[mythtv-users] Increasing ATSC signal strength going into DVB card

Brian Wood beww at beww.org
Tue Jun 16 17:00:53 UTC 2009

On Tuesday 16 June 2009 10:41:55 MythTV wrote:
> Ever since the decommission of NTSC, my ATSC signal strength has been
> about 30% lower than before across all channels.  Unfortunately, the
> channel we watch the most now only has a signal strength of 11% which
> is not enough for MythTV to lock on nor record from.  Before July
> 12th, our favorite channel had a signal strength 51%.
> I do have a signal amplifier on my antenna cable. It's a Blonder
> Tongue Broadband VHF/FM/UHF Distribution Amplifier.  I've been told
> that it is good enough for my area but I'll change if there's a
> better one to use.  Here's the URL to my amplifier:
> http://www.sjmediasystem.com/zta-15.html
> I also have a Digital Converter box connected to the same splitter
> where both pcHDTV HD-5500 cards are connected; the converter reports
> a signal strength of 40% on the channel in question where MythTV
> reports only 11%.
> I have tried changing the direction of my antenna.  No luck.
> Is there a way to increase the signal strength going into the pcHDTV
> HD-5500? Or, is there a way to make the pcHDTV HD-5500 more sensitive
> to the signal it is being fed?

The unit you pointed to is a "distribution" amplifier. Such amplifiers are 
designed to drive a distribution system (makes sense, huh?). IOW they are 
designed to make up for the losses in splitters and cables in a distribution 
system, not to improve low-level signals from an antenna, that job is usually 
done with an "antenna pre-amplifier", which is usually mounted as close to 
the antenna as possible.

A distribution amp will be sufficient in areas of fairly good signal strength, 
but is not the best solution in remote areas,

I wouldn't pay too much attention to the signal strengths reported by various 
devices. There is no standard for such measurements, and even different units 
from the same maker tend to be different. The BER is a more consistent 
indication of signal quality. Most tuners want a level of zero to +10 dbmv. 
(per channel), an amplifier can increase levels, but generally can't increase 
the quality of the signal. Amplifiers can also introduce distortion products, 
especially if you have a strong local TV or FM signal that overloads the amp. 
You can use tunable notches or bandstop filters to lower the level of local 
signals to that of distant channels.

I've read that capture cards require more signal than TV sets, but I doubt 
this. They must use off-the-shelf tuners like TV set makers use, I don;t 
think they designed a tuner specifically for the card, especially one that 
is "worse" than commercially available units.

I'd consider mounting a pre-amp on your antenna mast. Sorry I'm not familiar 
with current products. so I can't give you a pointer.

Make sure none of the stations you receive have moved as part of the 
changeover, if they did your antenna might be pointed in the wrong direction.

Brian Wood
beww at beww.org

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