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

Allen Edwards allen.p.edwards at gmail.com
Tue Jun 16 17:15:22 UTC 2009

On Tue, Jun 16, 2009 at 10:00 AM, Brian Wood<beww at beww.org> wrote:
> 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

Two questions come to mind.

1) Did the transition move your favorite channel from UHF to VHF and
you happen to have a UHF only antenna?  That happened in San Francisco
where KGO (channel 7) moved from channel 24 to really being on channel
7.  The solution to this is to either buy a combo antenna or make a
channel 7 only yagi and combine it.  I made one yesterday for a friend
for $13.

2) A good amplifier in the Channel Master 7777.  There is a great
discussion on amplifiers on this thread


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