[mythtv-users] HDHomerun signal strength required

[Roger Heflin]

Brian Wood wrote:
ts.
> backuppc at sundquist.imapmail.org wrote:
>> Another related question:  My daughter sometimes may want to play an old
>> VHS tape or two we have laying around.  I am not converting these all to
>> DVDs.   Our VHS player outputs to coax on NTSC channel 3.  I could have
>> the pcHDTV card (which does NTSC as well as ATSC) pick that up (right?).
> 
> The pcHDTV card is a digital and an analog tuner, but the analog tuner 
> is a simple frame grabber, thus you will have to encode using your CPU. 
> Myth will record your VHS tape, though it's a bit of overkill. Myth only 
> supports RTJpeg or MPEG4 with a frame grabber card, the former is 
> suggested unless you have a fast CPU.
> 
>> Could I plug that into a 1:4 splitter, effectively making it a 2:3
>> splitter?  Another way to pose that question is "even though four of the
>> five F-plugs say `out' (see
>> http://rsk.imageg.net/graphics/product_images/pRS1C-2265543w345.jpg) are
>> all five in fact wired in parallel?"
> 
> I would not do that. Although a hybrid splitter will act as a combiner 
> (backwards) you might (actually almost certainly will) wind up 
> transmitting the channel 3 signal out your antenna, causing outfits like 
> the FCC to take an interest in your activity.

I don't believe that they are actually wired in parallel, the RC circuit is
carefully setup so each of the 4 outs get the same signal, having one
of the out's be an in would likely get some odd reflections (ie ghosts)
on the other outs.  Besides like Brian says, you may get some unwanted
attention from the FCC.

> 
>> I actually have a merger up in the attic of two directional UHF
>> antennas, so I am probably looking at all kinds of efficiency losses.
>> Should I consider a signal amplifer after the merge?  My DTV signal
>> strength could be better.
> 
> Combining two or more antennas can work, and is often done, but you have 
> to be sure you have the phasing correct, and this will be affected by 
> things like cable length (inches make a difference).

I have 2 directional antenna's combined with a splitter and it works decent,
I probably have decent luck simply because the 2 signal sources are almost
exactly 180 degrees apart, so the interference from the one antenna picking
up the other antenna's channels is minimal, I have a mast type amp after
that and then a attenuator to cut the signal down before the distribution 
amplifier, too much signal causes poor analog and digital signals.    Whether
you need an amplifier or not depends on how far you are from the signals,
and you may need to lower the signal strength to get things to work after
the amp (if you do get adjustable attenuators, it is pretty easy to adjust
things to maximize the signal quality), also the mast type amplifiers are 
supposed to have a lot better 1st stage (less noise, cleaner) than most tuners 
since tuners don't need to be any good any more since few are using them for OTA.

The distribution amplifier I have allows the modulation of 2 house channels
and put the mythtv stuff on that so I can watch the channels anywhere
in the house (the good tv has a direct svideo connection), and I have
things to relay the remote signals to the actual remote receiver.   The
modulation device does 2 channels audio + composite in, and gives a decent
enough picture for older tv's.

                                  Roger