[mythtv-users] Pre-amp for Hauppauge 1600

Dave Day david.scott.day at gmail.com
Sun May 16 05:06:20 UTC 2010

On 04/20/2010 08:16 PM, Douglas Peale wrote:
> Hash: SHA1
> Dave Day wrote:
>> I get about 7 local stations but only two of them are always good.
>> The two good ones are hi-band VHF.  Three others are good about 50% of
>> the time
>> and two others usually break up during a program.
> First go to TVFool.com and enter your location, see what it says about what you should be able to get and where to point your antenna.
> Second, get your antenna outside. There is all kinds of junk in your attic (power wiring, plumbing etc.) that makes it a horrible place for an antenna.
> The signal quality indicator on a TV is nearly useless for determining the cause of your problems.
> Every TV uses a different method of determining&  displaying signal quality, and most are terrible.
> With what you have, you can't tell if you signal problems are caused by weak signal, multi-path, or too strong signal.
> The information you get from TVFool will give you at least a clue as to the cause.
> The best tool I have for aiming antennas is the HDHomeRun Config tool that shows signal strength, signal quality, and symbol quality.
> Version: GnuPG v1.4.9 (GNU/Linux)
> Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
> jMYAn1WMnYw+Rrpao6mG0XNbZhSkRm7s
> =CiVV
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I have mostly solved the problem and thought an update might be useful 
to someone.

The bulk of responses to my original post indicated that a preamp should 
be postponed until after optimizing the other antenna system components, 
so I held off on that.

Instead I tried to learn a little about antennas.  My original antenna 
set up was a medium sized combination uhf/vhf antenna on a rotor in the 
attic at about 20 feet in height I'd guess.  The UHF portion is a small 
corner reflector yagi.  The VHF portion looks to be a log periodic type 
of antenna. Most of my transmitters are bunched together east of me 
about 25 miles away.  There are NO outside antennas within miles of me, 
so if possible, I wanted this to succeed in the attic.  The problem is 
we are deep in a forest of very tall pines and hardwoods.  Even if I do 
have to go outside the attic, I simply can't get above the trees.

This quote from above sums up my original situation:

I get about 7 local stations but only two of them are always good.
The two good ones are hi-band VHF.  Three others are good about 50% of
the time
and two others usually break up during a program.

I ended up building a single bay Gray-Hoverman (one hour at Home Depot 
and 3 hours at the work bench). The particular version I built is 
considered a UHF only antenna, so my plan was to first fix my main 
problem which was the UHF stations, and then I thought I would build a 
yagi for the two vhf ones.
Of course when I finished it I was anxious to get a hint of whether it 
would help.  So I went to the attic and just set the SBGH down on the 
attic floor under the rotor/antenna and moved the RG-6 coax to the balun 
on the Gray-Hoverman.  I pointed the SBGH in the general direction of my 
stations and went to check the reception.  It was great!  Apparently all 
the stations are pretty comfortably above the threshold where lock 
occurs because the pictures on all 7 stations are basically perfect.  
And, ironically, the two VHF stations are as good or better than they 
were before, even though the SBGH model I built is supposed to only be a 
UHF antenna.

Later in the day I switched out the original antenna and attached the 
Gray-Hoverman to the rotor.  Rotating the antenna some didn't seem to 
have a big effect on my reception, although I didn't go but 25 degrees 
in either direction.

So, needless to say, the Family Acceptance Factor has shot WAY up!  
Those 7 stations give us about 15 channels of programming and all of 
pretty much perfect quality, at least so far (Its only been two days).

But is does lead me to ask two questions.  I am using a Hauppauge 1600 
with MythTV.  Myth does not retrieve signal strength from that card.  It 
only gives what it calls SNR numbers which are generally between 2.1 and 
2.4.  I am left wondering if 2.4 is pretty much the best anybody ever 
gets from this card or would it be possible to get above 2.4 and perhaps 
give us some extra cushion for those rainy/windy days in the forest when 
signal quality varies?

Another interesting little fact is that before this Gray-Hoverman, when  
my experience was that an SNR number of 2.1 or less pretty much meant an 
unreliable lock and a pretty crappy viewing experience.  2.2 meant a 
better lock but some break up and pixellation, 2.3 meant we might get 
through the whole program with nor problems or we might not, but the 
viewing experience would be OK, and 2.4 meant whoohoo!  studio quality!

But now with the SBGH, I haven't had even the slightest problem even 
though the SNR does briefly go down even to 2.1.  The pictures have been 
solid even down there.  I don't really understand that.

So, I wonder if any of you all who have Hauppauge 1600s get SNRs above 
2.4 ???

And any thoughts on why with the SBGH the signal is good even with what 
before were pretty crappy SNR numbers.
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