[mythtv-users] Signal strength, DVB-T

[Daniel Kristjansson]

On Sun, 2008-02-03 at 14:29 -0800, Brad DerManouelian wrote:
> On Feb 3, 2008, at 2:16 PM, Bruce Richardson wrote:
> 
> > On Sat, Feb 02, 2008 at 12:55:13PM -0500, Tom Dexter wrote:
> >> If the signal strength you're referring to in mythtv is the one that
> >> momentarily appears in the OSD when you change channels, I think that
> >> (at least in 0.20.2 with my HD-5500 cards) there might be some sort  
> >> of
> >> timing issue with the way mythtv reads that strength.  Mine sometimes
> >> even shows zero.  However, if I actually display the strength by
> >> either using the F7 key in mythtv or using a separate program (I use
> >> femon a lot) it'll be anywhere from 60 to 95.
> >
> > I see the same signal strength figures when changing to a channel,  
> > when
> > pressing F7 or when using tzap.  All of these tell me that I am seeing
> > signal strengths of 28 to 35% and yet the picture is clear and it's  
> > all
> > working.  I think that might be an issue with the driver or firmware.
> 
> Signal strength has little to do with signal quality.
> I wish I could link to the page I read about it but I can't find it  
> now. Basically, it said that signal strength means pretty much  
> nothing. Signal quality is the real measurement of number of good  
> packets vs. errors.

Signal strength is only one factor in signal quality. It's the one
that helps you aim your antenna so it is pretty valuable for that
reason. But adding an amplifier to get a better signal strength can
in fact lead to lower signal quality.

Also with the Linux DVB drivers the signal strength is not calibrated
to the actual signal strength wattage, so a 35% on one card may be
equivalent to 75% on another card. It is only the relative % seen
on a single piece of hardware between different channels or antenna
pointing directions which tell you anything worth while.

-- Daniel