building common antenna installation, use home antenna, passive, no amplifier.
I am afraid my low floor location ad position away from signal,
without direct visibility and with reflection from other buildings will not be satisfactory.

I used initially a simple dipole, coming with my receiver,
but strength and quality was very poor. Than I bought room active antenna,
strength and quality better, but still not excellent.
The common source was much better.

All that struggles are not worthy for me to solve.
Either I can take the signal as it is,
either I fix it and I already know how.

Thanks all for the support.
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Old 16th June 2012, 20:46   #24  |  Link
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Just at the end of this discussion I'd like to add my two cents...

DVB-T receptionwise I think I am in a similar situation as Poutnik. I live on the first floor of an older 6-story building in the middle of Berlin, Germany. Basically good signal coverage, but my low location plus being surrounded by other high buildings make the reception a little problematic.

I uploaded a small sample of a typical audio glitch which neither ProjectX nor PVAStrumento can correct:
http://www.sendspace.com/file/xqzzkk

So far I have not found an automatic way to correct such glitches, the best I could get was using Sonic Foundry plugins (Vinyl Restoration and Click & Crackle Removal). But it is much easier to remove those spikes manually in a WAVE editor.


Still I'd like to share some tips how I improved my DVB-T captures considerably. The cost to put an antenna on my roof was prohibitive, so I did a lot of testing different antennas and some different tuners.

First of all I strongly disagree with Pandy when he discards active antennas. In all my tests active antennas delivered a higher quality signal compared to passive ones.

The real breakthrough for me was to use a diversity tuner. That's two separate tuners in one case which can be used in a way that one of the tuners corrects the signal of the other one. One tuner uses a directional antenna (Technisat Digitenne), the other one a simple omnidirectional antenna. Both antennas are spaced apart by about 2 meters.

Another problem for me was my slow computer. I don't know if this applies to you, but for a slower machine you should observe some things:

Capture in renderless mode. DVBViewer and DVBDream are my favorite capture programs. Also set priority to High and use a large recording buffer (Older versions of DVBViewer support this setting).

During capture disable your Internet connection and terminate all background software which could compromise I/O (like resident virus scanners).



Cheers
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Old 18th June 2012, 08:41   #25  |  Link
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Yes, diversity antennas are excellent for location with a lot of interferences (like your flat). However, one could try and fail to find a better position for the antenna (my antenna had such a strange position until I renounced at all at DVB-T).
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Old 18th June 2012, 12:47   #26  |  Link
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Quote:
Originally Posted by manolito View Post
First of all I strongly disagree with Pandy when he discards active antennas. In all my tests active antennas delivered a higher quality signal compared to passive ones.
don't get mi wrong manolito but active antenna = antenna + amplifier - issue with amplifiers in active antennas is that they are very cheap and without knowing parameters - if You really need amplifier go for some modern IC RF amplifiers or buy decent transistor amplifier (for me one of the most important parameters for RF amplifiers - "1dB compression point" also very important IP2 and IP3 - but good amplifiers are more expansive than cheap ones embedded in antenna). DVB-T is sensitive for saturated amplifier more than a analog receiver. Also power of signal (analog level) is less important than "signal quality" - medium level signal but with "quality" equal 100 is better than strong signal with "quality" 30%.

Not sure how you performed you tests but i know how antenna works and there is no magic - high gain passive antenna is ALWAYS better than low gain antenna with amplifier (there is no sens in amplifying noise and add noise from amplifier itself).

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Originally Posted by manolito View Post
The real breakthrough for me was to use a diversity tuner. That's two separate tuners in one case which can be used in a way that one of the tuners corrects the signal of the other one. One tuner uses a directional antenna (Technisat Digitenne), the other one a simple omnidirectional antenna. Both antennas are spaced apart by about 2 meters.
DVB-T is designed to deal and USE multipath reception - this means that there is no need eliminate reflections and at some special cases reflection can be better than direct reception.

COFDM with correct Guard Interval values can gain from many paths of signal. http://en.wikipedia.org/wiki/Orthogo...l_interference
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